## 1. Life and works



Immanuel Kant was born April 22, 1724 in Konigsberg, near the
southeastern shore of the Baltic Sea. Today Konigsberg has been
renamed Kaliningrad and is part of Russia. But during Kant's
lifetime Konigsberg was the capital of East Prussia, and its
dominant language was German. Though geographically remote from the
rest of Prussia and other German cities, Konigsberg was then a
major commercial center, an important military port, and a relatively
cosmopolitan university
 town.[1]



Kant was born into an artisan family of modest means. His father was a
master harness maker, and his mother was the daughter of a harness
maker, though she was better educated than most women of her social
class. Kant's family was never destitute, but his father's
trade was in decline during Kant's youth and his parents at
times had to rely on extended family for financial support. 



Kant's parents were Pietist and he attended a Pietist school,
the Collegium Fridericianum, from ages eight through fifteen. Pietism
was an evangelical Lutheran movement that emphasized conversion,
reliance on divine grace, the experience of religious emotions, and
personal devotion involving regular Bible study, prayer, and
introspection. Kant reacted strongly against the forced soul-searching
to which he was subjected at the Collegium Fridericianum, in response
to which he sought refuge in the Latin classics, which were central to
the school's curriculum. Later the mature Kant's emphasis
on reason and autonomy, rather than emotion and dependence on either
authority or grace, may in part reflect his youthful reaction against
Pietism. But although the young Kant loathed his Pietist schooling, he
had deep respect and admiration for his parents, especially his
mother, whose "genuine religiosity" he described as
"not at all enthusiastic." According to his biographer,
Manfred Kuehn, Kant's parents probably influenced him much less
through their Pietism than through their artisan values of "hard
work, honesty, cleanliness, and independence," which they taught
him by
 example.[2]




Kant attended college at the University of Konigsberg, known as
the Albertina, where his early interest in classics was quickly
superseded by philosophy, which all first year students studied and
which encompassed mathematics and physics as well as logic,
metaphysics, ethics, and natural law. Kant's philosophy
professors exposed him to the approach of Christian Wolff
(1679-1750), whose critical synthesis of the philosophy of G. W.
Leibniz (1646-1716) was then very influential in German
universities. But Kant was also exposed to a range of German and
British critics of Wolff, and there were strong doses of
Aristotelianism and Pietism represented in the philosophy faculty as
well. Kant's favorite teacher was Martin Knutzen
(1713-1751), a Pietist who was heavily influenced by both Wolff
and the English philosopher John Locke (1632-1704). Knutzen
introduced Kant to the work of Isaac Newton (1642-1727), and his
influence is visible in Kant's first published work,
*Thoughts on the True Estimation of Living Forces* (1747),
which was a critical attempt to mediate a dispute in natural
philosophy between Leibnizians and Newtonians over the proper
measurement of force.



After college Kant spent six years as a private tutor to young
children outside Konigsberg. By this time both of his parents had
died and Kant's finances were not yet secure enough for him to
pursue an academic career. He finally returned to Konigsberg in
1754 and began teaching at the Albertina the following year. For the
next four decades Kant taught philosophy there, until his retirement
from teaching in 1796 at the age of seventy-two.



Kant had a burst of publishing activity in the years after he returned
from working as a private tutor. In 1754 and 1755 he published three
scientific works - one of which, *Universal Natural History
and Theory of the Heavens* (1755), was a major book in which,
among other things, he developed what later became known as the
nebular hypothesis about the formation of the solar system.
Unfortunately, the printer went bankrupt and the book had little
immediate impact. To secure qualifications for teaching at the
university, Kant also wrote two Latin dissertations: the first,
entitled *Concise Outline of Some Reflections on Fire* (1755),
earned him the Magister degree; and the second, *New Elucidation of
the First Principles of Metaphysical Cognition* (1755), entitled
him to teach as an unsalaried lecturer. The following year he
published another Latin work, *The Employment in Natural Philosophy
of Metaphysics Combined with Geometry, of Which Sample I Contains the
Physical Monadology* (1756), in hopes of succeeding Knutzen as
associate professor of logic and metaphysics, though Kant failed to
secure this position. Both the *New Elucidation*, which was
Kant's first work concerned mainly with metaphysics, and the
*Physical Monadology* further develop the position on the
interaction of finite substances that he first outlined in *Living
Forces*. Both works depart from Leibniz-Wolffian views, though not
radically. The *New Elucidation* in particular shows the
influence of Christian August Crusius (1715-1775), a German
critic of
 Wolff.[3]



As an unsalaried lecturer at the Albertina Kant was paid directly by
the students who attended his lectures, so he needed to teach an
enormous amount and to attract many students in order to earn a
living. Kant held this position from 1755 to 1770, during which period
he would lecture an average of twenty hours per week on logic,
metaphysics, and ethics, as well as mathematics, physics, and physical
geography. In his lectures Kant used textbooks by Wolffian authors
such as Alexander Gottlieb Baumgarten (1714-1762) and Georg
Friedrich Meier (1718-1777), but he followed them loosely and
used them to structure his own reflections, which drew on a wide range
of ideas of contemporary interest. These ideas often stemmed from
British sentimentalist philosophers such as David Hume
(1711-1776) and Francis Hutcheson (1694-1747), some of
whose texts were translated into German in the mid-1750s; and from the
Swiss philosopher Jean-Jacques Rousseau (1712-1778), who
published a flurry of works in the early 1760s. From early in his
career Kant was a popular and successful lecturer. He also quickly
developed a local reputation as a promising young intellectual and cut
a dashing figure in Konigsberg society.



After several years of relative quiet, Kant unleashed another burst of
publications in 1762-1764, including five philosophical works.
*The False Subtlety of the Four Syllogistic Figures* (1762)
rehearses criticisms of Aristotelian logic that were developed by
other German philosophers. *The Only Possible Argument in Support
of a Demonstration of the Existence of God* (1762-3) is a
major book in which Kant drew on his earlier work in *Universal
History* and *New Elucidation* to develop an original
argument for God's existence as a condition of the internal
possibility of all things, while criticizing other arguments for
God's existence. The book attracted several positive and some
negative reviews. In 1762 Kant also submitted an essay entitled
*Inquiry Concerning the Distinctness of the Principles of Natural
Theology and Morality* to a prize competition by the Prussian
Royal Academy, though Kant's submission took second prize to
Moses Mendelssohn's winning essay (and was published with it in
1764). Kant's *Prize Essay*, as it is known, departs more
significantly from Leibniz-Wolffian views than his earlier work and
also contains his first extended discussion of moral philosophy in
print. The *Prize Essay* draws on British sources to criticize
German rationalism in two respects: first, drawing on Newton, Kant
distinguishes between the methods of mathematics and philosophy; and
second, drawing on Hutcheson, he claims that "an unanalysable
feeling of the good" supplies the material content of our moral
obligations, which cannot be demonstrated in a purely intellectual way
from the formal principle of perfection alone
 (2:299).[4]
 These themes reappear in the *Attempt to Introduce the Concept of
Negative Magnitudes into Philosophy* (1763), whose main thesis,
however, is that the real opposition of conflicting forces, as in
causal relations, is not reducible to the logical relation of
contradiction, as Leibnizians held. In *Negative Magnitudes*
Kant also argues that the morality of an action is a function of the
internal forces that motivate one to act, rather than of the external
(physical) actions or their consequences. Finally, *Observations on
the Feeling of the Beautiful and the Sublime* (1764) deals mainly
with alleged differences in the tastes of men and women and of people
from different cultures. After it was published, Kant filled his own
interleaved copy of this book with (often unrelated) handwritten
remarks, many of which reflect the deep influence of Rousseau on his
thinking about moral philosophy in the mid-1760s.



These works helped to secure Kant a broader reputation in Germany, but
for the most part they were not strikingly original. Like other German
philosophers at the time, Kant's early works are generally
concerned with using insights from British empiricist authors to
reform or broaden the German rationalist tradition without radically
undermining its foundations. While some of his early works tend to
emphasize rationalist ideas, others have a more empiricist emphasis.
During this time Kant was striving to work out an independent
position, but before the 1770s his views remained fluid.



In 1766 Kant published his first work concerned with the possibility
of metaphysics, which later became a central topic of his mature
philosophy. *Dreams of a Spirit-Seer Elucidated by Dreams of
Metaphysics*, which he wrote soon after publishing a short
*Essay on Maladies of the Mind* (1764), was occasioned by
Kant's fascination with the Swedish visionary Emanuel Swedenborg
(1688-1772), who claimed to have insight into a spirit world
that enabled him to make a series of apparently miraculous
predictions. In this curious work Kant satirically compares
Swedenborg's spirit-visions to the belief of rationalist
metaphysicians in an immaterial soul that survives death, and he
concludes that philosophical knowledge of either is impossible because
human reason is limited to experience. The skeptical tone of Dreams is
tempered, however, by Kant's suggestion that "moral
faith" nevertheless supports belief in an immaterial and
immortal soul, even if it is not possible to attain metaphysical
knowledge in this domain (2:373).



In 1770, at the age of forty-six, Kant was appointed to the chair in
logic and metaphysics at the Albertina, after teaching for fifteen
years as an unsalaried lecturer and working since 1766 as a
sublibrarian to supplement his income. Kant was turned down for the
same position in 1758. But later, as his reputation grew, he declined
chairs in philosophy at Erlangen (1769) and Jena (1770) in hopes of
obtaining one in Konigsberg. After Kant was finally promoted, he
gradually extended his repertoire of lectures to include anthropology
(Kant's was the first such course in Germany and became very
popular), rational theology, pedagogy, natural right, and even
mineralogy and military fortifications. In order to inaugurate his new
position, Kant also wrote one more Latin dissertation: *Concerning
the Form and Principles of the Sensible and Intelligible World*
(1770), which is known as the *Inaugural Dissertation*.



The *Inaugural Dissertation* departs more radically from both
Wolffian rationalism and British sentimentalism than Kant's
earlier work. Inspired by Crusius and the Swiss natural philosopher
Johann Heinrich Lambert (1728-1777), Kant distinguishes between
two fundamental powers of cognition, sensibility and understanding
(intelligence), where the Leibniz-Wolffians regarded understanding
(intellect) as the only fundamental power. Kant therefore rejects the
rationalist view that sensibility is only a confused species of
intellectual cognition, and he replaces this with his own view that
sensibility is distinct from understanding and brings to perception
its own subjective forms of space and time - a view that
developed out of Kant's earlier criticism of Leibniz's
relational view of space in *Concerning the Ultimate Ground of the
Differentiation of Directions in Space* (1768). Moreover, as the
title of the *Inaugural Dissertation* indicates, Kant argues
that sensibility and understanding are directed at two different
worlds: sensibility gives us access to the sensible world, while
understanding enables us to grasp a distinct intelligible world. These
two worlds are related in that what the understanding grasps in the
intelligible world is the "paradigm" of "NOUMENAL
PERFECTION," which is "a common measure for all other
things in so far as they are realities." Considered
theoretically, this intelligible paradigm of perfection is God;
considered practically, it is "MORAL PERFECTION" (2:396).
The *Inaugural Dissertation* thus develops a form of Platonism;
and it rejects the view of British sentimentalists that moral
judgments are based on feelings of pleasure or pain, since Kant now
holds that moral judgments are based on pure understanding alone.



After 1770 Kant never surrendered the views that sensibility and
understanding are distinct powers of cognition, that space and time
are subjective forms of human sensibility, and that moral judgments
are based on pure understanding (or reason) alone. But his embrace of
Platonism in the *Inaugural Dissertation* was short-lived. He
soon denied that our understanding is capable of insight into an
intelligible world, which cleared the path toward his mature position
in the *Critique of Pure Reason* (1781), according to which the
understanding (like sensibility) supplies forms that structure our
experience of the sensible world, to which human knowledge is limited,
while the intelligible (or noumenal) world is strictly unknowable to
us. Kant spent a decade working on the *Critique of Pure
Reason* and published nothing else of significance between 1770
and 1781. But its publication marked the beginning of another burst of
activity that produced Kant's most important and enduring works.
Because early reviews of the *Critique of Pure Reason* were few
and (in Kant's judgment) uncomprehending, he tried to clarify
its main points in the much shorter *Prolegomena to Any Future
Metaphysics That Will Be Able to Come Forward as a Science*
(1783). Among the major books that rapidly followed are the
*Groundwork of the Metaphysics of Morals* (1785), Kant's
main work on the fundamental principle of morality; the
*Metaphysical Foundations of Natural Science* (1786), his main
work on natural philosophy in what scholars call his critical period
(1781-1798); the second and substantially revised edition of the
*Critique of Pure Reason* (1787); the *Critique of Practical
Reason* (1788), a fuller discussion of topics in moral philosophy
that builds on (and in some ways revises) the *Groundwork*; and
the *Critique of the Power of Judgment* (1790), which deals
with aesthetics and teleology. Kant also published a number of
important essays in this period, including *Idea for a Universal
History With a Cosmopolitan Aim* (1784) and *Conjectural
Beginning of Human History* (1786), his main contributions to the
philosophy of history; *An Answer to the Question: What is
Enlightenment?* (1784), which broaches some of the key ideas of
his later political essays; and *What Does it Mean to Orient
Oneself in Thinking?* (1786), Kant's intervention in the
pantheism controversy that raged in German intellectual circles after
F. H. Jacobi (1743-1819) accused the recently deceased G. E.
Lessing (1729-1781) of Spinozism.



With these works Kant secured international fame and came to dominate
German philosophy in the late 1780s. But in 1790 he announced that the
*Critique of the Power of Judgment* brought his critical
enterprise to an end (5:170). By then K. L. Reinhold
(1758-1823), whose *Letters on the Kantian Philosophy*
(1786) popularized Kant's moral and religious ideas, had been
installed (in 1787) in a chair devoted to Kantian philosophy at Jena,
which was more centrally located than Konigsberg and rapidly
developing into the focal point of the next phase in German
intellectual history. Reinhold soon began to criticize and move away
from Kant's views. In 1794 his chair at Jena passed to J. G.
Fichte, who had visited the master in Konigsberg and whose first
book, *Attempt at a Critique of All Revelation* (1792), was
published anonymously and initially mistaken for a work by Kant
himself. This catapulted Fichte to fame, but soon he too moved away
from Kant and developed an original position quite at odds with
Kant's, which Kant finally repudiated publicly in 1799
(12:370-371). Yet while German philosophy moved on to assess and
respond to Kant's legacy, Kant himself continued publishing
important works in the 1790s. Among these are *Religion Within the
Boundaries of Mere Reason* (1793), which drew a censure from the
Prussian King when Kant published the book after its second essay was
rejected by the censor; *The Conflict of the Faculties* (1798),
a collection of essays inspired by Kant's troubles with the
censor and dealing with the relationship between the philosophical and
theological faculties of the university; *On the Common Saying:
That May be Correct in Theory, But it is of No Use in Practice*
(1793), *Toward Perpetual Peace* (1795), and the *Doctrine
of Right*, the first part of *The Metaphysics of Morals*
(1797), Kant's main works in political philosophy; the
*Doctrine of Virtue*, the second part of *The Metaphysics of
Morals* (1797), Kant's most mature work in moral philosophy,
which he had been planning for more than thirty years; and
*Anthropology From a Pragmatic Point of View* (1798), based on
Kant's anthropology lectures. Several other compilations of
Kant's lecture notes from other courses were published later,
but these were not prepared by Kant himself.



Kant retired from teaching in 1796. For nearly two decades he had
lived a highly disciplined life focused primarily on completing his
philosophical system, which began to take definite shape in his mind
only in middle age. After retiring he came to believe that there was a
gap in this system separating the metaphysical foundations of natural
science from physics itself, and he set out to close this gap in a
series of notes that postulate the existence of an ether or caloric
matter. These notes, known as the *Opus Postumum*, remained
unfinished and unpublished in Kant's lifetime, and scholars
disagree on their significance and relation to his earlier work. It is
clear, however, that some of these late notes show unmistakable signs
of Kant's mental decline, which became tragically precipitous
around 1800. Kant died February 12, 1804, just short of his eightieth
birthday.


## 2. Kant's project in the *Critique of Pure Reason*



The main topic of the *Critique of Pure Reason* is the
possibility of metaphysics, understood in a specific way. Kant defines
metaphysics in terms of "the cognitions after which reason might
strive independently of all experience," and his goal in the
book is to reach a "decision about the possibility or
impossibility of a metaphysics in general, and the determination of
its sources, as well as its extent and boundaries, all, however, from
principles" (Axii. See also Bxiv; and 4:255-257). Thus
metaphysics for Kant concerns a priori knowledge, or knowledge whose
justification does not depend on experience; and he associates a
priori knowledge with reason. The project of the *Critique* is
to examine whether, how, and to what extent human reason is capable of
a priori knowledge.


### 2.1 The crisis of the Enlightenment



To understand the project of the *Critique* better, let us
consider the historical and intellectual context in which it was
 written.[5]
 Kant wrote the *Critique* toward the end of the Enlightenment,
which was then in a state of crisis. Hindsight enables us to see that
the 1780's was a transitional decade in which the cultural
balance shifted decisively away from the Enlightenment toward
Romanticism, but Kant did not have the benefit of such hindsight.



The Enlightenment was a reaction to the rise and successes of modern
science in the sixteenth and seventeenth centuries. The spectacular
achievements of Newton in particular engendered widespread confidence
and optimism about the power of human reason to control nature and to
improve human life. One effect of this new confidence in reason was
that traditional authorities were increasingly questioned. Why should
we need political or religious authorities to tell us how to live or
what to believe, if each of us has the capacity to figure these things
out for ourselves? Kant expresses this Enlightenment commitment to the
sovereignty of reason in the *Critique*:



> 
> Our age is the age of criticism, to which everything must submit.
> Religion through its holiness and legislation through its majesty
> commonly seek to exempt themselves from it. But in this way they
> excite a just suspicion against themselves, and cannot lay claim to
> that unfeigned respect that reason grants only to that which has been
> able to withstand its free and public examination. (Axi)
> 



Enlightenment is about thinking for oneself rather than letting others
think for you, according to *What is Enlightenment?* (8:35). In
this essay, Kant also expresses the Enlightenment faith in the
inevitability of progress. A few independent thinkers will gradually
inspire a broader cultural movement, which ultimately will lead to
greater freedom of action and governmental reform. A culture of
enlightenment is "almost inevitable" if only there is
"freedom to make public use of one's reason in all
matters" (8:36).



The problem is that to some it seemed unclear whether progress would
in fact ensue if reason enjoyed full sovereignty over traditional
authorities; or whether unaided reasoning would instead lead straight
to materialism, fatalism, atheism, skepticism (Bxxxiv), or even
libertinism and authoritarianism (8:146). The Enlightenment commitment
to the sovereignty of reason was tied to the expectation that it would
not lead to any of these consequences but instead would support
certain key beliefs that tradition had always sanctioned. Crucially,
these included belief in God, the soul, freedom, and the compatibility
of science with morality and religion. Although a few intellectuals
rejected some or all of these beliefs, the general spirit of the
Enlightenment was not so radical. The Enlightenment was about
replacing traditional authorities with the authority of individual
human reason, but it was not about overturning traditional moral and
religious beliefs.



Yet the original inspiration for the Enlightenment was the new
physics, which was mechanistic. If nature is entirely governed by
mechanistic, causal laws, then it may seem that there is no room for
freedom, a soul, or anything but matter in motion. This threatened the
traditional view that morality requires freedom. We must be free in
order to choose what is right over what is wrong, because otherwise we
cannot be held responsible. It also threatened the traditional
religious belief in a soul that can survive death or be resurrected in
an afterlife. So modern science, the pride of the Enlightenment, the
source of its optimism about the powers of human reason, threatened to
undermine traditional moral and religious beliefs that free rational
thought was expected to support. This was the main intellectual crisis
of the Enlightenment. 



The *Critique of Pure Reason* is Kant's response to this
crisis. Its main topic is metaphysics because, for Kant, metaphysics
is the domain of reason - it is "the inventory of all we
possess through pure reason, ordered systematically" (Axx)
- and the authority of reason was in question. Kant's main
goal is to show that a critique of reason by reason itself, unaided
and unrestrained by traditional authorities, establishes a secure and
consistent basis for both Newtonian science and traditional morality
and religion. In other words, free rational inquiry adequately
supports all of these essential human interests and shows them to be
mutually consistent. So reason deserves the sovereignty attributed to
it by the Enlightenment.


### 2.2 Kant's Copernican revolution in philosophy



To see how Kant attempts to achieve this goal in the
*Critique*, it helps to reflect on his grounds for rejecting
the Platonism of the *Inaugural Dissertation*. The
*Inaugural Dissertation* also tries to reconcile Newtonian
science with traditional morality and religion in a way, but its
strategy is different from that of the *Critique*. According to
the *Inaugural Dissertation*, Newtonian science is true of the
sensible world, to which sensibility gives us access; and the
understanding grasps principles of divine and moral perfection in a
distinct intelligible world, which are paradigms for measuring
everything in the sensible world. So on this view our knowledge of the
intelligible world is a priori because it does not depend on
sensibility, and this a priori knowledge furnishes principles for
judging the sensible world because in some way the sensible world
itself conforms to or imitates the intelligible world.



Soon after writing the *Inaugural Dissertation*, however, Kant
expressed doubts about this view. As he explained in a February 21,
1772 letter to his friend and former student, Marcus Herz:



> 
> In my dissertation I was content to explain the nature of intellectual
> representations in a merely negative way, namely, to state that they
> were not modifications of the soul brought about by the object.
> However, I silently passed over the further question of how a
> representation that refers to an object without being in any way
> affected by it can be possible.... [B]y what means are these
> [intellectual representations] given to us, if not by the way in which
> they affect us? And if such intellectual representations depend on our
> inner activity, whence comes the agreement that they are supposed to
> have with objects - objects that are nevertheless not possibly
> produced thereby?...[A]s to how my understanding may form for
> itself concepts of things completely a priori, with which concepts the
> things must necessarily agree, and as to how my understanding may
> formulate real principles concerning the possibility of such concepts,
> with which principles experience must be in exact agreement and which
> nevertheless are independent of experience - this question, of
> how the faculty of understanding achieves this conformity with the
> things themselves, is still left in a state of obscurity.
> (10:130-131)
> 



Here Kant entertains doubts about how a priori knowledge of an
intelligible world would be possible. The position of the
*Inaugural Dissertation* is that the intelligible world is
independent of the human understanding and of the sensible world, both
of which (in different ways) conform to the intelligible world. But,
leaving aside questions about what it means for the sensible world to
conform to an intelligible world, how is it possible for the human
understanding to conform to or grasp an intelligible world? If the
intelligible world is independent of our understanding, then it seems
that we could grasp it only if we are passively affected by it in some
way. But for Kant sensibility is our passive or receptive capacity to
be affected by objects that are independent of us (2:392, A51/B75). So
the only way we could grasp an intelligible world that is independent
of us is through sensibility, which means that our knowledge of it
could not be a priori. The pure understanding alone could at best
enable us to form representations of an intelligible world. But since
these intellectual representations would entirely "depend on our
inner activity," as Kant says to Herz, we have no good reason to
believe that they would conform to an independent intelligible world.
Such a priori intellectual representations could well be figments of
the brain that do not correspond to anything independent of the human
mind. In any case, it is completely mysterious how there might come to
be a correspondence between purely intellectual representations and an
independent intelligible world.



Kant's strategy in the *Critique* is similar to that of
the *Inaugural Dissertation* in that both works attempt to
reconcile modern science with traditional morality and religion by
relegating them to distinct sensible and intelligible worlds,
respectively. But the *Critique* gives a far more modest and
yet revolutionary account of a priori knowledge. As Kant's
letter to Herz suggests, the main problem with his view in the
*Inaugural Dissertation* is that it tries to explain the
possibility of a priori knowledge about a world that is entirely
independent of the human mind. This turned out to be a dead end, and
Kant never again maintained that we can have a priori knowledge about
an intelligible world precisely because such a world would be entirely
independent of us. However, Kant's revolutionary position in the
*Critique* is that we can have a priori knowledge about the
general structure of the sensible world because it is not entirely
independent of the human mind. The sensible world, or the world of
appearances, is constructed by the human mind from a combination of
sensory matter that we receive passively and a priori forms that are
supplied by our cognitive faculties. We can have a priori knowledge
only about aspects of the sensible world that reflect the a priori
forms supplied by our cognitive faculties. In Kant's words,
"we can cognize of things a priori only what we ourselves have
put into them" (Bxviii). So according to the *Critique*,
a priori knowledge is possible only if and to the extent that the
sensible world itself depends on the way the human mind structures its
experience.



Kant characterizes this new constructivist view of experience in the
*Critique* through an analogy with the revolution wrought by
Copernicus in astronomy:



> 
> Up to now it has been assumed that all our cognition must conform to
> the objects; but all attempts to find out something about them a
> priori through concepts that would extend our cognition have, on this
> presupposition, come to nothing. Hence let us once try whether we do
> not get farther with the problems of metaphysics by assuming that the
> objects must conform to our cognition, which would agree better with
> the requested possibility of an a priori cognition of them, which is
> to establish something about objects before they are given to us. This
> would be just like the first thoughts of Copernicus, who, when he did
> not make good progress in the explanation of the celestial motions if
> he assumed that the entire celestial host revolves around the
> observer, tried to see if he might not have greater success if he made
> the observer revolve and left the stars at rest. Now in metaphysics we
> can try in a similar way regarding the intuition of objects. If
> intuition has to conform to the constitution of the objects, then I do
> not see how we can know anything of them a priori; but if the object
> (as an object of the senses) conforms to the constitution of our
> faculty of intuition, then I can very well represent this possibility
> to myself. Yet because I cannot stop with these intuitions, if they
> are to become cognitions, but must refer them as representations to
> something as their object and determine this object through them, I
> can assume either that the concepts through which I bring about this
> determination also conform to the objects, and then I am once again in
> the same difficulty about how I could know anything about them a
> priori, or else I assume that the objects, or what is the same thing,
> the experience in which alone they can be cognized (as given objects)
> conforms to those concepts, in which case I immediately see an easier
> way out of the difficulty, since experience itself is a kind of
> cognition requiring the understanding, whose rule I have to presuppose
> in myself before any object is given to me, hence a priori, which rule
> is expressed in concepts a priori, to which all objects of experience
> must therefore necessarily conform, and with which they must agree.
> (Bxvi-xviii)
> 



As this passage suggests, what Kant has changed in the
*Critique* is primarily his view about the role and powers of
the understanding, since he already held in the *Inaugural
Dissertation* that sensibility contributes the forms of space and
time - which he calls pure (or a priori) intuitions (2:397)
- to our cognition of the sensible world. But the
*Critique* claims that pure understanding too, rather than
giving us insight into an intelligible world, is limited to providing
forms - which he calls pure or a priori concepts - that
structure our cognition of the sensible world. So now both sensibility
and understanding work together to construct cognition of the sensible
world, which therefore conforms to the a priori forms that are
supplied by our cognitive faculties: the a priori intuitions of
sensibility and the a priori concepts of the understanding. This
account is analogous to the heliocentric revolution of Copernicus in
astronomy because both require contributions from the observer to be
factored into explanations of phenomena, although neither reduces
phenomena to the contributions of observers
 alone.[6]
 The way celestial phenomena appear to us on earth, according to
Copernicus, is affected by both the motions of celestial bodies and
the motion of the earth, which is not a stationary body around which
everything else revolves. For Kant, analogously, the phenomena of
human experience depend on both the sensory data that we receive
passively through sensibility and the way our mind actively processes
this data according to its own a priori rules. These rules supply the
general framework in which the sensible world and all the objects (or
phenomena) in it appear to us. So the sensible world and its phenomena
are not entirely independent of the human mind, which contributes its
basic structure.



How does Kant's Copernican revolution in philosophy improve on
the strategy of the *Inaugural Dissertation* for reconciling
modern science with traditional morality and religion? First, it gives
Kant a new and ingenious way of placing modern science on an a priori
foundation. He is now in a position to argue that we can have a priori
knowledge about the basic laws of modern science because those laws
reflect the human mind's contribution to structuring our
experience. In other words, the sensible world necessarily conforms to
certain fundamental laws - such as that every event has a cause
- because the human mind constructs it according to those laws.
Moreover, we can identify those laws by reflecting on the conditions
of possible experience, which reveals that it would be impossible for
us to experience a world in which, for example, any given event fails
to have a cause. From this Kant concludes that metaphysics is indeed
possible in the sense that we can have a priori knowledge that the
entire sensible world - not just our actual experience, but any
possible human experience - necessarily conforms to certain
laws. Kant calls this immanent metaphysics or the metaphysics of
experience, because it deals with the essential principles that are
immanent to human experience.



But, second, if "we can cognize of things a priori only what we
ourselves have put into them," then we cannot have a priori
knowledge about things whose existence and nature are entirely
independent of the human mind, which Kant calls things in themselves
(Bxviii). In his words: "[F]rom this deduction of our faculty of
cognizing a priori [...] there emerges a very strange result
[...], namely that with this faculty we can never get beyond the
boundaries of possible experience, [...and] that such cognition
reaches appearances only, leaving the thing in itself as something
actual for itself but uncognized by us" (Bxix-xx). That
is, Kant's constructivist foundation for scientific knowledge
restricts science to the realm of appearances and implies that
transcendent metaphysics - i.e., a priori knowledge of things in
themselves that transcend possible human experience - is
impossible. In the *Critique* Kant thus rejects the insight
into an intelligible world that he defended in the *Inaugural
Dissertation*, and he now claims that rejecting knowledge about
things in themselves is necessary for reconciling science with
traditional morality and religion. This is because he claims that
belief in God, freedom, and immortality have a strictly moral basis,
and yet adopting these beliefs on moral grounds would be unjustified
if we could know that they were false. "Thus," Kant says,
"I had to deny knowledge in order to make room for faith"
(Bxxx). Restricting knowledge to appearances and relegating God and
the soul to an unknowable realm of things in themselves guarantees
that it is impossible to disprove claims about God and the freedom or
immortality of the soul, which moral arguments may therefore justify
us in believing. Moreover, the determinism of modern science no longer
threatens the freedom required by traditional morality, because
science and therefore determinism apply only to appearances, and there
is room for freedom in the realm of things in themselves, where the
self or soul is located. We cannot know (theoretically) that we are
free, because we cannot know anything about things in themselves. But
there are especially strong moral grounds for the belief in human
freedom, which acts as "the keystone" supporting other
morally grounded beliefs (5:3-4). In this way, Kant replaces
transcendent metaphysics with a new practical science that he calls
the metaphysics of morals. It thus turns out that two kinds of
metaphysics are possible: the metaphysics of experience (or nature)
and the metaphysics of morals, both of which depend on Kant's
Copernican revolution in philosophy.


## 3. Transcendental idealism



Perhaps the central and most controversial thesis of the *Critique
of Pure Reason* is that human beings experience only appearances,
not things in themselves; and that space and time are only subjective
forms of human intuition that would not subsist in themselves if one
were to abstract from all subjective conditions of human intuition.
Kant calls this thesis transcendental
 idealism.[7]
 One of his best summaries of it is arguably the following:



> 
> We have therefore wanted to say that all our intuition is nothing but
> the representation of appearance; that the things that we intuit are
> not in themselves what we intuit them to be, nor are their relations
> so constituted in themselves as they appear to us; and that if we
> remove our own subject or even only the subjective constitution of the
> senses in general, then all constitution, all relations of objects in
> space and time, indeed space and time themselves would disappear, and
> as appearances they cannot exist in themselves, but only in us. What
> may be the case with objects in themselves and abstracted from all
> this receptivity of our sensibility remains entirely unknown to us. We
> are acquainted with nothing except our way of perceiving them, which
> is peculiar to us, and which therefore does not necessarily pertain to
> every being, though to be sure it pertains to every human being. We
> are concerned solely with this. Space and time are its pure forms,
> sensation in general its matter. We can cognize only the former a
> priori, i.e., prior to all actual perception, and they are therefore
> called pure intuition; the latter, however, is that in our cognition
> that is responsible for its being called a posteriori cognition, i.e.,
> empirical intuition. The former adheres to our sensibility absolutely
> necessarily, whatever sort of sensations we may have; the latter can
> be very different.
>  (A42/B59-60)[8]
> 



Kant introduces transcendental idealism in the part of the
*Critique* called the Transcendental Aesthetic, and scholars
generally agree that for Kant transcendental idealism encompasses at
least the following claims:


* In some sense, human beings experience only appearances, not
things in themselves.
* Space and time are not things in themselves, or determinations of
things in themselves that would remain if one abstracted from all
subjective conditions of human intuition. [Kant labels this conclusion
a) at A26/B42 and again at A32-33/B49. It is at least a crucial
part of what he means by calling space and time transcendentally ideal
(A28/B44, A35-36/B52)].
* Space and time are nothing other than the subjective forms of
human sensible intuition. [Kant labels this conclusion b) at A26/B42
and again at A33/B49-50].
* Space and time are empirically real, which means that
"everything that can come before us externally as an
object" is in both space and time, and that our internal
intuitions of ourselves are in time (A28/B44,
A34-35/B51-51).



But scholars disagree widely on how to interpret these claims, and
there is no such thing as the standard interpretation of Kant's
transcendental idealism. Two general types of interpretation have been
especially influential, however. This section provides an overview of
these two interpretations, although it should be emphasized that much
important scholarship on transcendental idealism does not fall neatly
into either of these two camps.


### 3.1 The two-objects interpretation



The two-objects reading is the traditional interpretation of
Kant's transcendental idealism. It goes back to the earliest
review of the *Critique* - the so-called Gottingen
review by Christian Garve (1742-1798) and J. G. Feder
 (1740-1821)[9]
 - and it was the dominant way of interpreting Kant's
transcendental idealism during his own lifetime. It has been a live
interpretive option since then and remains so today, although it no
longer enjoys the dominance that it once
 did.[10]



According to the two-objects interpretation, transcendental idealism
is essentially a metaphysical thesis that distinguishes between two
classes of objects: appearances and things in themselves. Another name
for this view is the two-worlds interpretation, since it can also be
expressed by saying that transcendental idealism essentially
distinguishes between a world of appearances and another world of
things in themselves.



Things in themselves, on this interpretation, are absolutely real in
the sense that they would exist and have whatever properties they have
even if no human beings were around to perceive them. Appearances, on
the other hand, are not absolutely real in that sense, because their
existence and properties depend on human perceivers. Moreover,
whenever appearances do exist, in some sense they exist in the mind of
human perceivers. So appearances are mental entities or mental
representations. This, coupled with the claim that we experience only
appearances, makes transcendental idealism a form of phenomenalism on
this interpretation, because it reduces the objects of experience to
mental representations. All of our experiences - all of our
perceptions of objects and events in space, even those objects and
events themselves, and all non-spatial but still temporal thoughts and
feelings - fall into the class of appearances that exist in the
mind of human perceivers. These appearances cut us off entirely from
the reality of things in themselves, which are non-spatial and
non-temporal. Yet Kant's theory, on this interpretation,
nevertheless requires that things in themselves exist, because they
must transmit to us the sensory data from which we construct
appearances. In principle we cannot know how things in themselves
affect our senses, because our experience and knowledge is limited to
the world of appearances constructed by and in the mind. Things in
themselves are therefore a sort of theoretical posit, whose existence
and role are required by the theory but are not directly
verifiable.



The main problems with the two-objects interpretation are
philosophical. Most readers of Kant who have interpreted his
transcendental idealism in this way have been - often very
- critical of it, for reasons such as the following:



First, at best Kant is walking a fine line in claiming on the one hand
that we can have no knowledge about things in themselves, but on the
other hand that we know that things in themselves exist, that they
affect our senses, and that they are non-spatial and non-temporal. At
worst his theory depends on contradictory claims about what we can and
cannot know about things in themselves. This objection was
influentially articulated by Jacobi, when he complained that
"without that presupposition [of things in themselves] I could
not enter into the system, but with it I could not stay within
it" (Jacobi 1787, 336).



Second, even if that problem is surmounted, it has seemed to many that
Kant's theory, interpreted in this way, implies a radical form
of skepticism that traps each of us within the contents of our own
mind and cuts us off from reality. Some versions of this objection
proceed from premises that Kant rejects. One version maintains that
things in themselves are real while appearances are not, and hence
that on Kant's view we cannot have experience or knowledge of
reality. But Kant denies that appearances are unreal: they are just as
real as things in themselves but are in a different metaphysical
class. Another version claims that truth always involves a
correspondence between mental representations and things in
themselves, from which it would follow that on Kant's view it is
impossible for us to have true beliefs about the world. But just as
Kant denies that things in themselves are the only (or privileged)
reality, he also denies that correspondence with things in themselves
is the only kind of truth. Empirical judgments are true just in case
they correspond with their empirical objects in accordance with the a
priori principles that structure all possible human experience. But
the fact that Kant can appeal in this way to an objective criterion of
empirical truth that is internal to our experience has not been enough
to convince some critics that Kant is innocent of an unacceptable form
of skepticism, mainly because of his insistence on our irreparable
ignorance about things in themselves.



Third and finally, Kant's denial that things in themselves are
spatial or temporal has struck many of his readers as incoherent. The
role of things in themselves, on the two-object interpretation, is to
affect our senses and thereby to provide the sensory data from which
our cognitive faculties construct appearances within the framework of
our a priori intuitions of space and time and a priori concepts such
as causality. But if there is no space, time, change, or causation in
the realm of things in themselves, then how can things in themselves
affect us? Transcendental affection seems to involve a causal relation
between things in themselves and our sensibility. If this is simply
the way we unavoidably think about transcendental affection, because
we can give positive content to this thought only by employing the
concept of a cause, while it is nevertheless strictly false that
things in themselves affect us causally, then it seems not only that
we are ignorant of how things in themselves really affect us. It
seems, rather, to be incoherent that things in themselves could affect
us at all if they are not in space or time.


### 3.2 The two-aspects interpretation



The two-aspects reading attempts to interpret Kant's
transcendental idealism in a way that enables it to be defended
against at least some of these objections. On this view,
transcendental idealism does not distinguish between two classes of
objects but rather between two different aspects of one and the same
class of objects. For this reason it is also called the one-world
interpretation, since it holds that there is only one world in
Kant's ontology, and that at least some objects in that world
have two different aspects: one aspect that appears to us, and another
aspect that does not appear to us. That is, appearances are aspects of
the same objects that also exist in themselves. So, on this reading,
appearances are not mental representations, and transcendental
idealism is not a form of
 phenomenalism.[11]



There are at least two main versions of the two-aspects theory. One
version treats transcendental idealism as a metaphysical theory
according to which objects have two aspects in the sense that they
have two sets of properties: one set of relational properties that
appear to us and are spatial and temporal, and another set of
intrinsic properties that do not appear to us and are not spatial or
temporal (Langton 1998). This property-dualist interpretation faces
epistemological objections similar to those faced by the two-objects
interpretation, because we are in no better position to acquire
knowledge about properties that do not appear to us than we are to
acquire knowledge about objects that do not appear to us. Moreover,
this interpretation also seems to imply that things in themselves are
spatial and temporal, since appearances have spatial and temporal
properties, and on this view appearances are the same objects as
things in themselves. But Kant explicitly denies that space and time
are properties of things in themselves.



A second version of the two-aspects theory departs more radically from
the traditional two-objects interpretation by denying that
transcendental idealism is at bottom a metaphysical theory. Instead,
it interprets transcendental idealism as a fundamentally
epistemological theory that distinguishes between two standpoints on
the objects of experience: the human standpoint, from which objects
are viewed relative to epistemic conditions that are peculiar to human
cognitive faculties (namely, the a priori forms of our sensible
intuition); and the standpoint of an intuitive intellect, from which
the same objects could be known in themselves and independently of any
epistemic conditions (Allison 2004). Human beings cannot really take
up the latter standpoint but can form only an empty concept of things
as they exist in themselves by abstracting from all the content of our
experience and leaving only the purely formal thought of an object in
general. So transcendental idealism, on this interpretation, is
essentially the thesis that we are limited to the human standpoint,
and the concept of a thing in itself plays the role of enabling us to
chart the boundaries of the human standpoint by stepping beyond them
in abstract (but empty) thought.



One criticism of this epistemological version of the two-aspects
theory is that it avoids the objections to other interpretations by
attributing to Kant a more limited project than the text of the
*Critique* warrants. There are passages that support this
 reading.[12]
 But there are also many passages in both editions of the
*Critique* in which Kant describes appearances as
representations in the mind and in which his distinction between
appearances and things in themselves is given not only epistemological
but metaphysical
 significance.[13]
 It is unclear whether all of these texts admit of a single,
consistent interpretation. 


## 4. The transcendental deduction



The transcendental deduction is the central argument of the
*Critique of Pure Reason* and one of the most complex and
difficult texts in the history of philosophy. Given its complexity,
there are naturally many different ways of interpreting the
 deduction.[14]
 This brief overview provides one perspective on some of its main
ideas.



The transcendental deduction occurs in the part of the
*Critique* called the Analytic of Concepts, which deals with
the a priori concepts that, on Kant's view, our understanding
uses to construct experience together with the a priori forms of our
sensible intuition (space and time), which he discussed in the
Transcendental Aesthetic. Kant calls these a priori concepts
"categories," and he argues elsewhere (in the so-called
metaphysical deduction) that they include such concepts as substance
and cause. The goal of the transcendental deduction is to show that we
have a priori concepts or categories that are objectively valid, or
that apply necessarily to all objects in the world that we experience.
To show this, Kant argues that the categories are necessary conditions
of experience, or that we could not have experience without the
categories. In Kant's words:



> 
> [T]he objective validity of the categories, as a priori concepts,
> rests on the fact that through them alone is experience possible (as
> far as the form of thinking is concerned). For they then are related
> necessarily and a priori to objects of experience, since only by means
> of them can any object of experience be thought at all.
> 
> 
> The transcendental deduction of all a priori concepts therefore has a
> principle toward which the entire investigation must be directed,
> namely this: that they must be recognized as a priori conditions of
> the possibility of experiences (whether of the intuition that is
> encountered in them, or of the thinking). Concepts that supply the
> objective ground of the possibility of experience are necessary just
> for that reason. (A93-94/B126)
> 
> 
> 



The strategy Kant employs to argue that the categories are conditions
of experience is the main source of both the obscurity and the
ingenuity of the transcendental deduction. His strategy is to argue
that the categories are necessary specifically for self-consciousness,
for which Kant often uses the Leibnizian term
"apperception."


### 4.1 Self-consciousness



One way to approach Kant's argument is to contrast his view of
self-consciousness with two alternative views that he rejects. Each of
these views, both Kant's and those he rejects, can be seen as
offering competing answers the question: what is the source of our
sense of an ongoing and invariable self that persists throughout all
the changes in our experience?



The first answer to this question that Kant rejects is that
self-consciousness arises from some particular content being present
in each of one's representations. This material conception of
self-consciousness, as we may call it, is suggested by Locke's
account of personal identity. According to Locke, "it being the
same consciousness that makes a Man be himself to himself, personal
Identity depends on that only, whether it be annexed only to one
individual Substance, or can be continued in a succession of several
Substances" (*Essay* 2.27.10). What Locke calls
"the same consciousness" may be understood as some
representational content that is always present in my experience and
that both identifies any experience as mine and gives me a sense of a
continuous self by virtue of its continual presence in my experience.
One problem with this view, Kant believes, is that there is no such
representational content that is invariably present in experience, so
the sense of an ongoing self cannot possibly arise from that
non-existent content (what Locke calls "consciousness")
being present in each of one's representations. In Kant's
words, self-consciousness "does not yet come about by my
accompanying each representation with consciousness, but rather by my
adding one representation to the other and being conscious of their
synthesis. Therefore it is only because I can combine a manifold of
given representations in one consciousness that it is possible for me
to represent the identity of the consciousness in these
representations" (B133). Here Kant claims, against the Lockean
view, that self-consciousness arises from combining (or synthesizing)
representations with one another regardless of their content. In
short, Kant has a formal conception of self-consciousness rather than
a material one. Since no particular content of my experience is
invariable, self-consciousness must derive from my experience having
an invariable form or structure, and consciousness of the identity of
myself through all of my changing experiences must consist in
awareness of the formal unity and law-governed regularity of my
experience. The continuous form of my experience is the necessary
correlate for my sense of a continuous self.



There are at least two possible versions of the formal conception of
self-consciousness: a realist and an idealist version. On the realist
version, nature itself is law-governed and we become self-conscious by
attending to its law-governed regularities, which also makes this an
empiricist view of self-consciousness. The idea of an identical self
that persists throughout all of our experience, on this view, arises
from the law-governed regularity of nature, and our representations
exhibit order and regularity because reality itself is ordered and
regular. Kant rejects this realist view and embraces a conception of
self-consciousness that is both formal and idealist. According to
Kant, the formal structure of our experience, its unity and
law-governed regularity, is an achievement of our cognitive faculties
rather than a property of reality in itself. Our experience has a
constant form because our mind constructs experience in a law-governed
way. So self-consciousness, for Kant, consists in awareness of the
mind's law-governed activity of synthesizing or combining
sensible data to construct a unified experience. As he expresses it,
"this unity of consciousness would be impossible if in the
cognition of the manifold the mind could not become conscious of the
identity of the function by means of which this manifold is
synthetically combined into one cognition" (A108).



Kant argues for this formal idealist conception of self-consciousness,
and against the formal realist view, on the grounds that "we can
represent nothing as combined in the object without having previously
combined it ourselves" (B130). In other words, even if reality
in itself were law-governed, its laws could not simply migrate over to
our mind or imprint themselves on us while our mind is entirely
passive. We must exercise an active capacity to represent the world as
combined or ordered in a law-governed way, because otherwise we could
not represent the world as law-governed even if it were law-governed
in itself. Moreover, this capacity to represent the world as
law-governed must be a priori because it is a condition of
self-consciousness, and we would already have to be self-conscious in
order to learn from our experience that there are law-governed
regularities in the world. So it is necessary for self-consciousness
that we exercise an a priori capacity to represent the world as
law-governed. But this would also be sufficient for self-consciousness
if we could exercise our a priori capacity to represent the world as
law-governed even if reality in itself were not law-governed. In that
case, the realist and empiricist conception of self-consciousness
would be false, and the formal idealist view would be true.



Kant's confidence that no empiricist account could possibly
explain self-consciousness may be based on his assumption that the
sense of self each of us has, the thought of oneself as identical
throughout all of one's changing experiences, involves necessity
and universality, which on his view are the hallmarks of the a priori.
This assumption is reflected in what we may call Kant's
principle of apperception: "The **I think** must **be
able** to accompany all my representations; for otherwise something
would be represented in me that could not be thought at all, which is
as much as to say that the representation would either be impossible
or else at least would be nothing for me"
 (B131-132).[15]
 Notice the claims about necessity and universality embodied in the
words "must" and "all" here. Kant is saying
that for a representation to count as mine, it must necessarily be
accessible to conscious awareness in some (perhaps indirect) way: I
must be able to accompany it with "I think...." All
of my representations must be accessible to consciousness in this way
(but they need not actually be conscious), because again that is
simply what makes a representation count as mine. Self-consciousness
for Kant therefore involves a priori knowledge about the necessary and
universal truth expressed in this principle of apperception, and a
priori knowledge cannot be based on experience.



Kant may have developed this thread of his argument in the
transcendental deduction after reading Johann Nicolaus Tetens
(1736-1807) rather than through a direct encounter with
Locke's texts (Tetens 1777, Kitcher 2011). On the subject of
self-consciousness, Tetens was a follower of Locke and also engaged
with Hume's arguments for rejecting a continuing self. So
Kant's actual opponents in the deduction may have been Lockean
and Humean positions as represented by Tetens, as well as rationalist
views that Kant would have encountered directly in texts by Leibniz,
Wolff, and some of their followers.


### 4.2 Objectivity and judgment



On the basis of this formal idealist conception of self-consciousness,
Kant's argument (at least one central thread of it) moves
through two more conditions of self-consciousness in order to
establish the objective validity of the categories. The next condition
is that self-consciousness requires me to represent an objective world
distinct from my subjective representations - that is, distinct
from my thoughts about and sensations of that objective world. Kant
uses this connection between self-consciousness and objectivity to
insert the categories into his argument.



In order to be self-conscious, I cannot be wholly absorbed in the
contents of my perceptions but must distinguish myself from the rest
of the world. But if self-consciousness is an achievement of the mind,
then how does the mind achieve this sense that there is a distinction
between the I that perceives and the contents of its perceptions?
According to Kant, the mind achieves this sense by distinguishing
representations that necessarily belong together from representations
that are not necessarily connected but are merely associated in a
contingent way. Consider Kant's example of the perception of a
house (B162). Imagine a house that is too large to fit into your
visual field from your vantage point near its front door. Now imagine
that you walk around the house, successively perceiving each of its
sides. Eventually you perceive the entire house, but not all at once,
and you judge that each of your representations of the sides of the
house necessarily belong together (as sides of one house) and that
anyone who denied this would be mistaken. But now imagine that you
grew up in this house and associate a feeling of nostalgia with it.
You would not judge that representations of this house are necessarily
connected with feelings of nostalgia. That is, you would not think
that other people seeing the house for the first time would be
mistaken if they denied that it is connected with nostalgia, because
you recognize that this house is connected with nostalgia for you but
not necessarily for everyone. Yet you distinguish this merely
subjective connection from the objective connection between sides of
the house, which is objective because the sides of the house
necessarily belong together "in the object," because this
connection holds for everyone universally, and because it is possible
to be mistaken about it. The point here is not that we must
successfully identify which representations necessarily belong
together and which are merely associated contingently, but rather that
to be self-conscious we must at least make this general distinction
between objective and merely subjective connections of
representations.



At this point (at least in the second edition text) Kant introduces
the key claim that judgment is what enables us to distinguish
objective connections of representations that necessarily belong
together from merely subjective and contingent associations:
"[A] judgment is nothing other than the way to bring given
cognitions to the objective unity of apperception. That is the aim of
the copula **is** in them: to distinguish the objective unity of
given representations from the subjective. For this word designates
the relation of the representations to the original apperception and
its necessary unity" (B141-142). Kant is speaking here
about the mental act of judging that results in the formation of a
judgment. Judging is an act of what Kant calls synthesis, which he
defines as "the action of putting different representations
together with each other and comprehending their manifoldness in one
cognition" (A77/B103). In other words, to synthesize is in
general to combine several representations into a single (more)
complex representation, and to judge is specifically to combine
concepts into a judgment - that is, to join a subject concept to
a predicate concept by means of the copula, as in "the body is
heavy" or "the house is four-sided." Judgments need
not be true, of course, but they always have a truth value (true or
false) because they make claims to objective validity. When I say, by
contrast, that "If I carry a body, I feel a pressure of
weight," or that "if I see this house, I feel
nostalgia," I am not making a judgment about the object (the
body or the house) but rather I am expressing a subjective association
that may apply only to me
 (B142).[16]



Kant's reference to the necessary unity of apperception or
self-consciousness in the quotation above means (at least) that the
action of judging is the way our mind achieves self-consciousness. We
must represent an objective world in order to distinguish ourselves
from it, and we represent an objective world by judging that some
representations necessarily belong together. Moreover, recall from
 4.1
 that, for Kant, we must have an a priori capacity to represent the
world as law-governed, because "we can represent nothing as
combined (or connected) in the object without having previously
combined it ourselves" (B130). It follows that objective
connections in the world cannot simply imprint themselves on our mind.
Rather, experience of an objective world must be constructed by
exercising an a priori capacity to judge, which Kant calls the faculty
of understanding (A80-81/B106). The understanding constructs
experience by providing the a priori rules, or the framework of
necessary laws, in accordance with which we judge representations to
be objective. These rules are the pure concepts of the understanding
or categories, which are therefore conditions of self-consciousness,
since they are rules for judging about an objective world, and
self-consciousness requires that we distinguish ourselves from an
objective world.



Kant identifies the categories in what he calls the metaphysical
deduction, which precedes the transcendental
 deduction.[17]
 Very briefly, since the categories are a priori rules for judging,
Kant argues that an exhaustive table of categories can be derived from
a table of the basic logical forms of judgments. For example,
according to Kant the logical form of the judgment that "the
body is heavy" would be singular, affirmative, categorical, and
assertoric. But since categories are not mere logical functions but
instead are rules for making judgments about objects or an objective
world, Kant arrives at his table of categories by considering how each
logical function would structure judgments about objects (within our
spatio-temporal forms of intuition). For example, he claims that
categorical judgments express a logical relation between subject and
predicate that corresponds to the ontological relation between
substance and accident; and the logical form of a hypothetical
judgment expresses a relation that corresponds to cause and effect.
Taken together with this argument, then, the transcendental deduction
argues that we become self-conscious by representing an objective
world of substances that interact according to causal laws.


### 4.3 The law-giver of nature



The final condition of self-consciousness that Kant adds to the
preceding conditions is that our understanding must cooperate with
sensibility to construct one, unbounded, and unified space-time to
which all of our representations may be related. 



To see why this further condition is required, consider that so far we
have seen why Kant holds that we must represent an objective world in
order to be self-conscious, but we could represent an objective world
even if it were not possible to relate all of our representations to
this objective world. For all that has been said so far, we might
still have unruly representations that we cannot relate in any way to
the objective framework of our experience. On Kant's view, this
would be a problem because, as we have seen, he holds that
self-consciousness involves universality and necessity: according to
his principle of apperception, "the **I think** must **be
able** to accompany all my representations" (B131). Yet if, on
the one hand, I had representations that I could not relate in some
way to an objective world, then I could not accompany those
representations with "I think" or recognize them as my
representations, because I can say "I think..." about
any given representation only by relating it to an objective world,
according to the argument just discussed. So I must be able to relate
any given representation to an objective world in order for it to
count as mine. On the other hand, self-consciousness would also be
impossible if I represented multiple objective worlds, even if I could
relate all of my representations to some objective world or other. In
that case, I could not become conscious of an identical self that has,
say, representation 1 in space-time A and representation 2 in
space-time B. It may be possible to imagine disjointed spaces and
times, but it is not possible to represent them as objectively real.
So self-consciousness requires that I can relate all of my
representations to a single objective world.



The reason why I must represent this one objective world by means of a
unified and unbounded space-time is that, as Kant argued in the
Transcendental Aesthetic, space and time are the pure forms of human
intuition. If we had different forms of intuition, then our experience
would still have to constitute a unified whole in order for us to be
self-conscious, but this would not be a spatio-temporal whole. Given
that space and time are our forms of intuition, however, our
understanding must still cooperate with sensibility to construct a
spatio-temporal whole of experience because, once again, "we can
represent nothing as combined in the object without having previously
combined it ourselves," and "all combination [...] is
an action of the understanding" (B130). So Kant distinguishes
between space and time as pure forms of intuition, which belong solely
to sensibility; and the formal intuitions of space and time (or
space-time), which are unified by the understanding (B160-161).
These formal intuitions are the spatio-temporal whole within which our
understanding constructs experience in accordance with the
 categories.[18]



The most important implication of Kant's claim that the
understanding constructs a single whole of experience to which all of
our representations can be related is that, since he defines nature
"regarded materially" as "the sum total of all
appearances" and he has argued that the categories are
objectively valid of all possible appearances, on his view it follows
that our categories are the source of the fundamental laws of nature
"regarded formally" (B163, 165). So Kant concludes on this
basis that the understanding is the true law-giver of nature. In his
words: "all appearances in nature, as far as their combination
is concerned, stand under the categories, on which nature (considered
merely as nature in general) depends, as the original ground of its
necessary lawfulness (as nature regarded formally)" (B165). Or
more strongly: "we ourselves bring into the appearances that
order and regularity that we call **nature**, and moreover we would
not be able to find it there if we, or the nature of our mind, had not
originally put it there. [...] The understanding is thus not
merely a faculty for making rules through the comparison of the
appearances: it is itself the legislation for nature, i.e., without
understanding there would not be any nature at all"
(A125-126). 


## 5. Morality and freedom



Having examined two central parts of Kant's positive project in
theoretical philosophy from the *Critique of Pure Reason*,
transcendental idealism and the transcendental deduction, let us now
turn to his practical philosophy in the *Critique of Practical
Reason*. Since Kant's philosophy is deeply systematic, this
section begins with a preliminary look at how his theoretical and
practical philosophy fit together (see also section
 7).


### 5.1 Theoretical and practical autonomy



The fundamental idea of Kant's philosophy is human autonomy. So
far we have seen this in Kant's constructivist view of
experience, according to which our understanding is the source of the
general laws of nature. "Autonomy" literally means giving
the law to oneself, and on Kant's view our understanding
provides laws that constitute the a priori framework of our
experience. Our understanding does not provide the matter or content
of our experience, but it does provide the basic formal structure
within which we experience any matter received through our senses.
Kant's central argument for this view is the transcendental
deduction, according to which it is a condition of self-consciousness
that our understanding constructs experience in this way. So we may
call self-consciousness the highest principle of Kant's
theoretical philosophy, since it is (at least) the basis for all of
our a priori knowledge about the structure of nature.



Kant's moral philosophy is also based on the idea of autonomy.
He holds that there is a single fundamental principle of morality, on
which all specific moral duties are based. He calls this moral law (as
it is manifested to us) the categorical imperative (see
 5.4).
 The moral law is a product of reason, for Kant, while the basic laws
of nature are products of our understanding. There are important
differences between the senses in which we are autonomous in
constructing our experience and in morality. For example, Kant regards
understanding and reason as different cognitive faculties, although he
sometimes uses "reason" in a wide sense to cover
 both.[19]
 The categories and therefore the laws of nature are dependent on our
specifically human forms of intuition, while reason is not. The moral
law does not depend on any qualities that are peculiar to human nature
but only on the nature of reason as such, although its manifestation
to us as a categorical imperative (as a law of duty) reflects the fact
that the human will is not necessarily determined by pure reason but
is also influenced by other incentives rooted in our needs and
inclinations; and our specific duties deriving from the categorical
imperative do reflect human nature and the contingencies of human
life. Despite these differences, however, Kant holds that we give the
moral law to ourselves, as we also give the general laws of nature to
ourselves, though in a different sense. Moreover, we each necessarily
give the same moral law to ourselves, just as we each construct our
experience in accordance with the same categories. To summarize:


* Theoretical philosophy is about how the world is (A633/B661). Its
highest principle is self-consciousness, on which our knowledge of the
basic laws of nature is based. Given sensory data, our understanding
constructs experience according to these a priori laws.
* Practical philosophy is about how the world ought to be (ibid.,
A800-801/B828-829). Its highest principle is the moral
law, from which we derive duties that command how we ought to act in
specific situations. Kant also claims that reflection on our moral
duties and our need for happiness leads to the thought of an ideal
world, which he calls the highest good (see section
 6).
 Given how the world is (theoretical philosophy) and how it ought to
be (practical philosophy), we aim to make the world better by
constructing or realizing the highest good.



So both parts of Kant's philosophy are about autonomously
constructing a world, but in different senses. In theoretical
philosophy, we use our categories and forms of intuition to construct
a world of experience or nature. In practical philosophy, we use the
moral law to construct the idea of a moral world or a realm of ends
that guides our conduct (4:433), and ultimately to transform the
natural world into the highest good. Finally, transcendental idealism
is the framework within which these two parts of Kant's
philosophy fit together (20:311). Theoretical philosophy deals with
appearances, to which our knowledge is strictly limited; and practical
philosophy deals with things in themselves, although it does not give
us knowledge about things in themselves but only provides rational
justification for certain beliefs about them for practical
purposes.



To understand Kant's arguments that practical philosophy
justifies certain beliefs about things in themselves, it is necessary
to see them in the context of his criticism of German rationalist
metaphysics. The three traditional topics of Leibniz-Wolffian special
metaphysics were rational psychology, rational cosmology, and rational
theology, which dealt, respectively, with the human soul, the
world-whole, and God. In the part of the Critique of Pure Reason
called the Transcendental Dialectic, Kant argues against the
Leibniz-Wolffian view that human beings are capable of a priori
knowledge in each of these domains, and he claims that the errors of
Leibniz-Wolffian metaphysics are due to an illusion that has its seat
in the nature of human reason itself. According to Kant, human reason
necessarily produces ideas of the soul, the world-whole, and God; and
these ideas unavoidably produce the illusion that we have a priori
knowledge about transcendent objects corresponding to them. This is an
illusion, however, because in fact we are not capable of a priori
knowledge about any such transcendent objects. Nevertheless, Kant
attempts to show that these illusory ideas have a positive, practical
use. He thus reframes Leibniz-Wolffian special metaphysics as a
practical science that he calls the metaphysics of morals. On
Kant's view, our ideas of the soul, the world-whole, and God
provide the content of morally justified beliefs about human
immortality, human freedom, and the existence of God, respectively;
but they are not proper objects of speculative
 knowledge.[20]


### 5.2 Freedom



The most important belief about things in themselves that Kant thinks
only practical philosophy can justify concerns human freedom. Freedom
is important because, on Kant's view, moral appraisal
presupposes that we are free in the sense that we have the ability to
do otherwise. To see why, consider Kant's example of a man who
commits a theft (5:95ff.). Kant holds that in order for this
man's action to be morally wrong, it must have been within his
control in the sense that it was within his power at the time not to
have committed the theft. If this was not within his control at the
time, then, while it may be useful to punish him in order to shape his
behavior or to influence others, it nevertheless would not be correct
to say that his action was morally wrong. Moral rightness and
wrongness apply only to free agents who control their actions and have
it in their power, at the time of their actions, either to act rightly
or not. According to Kant, this is just common sense.



On these grounds, Kant rejects a type of compatibilism that he calls
the "comparative concept of freedom" and associates with
Leibniz (5:96-97). (Note that Kant has a specific type of
compatibilism in mind, which I will refer to simply as
"compatibilism," although there may be other types of
compatibilism that do not fit Kant's characterization of that
view). On the compatibilist view, as Kant understands it, I am free
whenever the cause of my action is within me. So I am unfree only when
something external to me pushes or moves me, but I am free whenever
the proximate cause of my body's movement is internal to me as
an "acting being" (5:96). If we distinguish between
involuntary convulsions and voluntary bodily movements, then on this
view free actions are just voluntary bodily movements. Kant ridicules
this view as a "wretched subterfuge" that tries to solve
an ancient philosophical problem "with a little quibbling about
words" (ibid.). This view, he says, assimilates human freedom to
"the freedom of a turnspit," or a projectile in flight, or
the motion of a clock's hands (5:96-97). The proximate
causes of these movements are internal to the turnspit, the
projectile, and the clock at the time of the movement. This cannot be
sufficient for moral responsibility.



Why not? The reason, Kant says, is ultimately that the causes of these
movements occur in time. Return to the theft example. A compatibilist
would say that the thief's action is free because its proximate
cause is inside him, and because the theft was not an involuntary
convulsion but a voluntary action. The thief decided to commit the
theft, and his action flowed from this decision. According to Kant,
however, if the thief's decision is a natural phenomenon that
occurs in time, then it must be the effect of some cause that occurred
in a previous time. This is an essential part of Kant's
Newtonian worldview and is grounded in the a priori laws
(specifically, the category of cause and effect) in accordance with
which our understanding constructs experience: every event has a cause
that begins in an earlier time. If that cause too was an event
occurring in time, then it must also have a cause beginning in a still
earlier time, etc. All natural events occur in time and are thoroughly
determined by causal chains that stretch backwards into the distant
past. So there is no room for freedom in nature, which is
deterministic in a strong sense.



The root of the problem, for Kant, is time. Again, if the
thief's choice to commit the theft is a natural event in time,
then it is the effect of a causal chain extending into the distant
past. But the past is out of his control now, in the present. Once the
past is past, he can't change it. On Kant's view, that is
why his actions would not be in his control in the present if they are
determined by events in the past. Even if he could control those past
events in the past, he cannot control them now. But in fact past
events were not in his control in the past either if they too were
determined by events in the more distant past, because eventually the
causal antecedents of his action stretch back before his birth, and
obviously events that occurred before his birth were never in his
control. So if the thief's choice to commit the theft is a
natural event in time, then it is not now and never was in his
control, and he could not have done otherwise than to commit the
theft. In that case, it would be a mistake to hold him morally
responsible for it.



Compatibilism, as Kant understands it, therefore locates the issue in
the wrong place. Even if the cause of my action is internal to me, if
it is in the past - for example, if my action today is
determined by a decision I made yesterday, or from the character I
developed in childhood - then it is not within my control now.
The real issue is not whether the cause of my action is internal or
external to me, but whether it is in my control now. For Kant,
however, the cause of my action can be within my control now only if
it is not in time. This is why Kant thinks that transcendental
idealism is the only way to make sense of the kind of freedom that
morality requires. Transcendental idealism allows that the cause of my
action may be a thing in itself outside of time: namely, my noumenal
self, which is free because it is not part of nature. No matter what
kind of character I have developed or what external influences act on
me, on Kant's view all of my intentional, voluntary actions are
immediate effects of my noumenal self, which is causally undetermined
(5:97-98). My noumenal self is an uncaused cause outside of
time, which therefore is not subject to the deterministic laws of
nature in accordance with which our understanding constructs
experience.



Many puzzles arise on this picture that Kant does not resolve. For
example, if my understanding constructs all appearances in my
experience of nature, not only appearances of my own actions, then why
am I responsible only for my own actions but not for everything that
happens in the natural world? Moreover, if I am not alone in the world
but there are many noumenal selves acting freely and incorporating
their free actions into the experience they construct, then how do
multiple transcendentally free agents interact? How do you integrate
my free actions into the experience that your understanding
 constructs?[21]
 In spite of these unsolved puzzles, Kant holds that we can make sense
of moral appraisal and responsibility only by thinking about human
freedom in this way, because it is the only way to prevent natural
necessity from undermining both.



Finally, since Kant invokes transcendental idealism to make sense of
freedom, interpreting his thinking about freedom leads us back to
disputes between the two-objects and two-aspects interpretations of
transcendental idealism. On the face of it, the two-objects
interpretation seems to make better sense of Kant's view of
transcendental freedom than the two-aspects interpretation. If
morality requires that I am transcendentally free, then it seems that
my true self, and not just an aspect of my self, must be outside of
time, according to Kant's argument. But applying the two-objects
interpretation to freedom raises problems of its own, since it
involves making a distinction between noumenal and phenomenal selves
that does not arise on the two-aspects view. If only my noumenal self
is free, and freedom is required for moral responsibility, then my
phenomenal self is not morally responsible. But how are my noumenal
and phenomenal selves related, and why is punishment inflicted on
phenomenal selves? It is unclear whether and to what extent appealing
to Kant's theory of freedom can help to settle disputes about
the proper interpretation of transcendental idealism, since there are
serious questions about the coherence of Kant's theory on either
interpretation.


### 5.3 The fact of reason



Can we know that we are free in this transcendental sense?
Kant's response is tricky. On the one hand, he distinguishes
between theoretical knowledge and morally justified belief
(A820-831/B848-859). We do not have theoretical knowledge
that we are free or about anything beyond the limits of possible
experience, but we are morally justified in believing that we are free
in this sense. On the other hand, Kant also uses stronger language
than this when discussing freedom. For example, he says that
"among all the ideas of speculative reason freedom is the only
one the possibility of which we know a priori, though without having
any insight into it, because it is the condition of the moral law,
which we do know." In a footnote to this passage, Kant explains
that we know freedom a priori because "were there no freedom,
the moral law would not be encountered at all in ourselves," and
on Kant's view everyone does encounter the moral law a priori
(5:4). For this reason, Kant claims that the moral law
"proves" the objective, "though only practical,
undoubted reality" of freedom (5:48-49). So Kant wants to
say that we do have knowledge of the reality of freedom, but that this
is practical knowledge of a practical reality, or cognition
"only for practical purposes," by which he means to
distinguish it from theoretical knowledge based on experience or
reflection on the conditions of experience (5:133). Our practical
knowledge of freedom is based instead on the moral law. The difference
between Kant's stronger and weaker language seems mainly to be
that his stronger language emphasizes that our belief or practical
knowledge about freedom is unshakeable and that it in turn provides
support for other morally grounded beliefs in God and the immortality
of the soul. 



Kant calls our consciousness of the moral law, our awareness that the
moral law binds us or has authority over us, the "fact of
reason" (5:31-32, 42-43, 47, 55). So, on his view,
the fact of reason is the practical basis for our belief or practical
knowledge that we are free. Kant insists that this moral consciousness
is "undeniable," "a priori," and
"unavoidable" (5:32, 47, 55). Every human being has a
conscience, a common sense grasp of morality, and a firm conviction
that he or she is morally accountable. We may have different beliefs
about the source of morality's authority - God, social
convention, human reason. We may arrive at different conclusions about
what morality requires in specific situations. And we may violate our
own sense of duty. But we all have a conscience, and an unshakeable
belief that morality applies to us. According to Kant, this belief
cannot and does not need to be justified or "proved by any
deduction" (5:47). It is just a ground-level fact about human
beings that we hold ourselves morally accountable. But Kant is making
a normative claim here as well: it is also a fact, which cannot and
does not need to be justified, that we are morally accountable, that
morality does have authority over us. Kant holds that philosophy
should be in the business of defending this common sense moral belief,
and that in any case we could never prove or disprove it (4:459).



Kant may hold that the fact of reason, or our consciousness of moral
obligation, implies that we are free on the grounds that ought implies
can. In other words, Kant may believe that it follows from the fact
that we ought (morally) to do something that we can or are able to do
it. This is suggested, for example, by a passage in which Kant asks us
to imagine someone threatened by his prince with immediate execution
unless he "give[s] false testimony against an honorable man whom
the prince would like to destroy under a plausible pretext."
Kant says that "[h]e would perhaps not venture to assert whether
he would do it or not, but he must admit without hesitation that it
would be possible for him. He judges, therefore, that he can do
something because he is aware that he ought to do it and cognizes
freedom within him, which, without the moral law, would have remained
unknown to him" (5:30). This is a hypothetical example of an
action not yet carried out. It seems that pangs of guilt about the
immorality of an action that you carried out in the past, on this
reasoning, would imply more directly that you have (or at least had)
the ability to act otherwise than you did, and therefore that you are
free in Kant's sense.


### 5.4 The categorical imperative



In both the *Groundwork of the Metaphysics of Morals* and the
*Critique of Practical Reason*, Kant also gives a more detailed
argument for the conclusion that morality and freedom reciprocally
imply one another, which is sometimes called the reciprocity thesis
(Allison 1990). On this view, to act morally is to exercise freedom,
and the only way to fully exercise freedom is to act morally.
Kant's arguments for this view differ in these texts, but the
general structure of his argument in the *Critique of Practical
Reason* may be summarized as follows.



First, it follows from the basic idea of having a will that to act at
all is to act on some principle, or what Kant calls a maxim. A maxim
is a subjective rule or policy of action: it says what you are doing
and why. Kant gives as examples the maxims "to let no insult
pass unavenged" and "to increase my wealth by every safe
means" (5:19, 27). We may be unaware of our maxims, we may not
act consistently on the same maxims, and our maxims may not be
consistent with one another. But Kant holds that since we are rational
beings our actions always aim at some sort of end or goal, which our
maxim expresses. The goal of an action may be something as basic as
gratifying a desire, or it may be something more complex such as
becoming a doctor or a lawyer. In any case, the causes of our actions
are never our desires or impulses, on Kant's view. If I act to
gratify some desire, then I choose to act on a maxim that specifies
the gratification of that desire as the goal of my action. For
example, if I desire some coffee, then I may act on the maxim to go to
a cafe and buy some coffee in order to gratify that desire.



Second, Kant distinguishes between two basic kinds of principles or
rules that we can act on: what he calls material and formal
principles. To act in order to satisfy some desire, as when I act on
the maxim to go for coffee at a cafe, is to act on a material
principle (5:21ff.). Here the desire (for coffee) fixes the goal,
which Kant calls the object or matter of the action, and the principle
says how to achieve that goal (go to a cafe). Corresponding to
material principles, on Kant's view, are what he calls
hypothetical imperatives. A hypothetical imperative is a principle of
rationality that says I should act in a certain way if I choose to
satisfy some desire. If maxims in general are rules that describe how
one does act, then imperatives in general prescribe how one should
act. An imperative is hypothetical if it says how I should act only if
I choose to pursue some goal in order to gratify a desire (5:20).
This, for example, is a hypothetical imperative: if you want coffee,
then go to the cafe. This hypothetical imperative applies to you only
if you desire coffee and choose to gratify that desire.



In contrast to material principles, formal principles describe how one
acts without making reference to any desires. This is easiest to
understand through the corresponding kind of imperative, which Kant
calls a categorical imperative. A categorical imperative commands
unconditionally that I should act in some way. So while hypothetical
imperatives apply to me only on the condition that I have and set the
goal of satisfying the desires that they tell me how to satisfy,
categorical imperatives apply to me no matter what my goals and
desires may be. Kant regards moral laws as categorical imperatives,
which apply to everyone unconditionally. For example, the moral
requirement to help others in need does not apply to me only if I
desire to help others in need, and the duty not to steal is not
suspended if I have some desire that I could satisfy by stealing.
Moral laws do not have such conditions but rather apply
unconditionally. That is why they apply to everyone in the same
way.



Third, insofar as I act only on material principles or hypothetical
imperatives, I do not act freely, but rather I act only to satisfy
some desire(s) that I have, and what I desire is not ultimately within
my control. To some limited extent we are capable of rationally
shaping our desires, but insofar as we choose to act in order to
satisfy desires we are choosing to let nature govern us rather than
governing ourselves (5:118). We are always free in the sense that we
always have the capacity to govern ourselves rationally instead of
letting our desires set our ends for us. But we may (freely) fail to
exercise that capacity. Moreover, since Kant holds that desires never
cause us to act, but rather we always choose to act on a maxim even
when that maxim specifies the satisfaction of a desire as the goal of
our action, it also follows that we are always free in the sense that
we freely choose our maxims. Nevertheless, our actions are not free in
the sense of being autonomous if we choose to act only on material
principles, because in that case we do not give the law to ourselves,
but instead we choose to allow nature in us (our desires) to determine
the law for our actions. 



Finally, the only way to act freely in the full sense of exercising
autonomy is therefore to act on formal principles or categorical
imperatives, which is also to act morally. Kant does not mean that
acting autonomously requires that we take no account of our desires,
which would be impossible (5:25, 61). Rather, he holds that we
typically formulate maxims with a view to satisfying our desires, but
that "as soon as we draw up maxims of the will for
ourselves" we become immediately conscious of the moral law
(5:29). This immediate consciousness of the moral law takes the
following form:



> 
> I have, for example, made it my maxim to increase my wealth by every
> safe means. Now I have a deposit in my hands, the owner of which has
> died and left no record of it. This is, naturally, a case for my
> maxim. Now I want only to know whether that maxim could also hold as a
> universal practical law. I therefore apply the maxim to the present
> case and ask whether it could indeed take the form of a law, and
> consequently whether I could through my maxim at the same time give
> such a law as this: that everyone may deny a deposit which no one can
> prove has been made. I at once become aware that such a principle, as
> a law, would annihilate itself since it would bring it about that
> there would be no deposits at all. (5:27)
> 



In other words, to assess the moral permissibility of my maxim, I ask
whether everyone could act on it, or whether it could be willed as a
universal law. The issue is not whether it would be good if everyone
acted on my maxim, or whether I would like it, but only whether it
would be possible for my maxim to be willed as a universal law. This
gets at the form, not the matter or content, of the maxim. A maxim has
morally permissible form, for Kant, only if it could be willed as a
universal law. If my maxim fails this test, as this one does, then it
is morally impermissible for me to act on it.



If my maxim passes the universal law test, then it is morally
permissible for me to act on it, but I fully exercise my autonomy only
if my fundamental reason for acting on this maxim is that it is
morally permissible or required that I do so. Imagine that I am moved
by a feeling of sympathy to formulate the maxim to help someone in
need. In this case, my original reason for formulating this maxim is
that a certain feeling moved me. Such feelings are not entirely within
my control and may not be present when someone actually needs my help.
But this maxim passes Kant's test: it could be willed as a
universal law that everyone help others in need from motives of
sympathy. So it would not be wrong to act on this maxim when the
feeling of sympathy so moves me. But helping others in need would not
fully exercise my autonomy unless my fundamental reason for doing so
is not that I have some feeling or desire, but rather that it would be
right or at least permissible to do so. Only when such a purely formal
principle supplies the fundamental motive for my action do I act
autonomously.



So the moral law is a law of autonomy in the sense that "freedom
and unconditional practical law reciprocally imply each another"
(5:29). Even when my maxims are originally suggested by my feelings
and desires, if I act only on morally permissible (or required) maxims
because they are morally permissible (or required), then my actions
will be autonomous. And the reverse is true as well: for Kant this is
the only way to act
 autonomously.[22]


## 6. The highest good and practical postulates



Kant holds that reason unavoidably produces not only consciousness of
the moral law but also the idea of a world in which there is both
complete virtue and complete happiness, which he calls the highest
good. Our duty to promote the highest good, on Kant's view, is
the sum of all moral duties, and we can fulfill this duty only if we
believe that the highest good is a possible state of affairs.
Furthermore, we can believe that the highest good is possible only if
we also believe in the immortality of the soul and the existence of
God, according to Kant. On this basis, he claims that it is morally
necessary to believe in the immortality of the soul and the existence
of God, which he calls postulates of pure practical reason. This
section briefly outlines Kant's view of the highest good and his
argument for these practical postulates in the *Critique of
Practical Reason* and other works.


### 6.1 The highest good



In the previous section we saw that, on Kant's view, the moral
law is a purely formal principle that commands us to act only on
maxims that have what he calls lawgiving form, which maxims have only
if they can be willed as universal laws. Moreover, our fundamental
reason for choosing to act on such maxims should be that they have
this lawgiving form, rather than that acting on them would achieve
some end or goal that would satisfy a desire (5:27). For example, I
should help others in need not, at bottom, because doing so would make
me feel good, even if it would, but rather because it is right; and it
is right (or permissible) to help others in need because this maxim
can be willed as a universal law.



Although Kant holds that the morality of an action depends on the form
of its maxim rather than its end or goal, he nevertheless claims both
that every human action has an end and that we are unavoidably
concerned with the consequences of our actions (4:437; 5:34;
6:5-7, 385). This is not a moral requirement but simply part of
what it means to be a rational being. Moreover, Kant also holds the
stronger view that it is an unavoidable feature of human reason that
we form ideas not only about the immediate and near-term consequences
of our actions, but also about ultimate consequences. This is the
practical manifestation of reason's general demand for what Kant
calls "the unconditioned"
 (5:107-108).[23]
 In particular, since we naturally have desires and inclinations, and
our reason has "a commission" to attend to the
satisfaction of our desires and inclinations, on Kant's view we
unavoidably form an idea of the maximal satisfaction of all our
inclinations and desires, which he calls happiness (5:61, 22, 124).
This idea is indeterminate, however, since nobody can know "what
he really wishes and wills" and thus what would make him
completely happy (4:418). We also form the idea of a moral world or
realm of ends, in which everyone acts only in accordance with maxims
that can be universal laws (A808/B836, 4:433ff.).



But neither of these ideas by itself expresses our unconditionally
complete end, as human reason demands in its practical use. A
perfectly moral world by itself would not constitute our "whole
and complete good [...] even in the judgment of an impartial
reason," because it is human nature also to need happiness
(5:110, 25). And happiness by itself would not be unconditionally
good, because moral virtue is a condition of worthiness to be happy
(5:111). So our unconditionally complete end must combine both virtue
and happiness. In Kant's words, "virtue and happiness
together constitute possession of the highest good in a person, and
happiness distributed in exact proportion to morality (as the worth of
a person and his worthiness to be happy) constitutes the *highest
good* of a possible world" (5:110-111). It is this
ideal world combining complete virtue with complete happiness that
Kant normally has in mind when he discusses the highest good.



Kant says that we have a duty to promote the highest good, taken in
this sense (5:125). He does not mean, however, to be identifying some
new duty that is not derived from the moral law, in addition to all
the particular duties we have that are derived from the moral
 law.[24]
 For example, he is not claiming that in addition to my duties to help
others in need, not to commit theft, etc., I also have the additional
duty to represent the highest good as the final end of all moral
conduct, combined with happiness, and to promote that end. Rather, as
we have seen, Kant holds that it is an unavoidable feature of human
reasoning, instead of a moral requirement, that we represent all
particular duties as leading toward the promotion of the highest good.
So the duty to promote the highest good is not a particular duty at
all, but the sum of all our duties derived from the moral law -
it "does not increase the number of morality's duties but
rather provides these with a special point of reference for the
unification of all ends" (6:5). Nor does Kant mean that anyone
has a duty to realize or actually bring about the highest good through
their own power, although his language sometimes suggests this (5:113,
122). Rather, at least in his later works Kant claims that only the
common striving of an entire "ethical community" can
actually produce the highest good, and that the duty of individuals is
to promote (but not single-handedly produce) this end with all of
their strength by doing what the moral law commands (6:97-98,
 390-394).[25]



Finally, according to Kant we must conceive of the highest good as a
possible state of affairs in order to fulfill our duty to promote it.
Here Kant does not mean that we unavoidably represent the highest good
as possible, since his view is that we must represent it as possible
only if we are to fulfill our duty of promoting it, and yet we may
fail at doing our duty. Rather, we have a choice about whether to
conceive of the highest good as possible, to regard it as impossible,
or to remain noncommittal (5:144-145). But we can fulfill our
duty of promoting the highest good only by choosing to conceive of the
highest good as possible, because we cannot promote any end without
believing that it is possible to achieve that end (5:122). So
fulfilling the sum of all moral duties to promote the highest good
requires believing that a world of complete virtue and happiness is
not simply "a phantom of the mind" but could actually be
realized (5:472).


### 6.2 The postulates of pure practical reason



Kant argues that we can comply with our duty to promote the highest
good only if we believe in the immortality of the soul and the
existence of God. This is because to comply with that duty we must
believe that the highest good is possible, and yet to believe that the
highest good is possible we must believe that the soul is immortal and
that God exists, according to
 Kant.[26]




Consider first Kant's moral argument for belief in immortality.
The highest good, as we have seen, would be a world of complete
morality and happiness. But Kant holds that it is impossible for
"a rational being of the sensible world" to exhibit
"complete conformity of dispositions with the moral law,"
which he calls "holiness," because we can never extirpate
the propensity of our reason to give priority to the incentives of
inclination over the incentive of duty, which propensity Kant calls
radical evil (5:122, 6:37). Kant claims that the moral law
nevertheless requires holiness, however, and that it therefore
"can only be found in an endless progress toward that complete
conformity," or progress that goes to infinity (5:122). This
does not mean that we can substitute endless progress toward complete
conformity with the moral law for holiness in the concept of the
highest good, but rather that we must represent that complete
conformity as an infinite progress toward the limit of holiness. Kant
continues: "This endless progress is, however, possible only on
the presupposition of the existence and personality of the same
rational being continuing endlessly (which is called the immortality
of the soul). Hence the highest good is practically possible only on
the presupposition of the immortality of the soul, so that this, as
inseparable with the moral law, is a postulate of pure practical
reason" (ibid.). Kant's idea is not that we should imagine
ourselves attaining holiness later although we are not capable of it
in this life. Rather, his view is that we must represent holiness as
continual progress toward complete conformity of our dispositions with
the moral law that begins in this life and extends into infinity.



Kant's moral argument for belief in God in the *Critique of
Practical Reason* may be summarized as follows. Kant holds that
virtue and happiness are not just combined but necessarily combined in
the idea of the highest good, because only possessing virtue makes one
worthy of happiness - a claim that Kant seems to regard as part
of the content of the moral law (4:393; 5:110, 124). But we can
represent virtue and happiness as necessarily combined only by
representing virtue as the efficient cause of happiness. This means
that we must represent the highest good not simply as a state of
affairs in which everyone is both happy and virtuous, but rather as
one in which everyone is happy because they are virtuous
(5:113-114, 124). However, it is beyond the power of human
beings, both individually and collectively, to guarantee that
happiness results from virtue, and we do not know any law of nature
that guarantees this either. Therefore, we must conclude that the
highest good is impossible, unless we postulate "the existence
of a cause of nature, distinct from nature, which contains the ground
of this connection, namely the exact correspondence of happiness with
morality" (5:125). This cause of nature would have to be God
since it must have both understanding and will. Kant probably does not
conceive of God as the efficient cause of a happiness that is rewarded
in a future life to those who are virtuous in this one. Rather, his
view is probably that we represent our endless progress toward
holiness, beginning with this life and extending into infinity, as the
efficient cause of our happiness, which likewise begins in this life
and extends to a future one, in accordance with teleological laws that
God authors and causes to harmonize with efficient causes in nature
(A809-812/B837-840; 5:127-131, 447-450).



Both of these arguments are subjective in the sense that, rather than
attempting to show how the world must be constituted objectively in
order for the highest good to be possible, they purport to show only
how we must conceive of the highest good in order to be subjectively
capable both of representing it as possible and of fulfilling our duty
to promote it. But Kant also claims that both arguments have an
objective basis: first, in the sense that it cannot be proven
objectively either that immortality or God's existence are
impossible; and, second, in the sense that both arguments proceed from
a duty to promote the highest good that is based not on the subjective
character of human reason but on the moral law, which is objectively
valid for all rational beings. So while it is not, strictly speaking,
a duty to believe in God or immortality, we must believe both in order
to fulfill our duty to promote the highest good, given the subjective
character of human reason.



To see why, consider what would happen if we did not believe in God or
immortality, according to Kant. In the *Critique of Pure
Reason*, Kant seems to say that this would leave us without any
incentive to be moral, and even that the moral law would be invalid
without God and immortality (A813/B841, A468/B496). But Kant later
rejects this view (8:139). His mature view is that our reason would be
in conflict with itself if we did not believe in God and immortality,
because pure practical reason would represent the moral law as
authoritative for us and so present us with an incentive that is
sufficient to determine our will; but pure theoretical (i.e.,
speculative) reason would undermine this incentive by declaring
morality an empty ideal, since it would not be able to conceive of the
highest good as possible (5:121, 143, 471-472, 450-453).
In other words, the moral law would remain valid and provide any
rational being with sufficient incentive to act from duty, but we
would be incapable of acting as rational beings, since "it is a
condition of having reason at all [...] that its principles and
affirmations must not contradict one another" (5:120). The only
way to bring speculative and practical reason "into that
relation of equality in which reason in general can be used
purposively" is to affirm the postulates on the grounds that
pure practical reason has primacy over speculative reason. This means,
Kant explains, that if the capacity of speculative reason "does
not extend to establishing certain propositions affirmatively,
although they do not contradict it, as soon as these same propositions
belong inseparably to the practical interest of pure reason it must
accept them [...,] being mindful, however, that these are not its
insights but are yet extensions of its use from another, namely a
practical perspective" (5:121). The primacy of practical reason
is a key element of Kant's response to the crisis of the
Enlightenment, since he holds that reason deserves the sovereign
authority entrusted to it by the Enlightenment only on this basis.


## 7. The unity of nature and freedom



This final section briefly discusses how Kant attempts to unify the
theoretical and practical parts of his philosophical system in the
*Critique of the Power of Judgment*.


### 7.1 The great chasm



In the Preface and Introduction to the *Critique of the Power of
Judgment*, Kant announces that his goal in the work is to
"bring [his] entire critical enterprise to an end" by
bridging the "gulf" or "chasm" that separates
the domain of his theoretical philosophy (discussed mainly in the
*Critique of Pure Reason*) from the domain of his practical
philosophy (discussed mainly in the *Critique of Practical
Reason*) (5:170, 176, 195). In his words: "The understanding
legislates a priori for nature, as object of the senses, for a
theoretical cognition of it in a possible experience. Reason
legislates a priori for freedom and its own causality, as the
supersensible in the subject, for an unconditioned practical
cognition. The domain of the concept of nature under the one
legislation and that of the concept of freedom under the other are
entirely barred from any mutual influence that they could have on each
other by themselves (each in accordance with its fundamental laws) by
the great chasm that separates the supersensible from the
appearances" (5:195).



One way to understand the problem Kant is articulating here is to
consider it once again in terms of the crisis of the
 Enlightenment.[27]
 The crisis was that modern science threatened to undermine
traditional moral and religious beliefs, and Kant's response is
to argue that in fact these essential interests of humanity are
consistent with one another when reason is granted sovereignty and
practical reason is given primacy over speculative reason. But the
transcendental idealist framework within which Kant develops this
response seems to purchase the consistency of these interests at the
price of sacrificing a unified view of the world and our place in it.
If science applies only to appearances, while moral and religious
beliefs refer to things in themselves or "the
supersensible," then how can we integrate these into a single
conception of the world that enables us to transition from the one
domain to the other? Kant's solution is to introduce a third a
priori cognitive faculty, which he calls the reflecting power of
judgment, that gives us a teleological perspective on the world.
Reflecting judgment provides the concept of teleology or purposiveness
that bridges the chasm between nature and freedom, and thus unifies
the theoretical and practical parts of Kant's philosophy into a
single system (5:196-197).



It is important to Kant that a third faculty independent of both
understanding and reason provides this mediating perspective, because
he holds that we do not have adequate theoretical grounds for
attributing objective teleology to nature itself, and yet regarding
nature as teleological solely on moral grounds would only heighten the
disconnect between our scientific and moral ways of viewing the world.
Theoretical grounds do not justify us in attributing objective
teleology to nature, because it is not a condition of
self-consciousness that our understanding construct experience in
accordance with the concept of teleology, which is not among
Kant's categories or the principles of pure understanding that
ground the fundamental laws of nature. That is why his theoretical
philosophy licenses us only in attributing mechanical causation to
nature itself. To this limited extent, Kant is sympathetic to the
dominant strain in modern philosophy that banishes final causes from
nature and instead treats nature as nothing but matter in motion,
which can be fully described mathematically. But Kant wants somehow to
reconcile this mechanistic view of nature with a conception of human
agency that is essentially teleological. As we saw in the previous
section, Kant holds that every human action has an end and that the
sum of all moral duties is to promote the highest good. It is
essential to Kant's approach, however, to maintain the autonomy
of both understanding (in nature) and reason (in morality), without
allowing either to encroach on the other's domain, and yet to
harmonize them in a single system. This harmony can be orchestrated
only from an independent standpoint, from which we do not judge how
nature is constituted objectively (that is the job of understanding)
or how the world ought to be (the job of reason), but from which we
merely regulate or reflect on our cognition in a way that enables us
to regard it as systematically unified. According to Kant, this is the
task of reflecting judgment, whose a priori principle is to regard
nature as purposive or teleological, "but only as a regulative
principle of the faculty of cognition" (5:197).


### 7.2 The purposiveness of nature



In the *Critique of the Power of Judgment*, Kant discusses four
main ways in which reflecting judgment leads us to regard nature as
purposive: first, it leads us to regard nature as governed by a system
of empirical laws; second, it enables us to make aesthetic judgments;
third, it leads us to think of organisms as objectively purposive;
and, fourth, it ultimately leads us to think about the final end of
nature as a
 whole.[28]



First, reflecting judgment enables us to discover empirical laws of
nature by leading us to regard nature as if it were the product of
intelligent design (5:179-186). We do not need reflecting
judgment to grasp the a priori laws of nature based on our categories,
such as that every event has a cause. But in addition to these a
priori laws nature is also governed by particular, empirical laws,
such as that fire causes smoke, which we cannot know without
consulting experience. To discover these laws, we must form hypotheses
and devise experiments on the assumption that nature is governed by
empirical laws that we can grasp (Bxiii-xiv). Reflecting
judgment makes this assumption through its principle to regard nature
as purposive for our understanding, which leads us to treat nature as
if its empirical laws were designed to be understood by us
(5:180-181). Since this principle only regulates our cognition
but is not constitutive of nature itself, this does not amount to
assuming that nature really is the product of intelligent design,
which according to Kant we are not justified in believing on
theoretical grounds. Rather, it amounts only to approaching nature in
the practice of science as if it were designed to be understood by us.
We are justified in doing this because it enables us to discover
empirical laws of nature. But it is only a regulative principle of
reflecting judgment, not genuine theoretical knowledge, that nature is
purposive in this way.



Second, Kant thinks that aesthetic judgments about both beauty and
sublimity involve a kind of purposiveness, and that the beauty of
nature in particular suggests to us that nature is hospitable to our
ends. According to his aesthetic theory, we judge objects to be
beautiful not because they gratify our desires, since aesthetic
judgments are disinterested, but rather because apprehending their
form stimulates what he calls the harmonious "free play"
of our understanding and imagination, in which we take a distinctively
aesthetic pleasure (5:204-207, 217-218, 287). So beauty is
not a property of objects, but a relation between their form and the
way our cognitive faculties work. Yet we make aesthetic judgments that
claim intersubjective validity because we assume that there is a
common sense that enables all human beings to communicate aesthetic
feeling (5:237-240, 293-296). Beautiful art is
intentionally created to stimulate this universally communicable
aesthetic pleasure, although it is effective only when it seems
unintentional (5:305-307). Natural beauty, however, is
unintentional: landscapes do not know how to stimulate the free play
of our cognitive faculties, and they do not have the goal of giving us
aesthetic pleasure. In both cases, then, beautiful objects appear
purposive to us because they give us aesthetic pleasure in the free
play of our faculties, but they also do not appear purposive because
they either do not or do not seem to do this intentionally. Kant calls
this relation between our cognitive faculties and the formal qualities
of objects that we judge to be beautiful "subjective
purposiveness" (5:221). Although it is only subjective, the
purposiveness exhibited by natural beauty in particular may be
interpreted as a sign that nature is hospitable to our moral interests
(5:300). Moreover, Kant also interprets the experience of sublimity in
nature as involving purposiveness. But in this case it is not so much
the purposiveness of nature as our own purpose or
"vocation" as moral beings that we become aware of in the
experience of the sublime, in which the size and power of nature stand
in vivid contrast to the superior power of our reason
(5:257-260, 267-269).



Third, Kant argues that reflecting judgment enables us to regard
living organisms as objectively purposive, but only as a regulative
principle that compensates for our inability to fully understand them
mechanistically, which reflects the limitations of our cognitive
faculties rather than any intrinsic teleology in nature. We cannot
fully understand organisms mechanistically because they are
"self-organizing" beings, whose parts are "combined
into a whole by being reciprocally the cause and effect of their
form" (5:373-374). The parts of a watch are also possible
only through their relation to the whole, but that is because the
watch is designed and produced by some rational being. An organism, by
contrast, produces and sustains itself, which is inexplicable to us
unless we attribute to organisms purposes by analogy with human art
(5:374-376). But Kant claims that it is only a regulative
principle of reflecting judgment to regard organisms in this way, and
that we are not justified in attributing objective purposiveness to
organisms themselves, since it is only "because of the peculiar
constitution of my cognitive faculties [that] I cannot judge about the
possibility of those things and their generation except by thinking of
a cause for these acts in accordance with intentions"
(5:397-398). Specifically, we cannot understand how a whole can
be the cause of its own parts because we depend on sensible intuition
for the content of our thoughts and therefore must think the
particular (intuition) first by subsuming it under the general (a
concept). To see that this is just a limitation of the human,
discursive intellect, imagine a being with an intuitive understanding
whose thought does not depend, as ours does, on receiving sensory
information passively, but rather creates the content of its thought
in the act of thinking it. Such a (divine) being could understand how
a whole can be the cause of its parts, since it could grasp a whole
immediately without first thinking particulars and then combining them
into a whole (5:401-410). Therefore, since we have a discursive
intellect and cannot know how things would appear to a being with an
intuitive intellect, and yet we can only think of organisms
teleologically, which excludes mechanism, Kant now says that we must
think of both mechanism and teleology only as regulative principles
that we need to explain nature, rather than as constitutive principles
that describe how nature is intrinsically constituted (5:410ff.).



Fourth, Kant concludes the *Critique of the Power of Judgment*
with a long appendix arguing that reflecting judgment supports
morality by leading us to think about the final end of nature, which
we can only understand in moral terms, and that conversely morality
reinforces a teleological conception of nature. Once it is granted on
theoretical grounds that we must understand certain parts of nature
(organisms) teleologically, although only as a regulative principle of
reflecting judgment, Kant says we may go further and regard the whole
of nature as a teleological system (5:380-381). But we can
regard the whole of nature as a teleological system only by employing
the idea of God, again only regulatively, as its intelligent designer.
This involves attributing what Kant calls external purposiveness to
nature - that is, attributing purposes to God in creating nature
(5:425). What, then, is God's final end in creating nature?
According to Kant, the final end of nature must be human beings, but
only as moral beings (5:435, 444-445). This is because only
human beings use reason to set and pursue ends, using the rest of
nature as means to their ends (5:426-427). Moreover, Kant claims
that human happiness cannot be the final end of nature, because as we
have seen he holds that happiness is not unconditionally valuable
(5:430-431). Rather, human life has value not because of what we
passively enjoy, but only because of what we actively do (5:434). We
can be fully active and autonomous, however, only by acting morally,
which implies that God created the world so that human beings could
exercise moral autonomy. Since we also need happiness, this too may be
admitted as a conditioned and consequent end, so that reflecting
judgment eventually leads us to the highest good (5:436). But
reflection on conditions of the possibility of the highest good leads
again to Kant's moral argument for belief in God's
existence, which in turn reinforces the teleological perspective on
nature with which reflecting judgment began.



Thus Kant argues that although theoretical and practical philosophy
proceed from separate and irreducible starting points -
self-consciousness as the highest principle for our cognition of
nature, and the moral law as the basis for our knowledge of freedom
- reflecting judgment unifies them into a single, teleological
worldview that assigns preeminent value to human autonomy.