## 1. Biographical Sketch



Christian Wolff was born 24 January 1679 in Breslau in the province of
Silesia (now part of Poland) to parents of modest
 means.[1]
 Wolff was educated at the Lutheran-humanist
Maria-Magdelena-Gymansium, where his teachers included Christian
Gryphius (1649-1706), a baroque poet and dramatist, and Caspar
Neumann (1648-1715), the latter of whom Wolff credited with
introducing him to the Cartesian philosophy. In 1699, Wolff enrolled
at the University of Jena, where he pursued a course of study in
theology, physics, and mathematics, moving from there to Leipzig in
1702 where he would sit the *Magisterexamen* and then complete
his *Habilitationsschrift* in 1703 entitled: *Philosophia
practica universalis, methodo mathematica conscripta* (On
Universal Practical Philosophy, composed according to the Mathematical
Method). Otto Mencke (1644-1707), the founder of the learned
journal *Acta eruditorum*, served as an examiner for the
dissertation and, impressed, sent it to Leibniz, with whom Wolff
subsequently struck up a correspondence that continued until Leibniz's death in 1716.



Due in part to Leibniz's support, Wolff was soon offered, and
accepted, a position in Giessen (though he had also been offered
positions at Danzig and Wismar) which he intended to take up after
visiting his family in Breslau. However, on his homeward journey the
occupation of Saxony by Charles XII of Sweden required Wolff to take a
detour through nearby Halle in Prussia, whose recently founded
university also happened to be in need of a professor of mathematics.
Wolff was offered the position and, again with Leibniz's
assistance, was able to extricate himself from his commitment to
Giessen, delivering his inaugural lecture at Halle in early 1707.
During the next 15 years he enjoyed a prolific period, publishing and
lecturing at first primarily in mathematics and natural science,
though he began to lecture in philosophy proper around
 1710.[2]
 Wolff's first major philosophical textbook was published in
1713, the *Vernunfftige Gedancken von den Krafften des
menschlichen Verstandes und ihrem richtigen Gebrauche in
Erkantnis der Wahrheit* (Rational Thoughts on the Powers of
the Human Understanding and its Propert Use in the Cognition of Truth)
[the *German Logic*, hereafter GL]. In 1720, Wolff published
his German textbook on metaphysics, the *Vernunftige Gedanken
von Gott, der Welt und der Seele des Menschen, auch allen Dingen
uberhaupt* (Rational Thoughts on God, the World and the Soul
of Man, and on All Things in General) [the *German
Metaphysics*, hereafter GM]. These were followed by further German
textbooks on ethics (1720), politics (1721), and physics (1723).



Wolff's expanding philosophical activity, especially concerning
topics in natural theology, as well as his popularity as a lecturer
and growing influence within the university drew the ire of his
Pietist colleagues in the faculty of theology, including August
Hermann Francke (1663-1723), the founder of the famous
*Waisenhaus* (orphanage), and Joachim Lange (1670-1744).
They took exception to a number of doctrines expressed in
Wolff's *German Metaphysics*, including its privileging
of the intellect to the will, its apparent demotion of freedom to mere
spontaneity, and the diminished role played by revelation in matters
of theological interest. While the Pietists were at first content to
wage a behind-the-scenes campaign, Wolff's address as outgoing
rector of the university on 12 July 1721, in which he defended the
reasonableness of Confucian moral philosophy, led to a significant
escalation of the dispute. Wolff, asserting the independence of the
philosophical faculty, refused to submit the text of his lecture for
subsequent examination by the faculty of theology, a conflict that
came to involve the university senate and even king Frederick Wilhelm
I (the "soldier king") himself. While Wolff enjoyed the
support of officials within the royal court, the Pietists exploited
their personal connections with the king, who was ultimately persuaded
that Wolff's endorsement of the pre-established harmony
represented a threat to military discipline (as the acts of deserters
would be pre-established and so not subject to sanction). On 8
November 1723, the king issued an edict removing Wolff from his
university position and ordering him to leave Prussia within 48 hours
on pain of hanging. The edict was received in Halle four days later,
and Wolff immediately left Prussian lands on 12 November 1723.



While Wolff's Pietist colleagues celebrated Wolff's exile
(reportedly even from the pulpit), it ultimately served only to
enhance Wolff's reputation, bringing him to the attention of
luminaries of the Enlightenment, including Voltaire. He was
immediately offered positions in Leipzig and Marburg, the latter of
which he accepted though a special exemption had to be granted to
allow a Lutheran to teach at a Reformed university. And even as the
dispute with his critics continued, generating a substantial
literature in its own right, Wolff managed during his Marburg years to
complete a reworked Latin presentation of his theoretical philosophy
intended to make his ideas available to a pan-European audience. These
texts include: *Philosophia rationalis sive Logica*
(*Rational Philosophy, or Logic*) of 1728 [the *Latin
Logic*, hereafter LL], the first part of which is the
*Discursus praeliminaris de philosophia in genere*
(*Preliminary Discourse on Philosophy in General*) [DP]; the
*Philosophia prima sive Ontologia* (*First Philosophy, or
Ontology*) of 1730 [Ont.]; *Cosmologia generalis*
(*General Cosmology*) of 1731 [Cosm.]; *Psychologia
empirica* (*Empirical Psychology*) of 1732 [EP]; the
*Psychologia rationalis* (*Rational Psychology*) of 1734
[RP]; and the two-volume *Theologia naturalis* (*Natural
Theology*) of 1736-37 [NT].



Friedrich Wilhelm I eventually thought better of his precipitous
action against Wolff, as he attempted in 1733 to entice him
(unsuccessfully) back to Halle and in 1736 lifted a prohibition he had
enacted against the teaching of Wolffian texts. However, Wolff
remained in Marburg, collecting tributes and memberships in learned
societies, until the ascension of Friedrich Wilhelm I's son,
Friedrich II (the Great), himself an enlightened monarch and admirer
of Wolff. Wolff accepted the new king's offer of a
professorship and vice-chancellorship at his previous institution in
Halle and returned to the city on 6 December 1740 to take up his new
position. Wolff continued to lecture and publish actively, with his
later efforts devoted particularly to works on the law of peoples,
natural law, and ethics. He died in Halle on 9 April 1754.


## 2. Philosophical Sources and Relationship with Leibniz



Wolff's wide intellectual interests saw him exposed to a diverse
set of influences. Neumann not only acquainted Wolff during his time
at Gymansium with the Cartesian philosophy but impressed on him the
need for "mathematical" treatments of philosophical topics
(including natural theology and practical philosophy). Wolff also
familiarized himself with late Scholastic philosophy, through a
textbook by Johannes Scharf (1595-1660), a follower of Suarez;
indeed, Wolff's mastery of Scholastic thinking was displayed in
his successful disputations with students at the rival (Catholic)
St.-Elizabeth-Gymnasium. While Wolff's own later philosophy
would likewise be branded a form of scholasticism, or
*Schulphilosophie*, the extent of the influence of Scholastic
philosophers, such as Suarez, upon his thought is debated
(Ecole 2001, Leduc 2018). Wolff's interest in mathematics
was encouraged by his teachers, which interest ultimately brought him
to Jena where he attended classes from G. A. Hamberger
(1662-1716), the successor of Erhard Weigel (1625-99); he
also studied a Euclidean textbook by J. C. Sturm (1635-1703),
though his reflection on its obscurities reportedly brought him his
"first light concerning the ancient method of
demonstration" (Wuttke 1841: 122-3).



A rather important if under-appreciated early influence on
Wolff's thinking, particularly concerning scientific method, was
Ehrenfried Walther von Tschirnhaus (1651-1708). Tschirnhaus, a
Saxon nobleman, studied at the University of Leiden where the
Cartesian Geulincx was
 active,[3]
 and was an important member of Spinoza's circle of friends
(among whom he circulated the *Ethics*). Yet, Tschirnhaus was
also an active scientist, mathematician, and inventor, who among other
things played a (perhaps *the*) key role in the discovery of
the secret for making porcelain. Tschirnhaus' principal
philosophical work is his *Medicina mentis* (1687,
2nd ed. 1695), and he characterizes his aim there as
outlining a "certain and constant method" for the
discovery of all unknown truths. Wolff first gained an interest in
reading the *Medicina mentis* while at Gymnasium, but it was
only after taking up his mathematical studies in Jena in 1699 that he
found himself able to profit from reading it. Wolff evidently read the
text with great interest and care, marking his own copy with comments
and queries and later preparing an excerpted text for use in lectures
for students without the requisite mathematical background. Wolff even
sought out Tschirnhaus himself during an Easter book fair in Leipzig
to press him with his concerns relating to his method. (After
Tschirnhaus' death in 1708 Wolff inquired as to the status of
his manuscripts but was disappointed to learn that, like Spinoza, he
had ordered them destroyed).



It was G. W. Leibniz, however, who would exercise the most
consequential influence on Wolff, both professionally (as seen above)
and philosophically. Wolff is often described as a disciple or
follower of Leibniz, a characterization for which there is some
justification. So, central tenets of Wolff's philosophical
system closely resemble those advanced by Leibniz. The commitment to
metaphysics, the extensive use of the principle of sufficient reason,
and the (qualified) endorsement of the pre-established harmony are
among many striking points of agreement. Indeed, Wolff appears not
only to accept the principles and methods of analysis posed by
Leibniz, but he also identifies opponents to his system, such as
Descartes, Spinoza, and the Atomists, that Leibniz opposed in his
own.



To describe Wolff as merely a disciple of Leibniz, however, is
misleading in several respects. First and foremost, this
characterization undercuts the important philosophical differences
that existed between the two men. Second it misconstrues the nature of
their relationship and the type of intellectual exchange that
transpired between them. During the early part of Wolff's
career, and the period when he corresponded with Leibniz,
Wolff's primary focus was in the field of mathematics. It is
maintained that Wolff was the first to teach calculus formally in
Germany (Beck 1969: 257). According to Wolff's own report
(Wuttke 1841: 146), when he arrived at Halle in 1707, mathematics was
"entirely neglected, nay quite unknown, in that
place". With the
exception of his *German Logic*, Wolff's energy early in
his career was directed at producing a four-volume *Elements of All
the Mathematical Sciences* [German edition 1710, and Latin edition
1713] as well as a *Mathematical Lexicon* [1716]. In this
light, it is perhaps not surprising to find the bulk of the
Wolff-Leibniz correspondence dedicated to issues in mathematics.
Although they also exchanged ideas on philosophical topics (for
discussion, see Rutherford 2004), their philosophical
correspondence centered primarily on ethics and philosophical
theology.



Leibniz published his *Theodicy* in 1710, and this work
remained the only extended presentation of his philosophical ideas
published in his lifetime. Apart from a handful of other smaller
articles written on philosophical topics, most notably,
*Meditations on Knowledge, Truth, and Ideas* [1684], *A
Specimen of Dynamics* [1695], and *On Nature Itself*
[1698], there were relatively few texts available, and hardly any from
what is regarded today as the core of Leibniz's *corpus*,
from which Wolff could have extracted a definitive statement of
Leibniz's philosophy. Consider a remark by Leibniz to Nicolas
Remond, in a letter dated July 1714:



> 
> 
> Mr. Wolff has adopted some of my opinions, but since he is very busy
> with teaching, especially in mathematics, and we have not had much
> correspondence together on philosophy, he can know very little about
> my opinions beyond those which I have published. (Leibniz 1989b:
> 657)
> 
> 
> 



The philosophical works by Leibniz that we typically consider today to
represent his mature philosophical views were published posthumously.
*The Principles of Nature and Grace* appeared in 1718, *The
Monadology* in 1720, and the *New Essays Concerning Human
Understanding* as late as 1765. Although the early Kant and later
German thinkers had the benefit of these texts, Wolff had no such
luxury when writing his *German Metaphysics* in 1719.



What is significant about considering the relationship between Wolff
and Leibniz is that although there is clear evidence that Leibniz was
a direct influence on Wolff, there is also equal evidence that
testifies to Wolff's independence from Leibniz, particularly
when Wolff was formulating and first presenting his philosophical
views (cf. Corr 1975 for an influential discussion). Recognizing
Wolff's independence is perhaps important for understanding what
Kant and his contemporaries understood by the expression
"Leibnizian-Wolffian philosophy". Instead of taking this
expression to mean "the philosophy of Leibniz, interpreted and
presented by Wolff and his followers", as it commonly is, it is
perhaps preferable to understand the expression to mean
"Wolff's philosophical system, variously corrected and
improved through the posthumously discovered views of
Leibniz".


## 3. Wolff on Philosophy, Science, and Method



Early in his career, until shortly after his expulsion from Halle,
Wolff primarily presented his work in the German vernacular. His
reasons for choosing German, rather than Latin, the standard languages
for academic texts in Germany at the time, were both tactical and
theoretical. Before Wolff, there were very few philosophical works
written in German. By providing treatises on logic and metaphysics,
Wolff was able to service a noticeable gap in the German university
curriculum while at the same time promoting his own philosophical
agenda. Prior to Wolff's contributions, the standard text books
in philosophy were largely outdated Lutheran-scholastic treatises
modeled after the treatises of Philipp Melanchthon (1497-1560)
(cf. Beck 1969: 189-94, 101-10). Unlike English and French
universities, which had set aside hidebound scholasticism and embraced
modern ideas and systems, German universities (often under the direct
jurisdiction of local theological authorities) were slow to make such
a change.



But Wolff also had deep-seated theoretical reasons for writing a
German-language philosophy. He believed that the goal and purpose of
philosophy should not only be rooted in what he calls "the
pursuit of the knowledge of the truth" but also in its utility
and the practical value it has for humans in their everyday life. In
the preface to his *German Logic*, he writes: 



> 
> 
> a person should learn philosophy ...[not with] a view to the
> vicious taste of the schools for idle disputation and wrangling, but
> in order to [enjoy its] usefulness in future life.... (GL:
> lxxvii; cf. also Corr 1970) 
> 
> 
> 



By writing a German-language philosophy, Wolff sought to transform
philosophy from a discipline that had become mired in formalism and
centered around traditionally defined topics to a discipline that had
genuine utility for German students.



Among the practical aims of Wolff's philosophy is outfitting the
mind with the tools it needs to pursue and attain properly scientific
knowledge, in contrast with "common" or
"vulgar" knowledge, or as Wolff sometimes says "the
natural way of thinking". If certain groups of facts can be
shown to follow from "well-grounded" assumptions according
to strict requirements of demonstration, the class of facts is deemed
by Wolff to constitute a "science". Wolff gives several
definitions of the term science:



> 
> 
> By science, I understand, that habit of the understanding, whereby, in
> a manner not to be refuted, we establish our assertions on
> irrefragable grounds or principles (GL: c. 1, SS2).
> 
> 
> 
> By science here I mean the habit of demonstrating propositions, i.e.,
> the habit of inferring conclusions by legitimate sequence from certain
> and immutable principles (DP: SS30).
> 
> 
> 
> Science is the capacity to prove from indisputable grounds everything
> one asserts or, in a word, the capacity to demonstrate; and in
> demonstration truths are connected together; therefore through science
> one knows the connection of truths, and thus science comes from reason
> (GM: SS383).
> 
> 
> 



While Wolff emphasizes that science is a "habit of the
understanding", this should be taken to also involve the human
capacity of *reason*, inasmuch as it is the faculty for
perceiving the connection between truths. When properly employed,
then, human reason can discern groups of facts, establish a certain
order and interconnectedness between these facts, and ultimately
justify them as being certain parts of human knowledge. Put slightly
differently, science is a disposition or ability of the human mind to
conceive the facts of reality in an ordered and structured way.
Individual sciences, therefore, such as theology, cosmology, or
psychology, are simply the various sets, or subsets of demonstrable
cognitions and the principles (including axioms, definitions, and
empirical facts) from which they are derived.



Wolff's system is also structured according to a notion of
rational order. The "order of science" pertains to the
relationship not only between individual sciences but also between the
sets of discoverable facts within each given discipline (cf. DP:
SSSS132-5). The central idea here is that certain truths
are known prior to, and serve as a basis for discovering, other
truths. And just as there are certain facts that are more fundamental
and serve as a basis for discovering other facts, there are, Wolff
believes, certain sciences whose subject matter is more basic and
which ultimately stand as the foundation for other sciences that have
a more specialized focus. For example, in the "order of
demonstration", physics follows general cosmology which, in
turn, follows ontology (or first philosophy) (DP:
SSSS94-5).



It appears, at first glance, that Wolff's insistence on the
rational order of science simply follows from a dogmatic metaphysical
claim about the structure of reality. A reasonable objection to Wolff
might be that his conception of the rational order of science is based
on an unwarranted assumption about the harmonious order he believes to
be present in all facets of reality. This harmonious order (the
objection continues) illicitly presupposes that a divine architect has
created everything according to a plan and thus the rational order of
human science is simply an upshot of God's creative power. There
are certainly passages of Wolff's works that lend support to
such an objection (see for instance GL: c. 16, SS3). However, to
reduce Wolff's view of the rational order of science to simply a
dogmatic metaphysical claim really ignores the practical and common
sense dimensions to his thought. An important part of the reason why
Wolff believes that there is a rational order to science is because of
the progress he believes he has witnessed in such sciences as
astronomy and optics, which he believes have utilized such an order
when establishing various scientific truths (DP: SS139). By virtue
of the very interconnectedness of the different disciplines (most
notably, mathematics with physics and physics with astronomy) the
claim for an intrinsic rational order among the sciences is seen by
Wolff to be a pragmatic explanation for what is already largely
observed and accepted as the *status quo* among many natural
philosophers (GL: c. 1, SS39). Unlike Leibniz, Wolff was much more
willing to embrace the advances brought in the name of Newtonian
natural philosophy (on this, see the next section).



Wolff gives the following definition of philosophy in his *German
Logic*: "[p]hilosophy is the *science* of all
possible things, together with the manner and reason of their
possibility" (Preface, SS1). Now because of its subject
matter, philosophy is considered by Wolff to be the broadest and most
fundamental science. In the classification of sciences given in his
*Preliminary Discourse*, Wolff first divides philosophy into
two branches: practical philosophy, on one hand, and theoretical
philosophy, on the other. Practical philosophy deals (in general) with
human actions and includes morality, politics, jurisprudence, and
economics. Theoretical philosophy, by contrast, deals with sets of
possible and actual objects and is (itself) divided into three
separate branches: (1) ontology, or metaphysics *proper*, (2)
"special" metaphysics, which includes general cosmology,
psychology and natural theology, and (3) physics (DP: SS92).
Whereas ontology and general cosmology are considered by Wolff to be
completely "pure" (or *a priori*) sciences,
psychology, natural theology, and physics are considered to be based
upon empirical (i.e., historical) principles. As a brief aside, Wolff
and the Critical Kant hold very different views on the relationship
between practical and theoretical philosophy. Whereas Wolff believes
that all of practical philosophy is subordinated to metaphysics (i.e.,
ontology as well as the three sub-disciplines that comprise special
metaphysics), the Critical Kant argues for the independence of
practical from theoretical principles. Wolff, in stark contrast,
maintains that discoveries and conclusions made in practical
philosophy are necessarily based upon prior conclusions drawn from
ontology or metaphysics.



Before turning to an examination of Wolff's theoretical
philosophy, and metaphysics in particular, it will be helpful to first
consider Wolff's distinctive, and often misunderstood,
rationalism.


## 4. Wolffian Rationalism



Philosophical rationalism can be understood to involve any or all of
the following: commitment to the existence of innate ideas or
principles, the privileging of *a priori* cognition to
cognition known *a posteriori*, and endorsement of the
principle of sufficient reason (*PSR*). Even though Wolff is
officially agnostic regarding innate ideas, *a priori*
cognition (at least in the traditional sense of a cognition *from
grounds*) enjoys a privileged place in his system, and to be sure,
*PSR* is central to Wolff's entire exposition of
metaphysics and figures prominently in all levels of his philosophical
system. Wolff is, accordingly, correctly identified as a philosophical
rationalist; yet, this label has often inspired misleading
characterizations of Wolff's thought as abjuring all reliance
upon experience in the aim of constructing a pure intellectual system
founded solely on the principle of contradiction. Such a caricature,
however persistent, is to be firmly rejected on both historical and
philosophical grounds.



Historically, this misrepresentation of Wolff as an arch-rationalist
ignores his liberal borrowings from, and deep engagement with,
empiricistic and scientifically-minded thinkers, most notably Locke
and Newton. In his capacity as reviewer for the *Acta
eruditorum*, Wolff was intimately familiar with intellectual
developments in England--indeed he was brought on by Mencke
specifically in order to comment on the mathematical and scientific
developments there (for which task Wolff taught himself English over a
Summer)--and he wrote approving early reviews of Newton's
*Optics* and Locke's *Opera posthuma*. In general,
Wolff took Locke's "historical, plain method" as a
model for his own empirical psychology, and admired the blending of
reason and experiment that characterized Newton's method, even
if Wolff was deeply skeptical of Newton's speculative and
metaphysical excursions in the Queries in the Latin edition of the
*Optics* and in the General Scholium of the second edition of
the *Principia* (not to mention the metaphysical views
explicitly defended by Samuel Clarke in the correspondence with
Leibniz, for the German edition of which Wolff wrote the preface).
Even so, Wolff's importance for the reception of Locke in
Germany is currently under-appreciated (*vide* Fischer 1975),
and his contributions to the reception of Newton have only recently
been explored in some detail (see Dunlop 2013, Stan 2012).



It might nonetheless be thought that Wolff's philosophy itself
does not reflect this engagement with empiricism. Indeed, Wolff
himself gives this impression when he states in the *German
Metaphysics* that experience is opposed to reason such that they
constitute "two paths to truth" (GM: SS372), and while
the path of experience might suffice for the concerns of ordinary
life, Wolff makes clear that the philosopher cannot rest content with
it but must use reason to press beyond what experience offers. That
this is so is reflected in Wolff's distinction between
"common knowledge or cognition [*gemeine
Erkantniss*]" and "the cognition of a philosopher
[*Erkanntniss eines Welt-Weisen*]" which he first
offers in the *German Logic*:



> 
> 
> It can now be seen how common cognition is distinguished from the
> cognition of a philosopher, namely, one who has no understanding of
> philosophy can learn many things about what is possible from
> experience, yet, he will not know how to indicate the reason why it
> [i.e., that which he learns from experience] can be. For instance, he
> learns from experience that it can rain, but cannot say how it happens
> [...] nor indicate the causes why it rains. (GL: Preface,
> SS6)
> 
> 
> 



This would suggest, then, that for Wolff the path to genuinely
philosophical truth is ultimately that of reason pursued independently
of experience.



Yet, a more careful look at Wolff's texts reveals that, rather
than representing completely divergent paths, reason and experience
are envisioned as forming a complementary whole, where experience
provides an indispensable basis for properly philosophical cognition
and even serves to confirm the latter's results. Indeed, the
important *dependence* of philosophical cognition upon
experiential cognition is emphasized in Wolff's later discussion
in the *Preliminary Discourse*. There, Wolff labels the
cognition of that which is and which happens *historical*
cognition (DP: SS3), and contends that cognition of the reason of
that which is or occurs, that is, philosophical cognition (DP:
SS6), frequently relies on historical cognition as its foundation
(*fundamenta*). This is the case, for instance, when we
discover by means of experience something that can serve as the ground
for something else that is or occurs (DP: SS10). Since that which
is known directly through experience is, for Wolff, "firm and
unshakeable" (DP: SS11), it follows that anyone who strives
for philosophical cognition should not neglect the historical, or as
Wolff claims, that 



> 
> 
> historical cognition should precede philosophical cognition and be
> constantly conjoined with it so that it does not lack a firm
> foundation. (DP: SS11; cf. Kreimendahl 2007)
> 
> 
> 



Unsurprisingly, Wolff sets up his distinctive emphasis on experience
and introduces his innovations in philosophical method in conscious
opposition to his rationalist predecessors. He faults Descartes, for
instance, for attempting to posit universal metaphysical principles
"from which one will deduce through the mere understanding
everything that is possible in nature" (Wolff 1723
[Preface]). Instead,
Wolff recommends near the end of the *German Logic* that the
philosopher should be trained 



> 
> 
> to draw determinate propositions from experience and with the help of
> some to find the ground of others, consequently, to unite reason with
> experience (GL: c. 16, SS11) 
> 
> 
> 



and later, in his oft-used metaphor, Wolff characterizes philosophical
cognition itself as a "marriage of reason and experience
[*connubium rationis et experientiae*]" (LL: SS1232;
cf. Cataldi Madonna 2001). Ideally, then, Wolff construes reason and
experience as converging toward a common end rather than constituting
divergent paths, and the philosopher is warned against pursuing one at
the expense of the other (DP: SS11). In this way, Wolff's
rationalism clearly separates itself from the spirit of classical
rationalism.


## 5. Metaphysics



Philosophy is a science of possible and actual reality. According to
Wolff's own taxonomy, theoretical philosophy is divided into
three separate branches: ontology (or metaphysics *proper*),
special metaphysics, and physics. Cosmology, as a branch of
metaphysics, is a special or restricted science insofar as its subject
matter deals with the "world-whole" rather than
"being in general" (the subject matter of ontology).
Although there is an important sense for Wolff in which ontology is
relevant for, and even necessarily grounds cosmology and the other
special sciences, cosmology (itself) stands in a grounding
relationship to physics that is, yet again, a more narrow and
specialized discipline (Cosm. SS121). Just as there are certain
principles and certain truths established in ontology that are
relevant for cosmology, there are certain principles and certain
truths established in cosmology that are relevant for the more
specialized science of physics. In fact, within Wolff's system
there is complete uniformity from the top-down (so to speak), so that
even principles of ontology are relevant for the discipline of
physics.


### 5.1 Ontology



Wolff's ontology is constructed on two foundational principles,
namely, the principle of contradiction [*PC* hereafter] and the
principle of sufficient reason. According to Wolff, *PC* is the
fundamental principle of human thought, the very first principle of
"all metaphysical first principles", and the "font
[or source] of all certitude" (Ont. SSSS54-5). It
is regarded by him to be a self-evident first principle, its truth
made manifest through our inability to think in a manner contrary to
it. In the *Ontologia*, he writes:



> 
> 
> SS27. We experience...[*PC*]... in the nature of
> our mind, in that, while it judges something to be, it is impossible
> at the same time to judge the same not to be....
> 
> 
> 
> SS28....[I]t cannot happen that the same thing simultaneously
> is and is not....
> 
> 
> 
> SS30....[For] ... contradiction is simultaneity in
> affirming and denying.
> 
> 
> 



*PC* is the "font of all certitude" insofar as, if
it were called into question, the most evident and secure judgments of
human knowledge, such as knowledge of the self (as a thinking thing),
could likewise be called into question. We recognize the fact of our
own existence by recognizing the psychological impossibility of
denying it. But if it were possible both to affirm and also deny our
own existence (simultaneously), then the experience of certitude that
accompanies this cognition would thereby be undermined.



Wolff contends that *PC* is not only for our thinking but, in
defining the limits of what is conceivable or not, also serves to
distinguish the possible from the impossible. So, impossibility,
defined formally, is that which involves a contradiction, whereas that
which does not is taken to be possible. Now for Wolff,
"possible" and "possible thing" are basically
synonymous terms. What is possible as a concept is simply reducible to
what is possible as a thing. The realm of concepts and the ontological
realm of objects converge in the Wolffian system (Kuehn 1997). A thing
or "being" is defined as "that which does not
involve a contradiction" (Ont. SS135). A possible concept,
consequently, is that which corresponds to a possible object (Ont.
SSSS57, 59, 60). This analysis of the concept of the possible
typifies Wolff's non-existential and essence-centered approach
to ontology. Very briefly, Wolff's understanding of being (or
what is) involves regarding being in its most general sense. A being
is "something" if and only if it is intrinsically
possible, and something is intrinsically possible, if and only if its
predicates or "determinations" are not contradictory.
"Nothing", in contrast, is simply a term that is empty of
all content. In the ontological realm of objects there is literally
*no thing* to which "nothing" corresponds (Ont.
SS57). Nothing, by definition, is not thinkable or
conceivable.



One important point to emphasize about Wolff's exposition of
ontology is that existence (or the actual reality of being) is
regarded exclusively as a determination or "complement" of
a possible thing (Ont. SS174). Although existing things are
included in his overall description of reality, they are not as a
class of objects his primary focus. More accurately, existing objects
figure into Wolff's metaphysical account only insofar as
existing objects are a subset of possible things.



With the notions of "possible thing",
"something", and "nothing" firmly in hand, we
can now explain the notion of reason (*Grund* or
*ratio*) that Wolff includes in his definition of philosophy.
Insofar as the subject matter of philosophy concerns the realm of all
possible things, Wolff believes that the task of the philosopher is to
provide "the manner and reason" of their possibility.
Warrant for this claim is grounded in the idea that everything,
whether possible or actual, has a "sufficient reason" for
why it is rather than not. In SS56 of his *Ontologia*, he
writes: "By sufficient reason we understand that from which it
is understood why something is [or can be]". Unlike Leibniz who
essentially restricts the notion of sufficient reason to
"contingent truths of fact", Wolff considers the notion to
have a much broader scope of application to include the set of all
possible objects and what Leibniz calls "necessary truths of
reason". The idea that everything has a sufficient reason is
presented formally by Wolff as the principle of sufficient reason.



Wolff's most extensive treatment of the *PSR* appears in
SSSS56-78 of his *Ontologia*. In this discussion,
Wolff appears to give two separate accounts of the theoretical origin
of the principle. On the one hand, in SS70, Wolff provides a proof
(or derivation) of *PSR* from *PC* and the notions of
"something" and "nothing". And, on the other
hand, in SS74, Wolff claims *PSR* is a principle of the
human mind and a self-evident logical axiom. Although *prima
facie*, it is unclear why Wolff attempts to advance both views, it
is perhaps worth pointing out the difference between (1) being able to
be demonstrate the truth of a proposition and (2) knowing the truth of
a proposition because it is self-evident. While demonstrating the
truth of a proposition yields knowledge of it, to know a proposition
because it is self-evident may or may not mean the proposition is also
demonstrable. There is no inconsistency, for example, in holding that
one and same proposition is both self-evident and demonstrable. A
proposition could be known immediately one way and yet, in another
way, follow as a conclusion of a sound deductive argument.



Wolff believes that the fact that *PSR* obtains becomes
apparent when we consider three specific aspects of our
rational/conscious experience. The first is that *PSR* is never
contradicted by experience; the second is that we can recognize
singular instances, or examples, of it in our experience of the world,
and the third is that we have an inquisitive attitude toward our
surroundings and future life (Ont. SSSS72-4). For Wolff,
these characteristics are not regarded as empirical evidence for
*PSR*, but rather that *PSR* is a necessary
presupposition for these characteristics to be a part of our conscious
experience. Thus by simply reflecting on the nature of our
understanding of the world, Wolff believes that we arrive at the
manifest truth of *PSR*.



Now according to Wolff there are at least four self-evident
(axiomatic) principles of human thought: *PC*, the principle of
excluded middle, the principle of certitude (or principle of
identity), and *PSR* (Ont. SSSS52-55). Of these,
only *PC* is indemonstrable in the sense that the truth of the
principle cannot be proved to follow from a formal deductive
inference. As we have seen, Wolff believes that we gain assurance of
the truth of this principle by attending to the psychological
experience of not being able to both affirm and deny our own existence
in introspection. Thus only in a weak (and non-Wolffian) sense of
"demonstration" can Wolff be said to demonstrate the truth
of *PC*. The remaining principles, however, are demonstrable in
the strict sense and each, he believes, can be derived from
*PC*. His demonstration of *PSR* in SS70 of the
*Ontologia* is as follows:



> 
> 
> Nothing exists without a sufficient reason for why it exists rather
> than does not exist. That is, if something is posited to exist,
> something must also be posited that explains why the first thing
> exists rather than does not exist. For either (i) nothing exists
> without a sufficient reason for why it exists rather than does not
> exist, or else (ii) something can exist without a sufficient reason
> for why it exists rather than does not exist (SS53). Let us assume
> that some *A* exists without a sufficient reason for why it
> exists rather than does not exist. (SS56) *Therefore nothing is
> to be posited that explains why A exists. What is more, A is admitted
> to exist because nothing is assumed to exist*: since this is
> absurd (SS69), nothing exists without a sufficient reason; and if
> something is posited to exist, something else must be assumed that
> explains why that thing exists.
> 
> 
> 



The crucial premise (italicized above) purports to reveal a
contradiction that follows from the assumption that something exists
without a sufficient reason. Since "nothing" cannot both
be something and nothing at the same time (according to *PC*),
the conclusion (or *PSR*) is claimed to follow. This proof was
the subject of an incisive critique by Wolff's contemporary and
critic, Christian August Crusius (1715-75), who (among other
things) accuses Wolff of an equivocation with the term
"nothing", and once the two different meanings of this
term are identified (*viz*. nothing as the opposite of
something, on one hand, and nothing as a non-being, on the other), the
supposed contradiction, purported to follow from the assumption,
cannot be established (Crusius 1741).



In any case, for Wolff, the expression "to provide the reason of
something" can be taken in two different ways. On the one hand,
if the something for which a reason is provided is regarded solely as
a possible thing, then "reason" stands to account for why
that thing (as a possible thing) is the possible thing that it is.
According to Wolff, every being is endowed with an essential nature.
Possible things have natures insofar as they as are comprised of a
number of non-contradictory determinations or predicates. Different
sets of determinations, and the relationships among these
determinations, serve as the principle of individualization within the
realm of possible things. Hence, to provide the reason for a possible
thing is simply to enumerate the determinations that make that thing
the kind of possible thing that it is. A reason, in this sense, is
regarded by Wolff as *ratio essendi* or the "reason of
being".



If, on the other hand, the something to which a reason is provided is
an actual (i.e., existing) thing, then "reason" stands to
explain why that thing as an actual thing comes into existence.
Reason, in this sense, is regarded as *ratio fiendi* or the
"reason of becoming". Recall that for Wolff existence is
simply a predicate or determination of possible things. A familiar
expression appearing in Wolff's writings is that existence is
"the complement of possibility" (Ont. SS174). The
basic idea here is that existence, as a predicate, perfects a possible
thing by making it actual and a "real individual". Real
individuals differ from nominal beings insofar as the former are
"complete and determinate". To be "complete and
determinate", in Wolff's sense of the expression, means
that every aspect or determination of a thing can be specified and
that its determinations are sufficient to individuate it from all
other things. Nominal beings, although "complete", are
indeterminate (cf. GL: c. 1, SS15). That is to say, although there
is a certain set of specifiable determinations that is sufficient to
pick out a given possible thing among all possible things, the total
set of its determinations is not specifiable. A being, in the most
general sense, is comprised of three different types of
determinations: *essentialia*, attributes, and modes. Essential
determinations define the essential nature of a being and a
being's attributes follow from, or are determined by, its
*essentialia*. Whereas *essentialia* and attributes are
both necessary properties of a thing, modes are contingent or
accidental properties. Thus to say a nominal being is indeterminate is
to say that there are modes of it that may or may not be present. In
the weakest sense, since existence is a mode, and nominal beings do
not exist (as such) but are able to come into existence under certain
conditions, all nominal beings are indeterminate.



Discerning the difference between the "reason of being"
and the "reason of becoming" is important for
understanding the different ways Wolff employs *PSR* in his
exposition of metaphysics. Depending on how exactly
"reason" is interpreted, the principle, "nothing is
without a sufficient reason for why it is rather than not" may
apply either to the realm of possibility or to the realm of actual
reality. Toward the end of his *Ontologia*, Wolff makes an
attempt to recognize formally two different versions of *PSR*
as "the Principle of Being" and "the Principle of
Becoming" respectively (Ont. SS866). As a Principle of
Being, *PSR* stands as a definition of a thing's
essential nature. Yet as a Principle of Becoming, *PSR* serves
to furnish the causes, or grounds, for why a real individual comes
into actuality.



It is on the basis of *PC* and *PSR* that Wolff proceeds
to explicate the fundamental concepts of his ontology. Recall that for
Wolff a being in the most general sense is any possible thing.
Possible things have essential natures insofar as they are composed of
a number of non-contradictory determinations or predicates. The
essence of any given possible thing is its principle of being, or
principle of individualization. Whereas the essence of a simple being
is defined by its essential properties, the essence of a composite
being is defined by the manner in which its parts are combined
together. In SS532 of his *Ontologia*, Wolff explains:



> 
> 
> A being is called composed which is made up of many parts distinct
> from each other. The parts of which a composite being is composed
> constitute a composite through the link which makes the many parts
> taken together a unit of a definite kind.
> 
> 
> 



In one respect, simple beings and composite beings are not simply two
different species of beings. It is not the case, for example, that
within the realm of all possible things simple beings exist separate
from, and in addition to, composite beings. More accurately, at the
nominal level of reality simples and composites result from an
epistemological distinction imposed by a perceiving mind in its
analysis of what "exists" (i.e., exists in a nominal
sense). Strictly speaking, the only substantial things to exist at any
level of reality are simple substances. Simples are defined by their
*essentialia*, and to borrow an expression from Gilson,
*essentialia* are both "compatible and prime"
(Gilson 1952: 114). That is to say, the essential properties that
define a given simple substance do not contradict one another, or
cancel each other out, and they are (themselves) not determined by any
other thing and/or property. In this light, Wolff's notion of
substance is perhaps best regarded as a notion of essence, where each
simple substance is a different set of compatible and prime essential
properties (see Burns 1966: 26 and Gilson, 1952: 115). Furthermore,
essential properties should not be viewed as the accidents of
substance because, according to Wolff, they are the substance itself.
In Wolff's system, the accidents of substance are the properties
that exist by virtue of a thing's *essentialia*. And
according to Wolff, there are three basic classes of accidents: proper
attributes, common attributes, and modes (Ont. SS148).



Proper and common attributes of substance follow from and are
determined by a thing's *essentialia*. Proper attributes
are the properties of a thing that are determined by all the
*essentialia* taken together, and common attributes are the
properties of a thing that are determined by only some, but not all,
its *essentialia*. Attributes (as such) are perhaps best
understood as necessary accidents, since they are determined by and
necessarily follow from a thing's *essentialia*. Modes,
in contrast, are only contingent accidents of substance. They are the
properties of a thing that may or may not be present, and if actually
present, they are causally the result of some contingent state of
affairs. More precisely, the possible presence of any given mode
follows from a substance's *essentialia*, but the actual
presence of a given mode is the result of something outside the
substance's essence that is causally responsible for its
presence in a being. At the nominal level of reality, composite beings
exist insofar as the accidents of a certain simple substance, or set
of simple substances, are linked and/or arranged together in a certain
sort of way. In SS789 of his *Ontologia*, Wolff writes:




> 
> 
> [t]he essence of a composite being consists only in mere accidents for
> the essence of a composite consists in the manner in which its parts
> are combined with one another.
> 
> 
> 


### 5.2 Cosmology



The notion of "extended-composite" lies at the heart of
Wolff's doctrine of the world-whole. Cosmology, as a special
metaphysical science, is the study of the world-whole in general. The
world, as such, is an extended composite of extended composites. In
SS544 of his *German Metaphysics*, Wolff explains:



> 
> 
> The world is a collection of mutable things that are next to each
> other, follow upon one another, but which are overall connected with
> one another.
> 
> 
> 



In precise terms, Wolff believes the world is an extended whole that
is composed of a finite number of interacting physical bodies. To
better understand the types of cosmological claims that Wolff defends
about the universe, it is perhaps helpful to consider first his
conception of physical bodies. Ultimately, the conclusions that Wolff
draws at the macroscopic level about the world-whole are simply
extrapolated from his analysis of physical bodies. After considering
Wolff's analysis of body, this section will conclude with an
overview of Wolff's view of space, time and material
extension.



Wolff's analysis of physical bodies is given from two different
perspectives. First is the "bottom-up" metaphysical
account of bodies, where bodies are defined as aggregates of simple
substances, and second is the "top-down" mechanistic
description, where the reality of bodies, given by the testimony of
the senses, is explained in terms of interacting primitive
*corpusula* (or corpuscles). To facilitate our discussion, we
should identify the three levels of description that Wolff employs
when giving his two perspective account. Identifying these three
different levels is helpful in understanding at what respective point
the mechanical and metaphysical accounts each terminate or bottom
out.



The ground floor (so to speak) is the atomic level that is occupied by
a "multitude" of simple substances. Unlike simple
substances at the nominal level of reality that lack the "mode
of existence", simples at the atomic level are real individuals
(i.e., complete and determinate, actually existing beings). In
addition to the term "simples", Wolff also refers to these
occupants of the atomic level as "elements" and
"atoms of nature" (*atomi naturae*). Atomic
elements (as such) are conceived by Wolff to be "unextended
points of force" that lack internal motion (*motus
intestinus*) but yet remain in a constant state of change. Each
atomic element is defined, or individuated, by its own distinctive
internal state and each is considered to be indivisible in-itself.
Although later Wolffians, such as Baumeister, would eventually refer
to Wolff's atomic elements as "monads", there is at
least one important respect in which Wolff's atomic elements are
different from Leibniz's monads (Baumeister 1747: 226). Leibniz
conceives monads as simple unextended substances, and hence Leibnizian
monads are "windowless" substances that do not interact or
influence one another. Wolff's atomic elements, in contrast, do
interact and have real dynamic influence over each
 other.[4]




The second level of description that Wolff employs when giving his
account of bodies is the microphysical level. The occupants of this
level are the primitive parts of bodies which Wolff calls corpuscles
or material atoms. In SS186 of his *Cosmologia*, Wolff
provides a helpful contrast between atoms of nature, on one hand, and
material atoms, on the other:



> 
> 
> That is called an atom of nature which is indivisible in itself
> because it is devoid of parts into which it can be divided. That is
> called a material atom which in itself is able to be divided, but for
> actually dividing it, existing causes in *rerum natura* are not
>  adequate.[5]
> 
> 
> 



Material atoms or corpuscles are indivisible in the sense that there
is nothing within the world that is capable of reducing them into
further parts. Corpuscles represent the lowest level of explanation
that is possible within a mechanical account of bodies. Similar to the
atomic level, the microphysical level lies beyond the boundaries of
human perception. Wolff believes that although corpuscles are
extended, fill space, and are endowed with the "force of
inertia", a precise statement of their size, magnitude, and
shape cannot be empirically determined. It is unclear, for example,
whether all corpuscles retain homogeneity with respect to their
magnitude and shape. Yet because corpuscles are a species of composite
beings, Wolff is confident that the essence of a corpuscle consists in
the manner in which its parts are joined together. A corpuscle is an
aggregate of atomic elements. Its component parts are simply the
unextended points of force that occupy the atomic level.



The third level of description that Wolff employs when giving his
account of bodies is the level of appearance or sensible reality. It
is at this level that bodies and their phenomenal properties, such as
extension, the force of inertia, and motor force (*vis
motrix*), are described in mechanistic terms. In SS793 of his
*Ontologia*, Wolff writes:



> 
> 
> I prefer that aggregates of simple substances, namely, those compound
> beings of which the material world is composed, be called bodies
> rather than simple substances...
> 
> 
> 



In a strict sense, a body is considered by Wolff to be a composite of
composites. The interacting atomic elements (conceived as unextended
points of force) give rise to primitive corpuscles and from the
cohesion of corpuscles, a body is thereby constituted at the level of
appearance. Wolff writes, " ... each body has its origin in
that which is not extended, although it is itself extended"
(*Cosmologia*, SS223). At the level of appearance, bodies
display a number of determinate properties. Each body has a
specifiable size or magnitude (i.e., it can be measured), it occupies
a fixed space or place (insofar as it is extended), it displays a
certain shape, and it is divisible to the primitive corpuscles from
which it is composed. Yet, according to Wolff, the properties of
bodies should not be considered as the accidents of anything
substantial because bodies are merely phenomenal manifestations of
real, interacting, atomic elements. Even the principal properties of
bodies used in the analysis of bodily change and motion (i.e., the
properties used in mechanics), such as extension, the force of
inertia, and motor force, are deemed by Wolff to be phenomenal
properties.



Now according to Wolff all sensible properties of bodies should be
considered as secondary (or mind-dependent) qualities. In SS144 of
his *Cosmologia*, Wolff writes: "...extension is a
phenomenon in the same sense in which color is accustomed to be called
a phenomenon...". And somewhat later in this same work, he
states in SS298: "[t]he force of inertia is called a
phenomenon in the same sense in which all sensible qualities are
called phenomena". Perhaps the best way to understand
Wolff's view of sensible properties is to consider a quick
comparison with Locke's corpuscularian view of bodies. For
Locke, the primary qualities of bodies, such as extension, solidity,
shape, size and texture give rise to the secondary qualities that we
perceive in bodies, such as color, sound, taste, smell and
temperature. According to Locke, secondary qualities are nothing in
the objects themselves but are the result of certain
"powers" inherent in the primary qualities of things which
effect various sensations in us, such as the sensation of a certain
color or temperature. Thus it is by virtue of a body's
micro-structure that we are able to perceive its secondary qualities.
Wolff, for the most part, accepts this causal-corpuscularian theory of
secondary qualities. However, unlike Locke, Wolff believes that all
sensible properties are secondary qualities that result from a
body's atomic structure. In very simplistic terms, sensible
properties are for Wolff what color, sound, taste, smell and
temperature are for Locke. For both philosophers, secondary qualities
are phenomenal and mind-dependent properties having their causal
origin in some objective (i.e., mind-independent) reality. For Locke,
this reality is the independently existing corpuscles that comprise
the material world; and for Wolff, this reality is the unextended
points of force, or simple substances, that occupy his atomic level
cf. Cosm. SS191).



Before explaining Wolff's view of how extended composites come
into being (i.e., the causal process that allows us to form our ideas
of extended objects), it is necessary to say a few prefatory words
about his view of space and time. The notions of "place"
and "space", on one hand, and the notion of
"time", on the other, figure in at different stages of
Wolff's exposition of extended reality.



First and foremost, there is an important distinction in Wolff's
cosmology between "general space" and "particular
space". Particular space (or a given place) is what an extended
body "fills" or "occupies" by virtue of its
corpuscular parts (Cosm. SSSS122-4). Its reality is
derivative of the interacting atomic elements that give rise to
individual corpuscles. For Wolff, a corpuscle's place simply
results from a corpuscle's extension. A given place is conceived
as an imaginary immobile container that has the same dimensions as the
extended thing that occupies it (Ont. SSSS676-9).
General space, in contrast, is conceived as the perceived order of
coexisting bodies. As explained above, the existence of bodies is
established by Wolff experientially and amounts to an instance of
historical cognition. In SS45 and SS46 of his *German
Metaphysics*, Wolff explains:



> 
> 
> If we pay attention to ourselves [as thinking things], we will find
> that we are conscious of many things outside ourselves. However, we
> set them apart from us in that we recognize that they are
> distinguishable from us, just in the same way as they are set beside
> each other, we recognize they are distinguishable from each
> other.... In that there are many things now which exist at the
> same time and which are presented apart (and yet at the same time
> different) from each other, such things come into being under a
> certain order. And as soon as we perceive this order we perceive
> space. Therefore, if we do not want to examine the matter differently
> than we recognize it, we must assume space is the order of such things
> which are simultaneous.
> 
> 
> 



Wolff's derivation of general space essentially involves three
steps. First, knowledge of the self, as a thinking thing, affords a
distinction between consciousness, on one hand, and consciousness of
external things, on the other. Second, since that which is conscious
(*viz.* the self) is different from that of which it is
conscious (*viz.* the world), the self can recognize the
historical and mathematical fact that it is conscious of many external
things at one time (i.e., the world as a plurality). And third, since
this empirical fact affords knowledge of real existences, the order or
way the self represents these things is what becomes known as space.
To borrow Kant's terminology, Wolffian space lacks
"objective reality" because it is simply abstracted from
the coexistence of things in the world, and therefore takes on purely
a subjective character (cf. Beck 1969: 270).



In contrast to his theories of place and general space, Wolff holds a
much more realistic theory of time. In a strict sense, place and space
serve an explanatory role for Wolff at two distinct levels of
description (*viz*. the micro-physical level and the level of
appearance). Since atomic elements are unextended, the concepts of
place and space are considered by Wolff to be extraneous at the atomic
level. Time, however, is not. Atomic elements are in time insofar as
each element is in a constant state of change. In his most general
description of time, Wolff writes: "[t]ime is the order of
successive things in a continuous series" (Ont. SS572).
Since each atomic element produces in-itself a constant and continuous
series of changes, time is regarded by Wolff as the objective measure
of such changes. One clear statement of the Wolffian view of the
relationship between time and change can be found in a letter to Kant
(dated 13 October 1770) from Johann Heinrich Lambert. Lambert
(1728-77) writes:



> 
> 
> All changes are bound to time and are inconceivable without time. If
> changes are real, then time is real, whatever it may be. If time is
> unreal, then no change can be real. I think, though, that even an
> idealist must grant at least that changes really exist and occur in
> his representations, for example, their beginning and ending. Thus
> time cannot be regarded as something unreal. It is not a substance,
> and so on, but a finite determination of duration, and like duration,
> it is somehow real in whatever this reality may consists (AA
> 10:107\*\*\*AA?\*).
> 
> 
> 



For Wolff, Lambert, and Moses Mendelssohn, time is real insofar as it
is an objective measure of change (cf. Falkenstein 1991 for
discussion). Change is a constant feature of existing reality in that
real individuals are finite and created beings with a determinate
duration. Real individuals come into and go out of existence. Time,
therefore, is applicable to the series of changes that occur within a
given individual and, in the same respect, it is applicable to the
totality of all the individuals that compose the world-whole. Thus for
Wolff there is a meaningful sense in which real individuals and the
world-whole (itself) are "in time". This is not to say,
however, that time is granted its own ontological existence. In
Lambert's words, time is not a substance (i.e., something real
in-and-of itself). More precisely, time is the measure of the
objective order of change that real things undergo.



Understanding the sense in which atomic elements are "in
time" is important for grasping the manner in which
Wolff's atomic elements interact. Since atomic elements lack
extension, the nature of atomic interaction is not spatial. It is not
the case, for example, that Wolff's simple substances influence
one another by physical contact and repulsion. Instead, atomic
elements as unextended points of force affect, and are responsive to,
degrees of change by communicating with each other in time. The series
of changes internal to a given atomic element are the result of its
own power (or motor force) as well as the motor forces of other
elements to which it is connected. Ultimately Wolff believes that it
is the interacting forces of a multitude of simple substances that
gives rise to our idea of an extended object. In particular, we
perceive extended objects at the level of appearance insofar as there
are unextended points of force interacting in time at the atomic
level. Our confused perception of this temporal interaction results in
the idea of an extended object. Similarly to Locke, Wolff believes
that it is the primitive qualities of a composite that produce, or
effect in us, the various ideas we have of its secondary qualities.
Since all sensible properties are considered by Wolff to be secondary
qualities, extension, or a composite's extendedness, results
from the primitive forces of a composite at the atomic level. The
analogy that Wolff presents to help explain the phenomenal
manifestation of extension involves a rapidly ringing bell (Cosm.
SS789; cf. Burns 1966: 52). According to Wolff, just as the
impression we gain from a rapidly ringing bell is the sound of one
prolonged peal, where the successive strikes of a bell's clacker
are perceived as one monomial sound, our impression of extension is
likewise the result of many successively acting atomic forces that
give rise to our confused perception of one continuous extended
object.



The notion of "extended-composite", as already mentioned,
is what ultimately stands at the heart of Wolff's doctrine of
the world-whole. Insofar as the world is a composite being, it follows
from the principles of Wolff's ontology that the world's
essence consists in the manner in which its parts are linked together.
The world's parts, as described from the standpoint of
appearance, are simply the multitude of interacting physical bodies
that are perceived in everyday life. And, if described from a
metaphysical standpoint, the world's parts are conceived by
Wolff to be the interacting unextended points of force that occupy his
atomic level. Yet regardless of what standpoint or level of
description is employed, it is clear that a necessary condition of the
world's existence is that its parts need to be interconnected.
According to Wolff, the world is conceived as a substantial whole
(*totum substantiale*) by virtue of the fact that all of its
parts form real reciprocal connections with one another. On the basis
of this "interconnection-thesis" the world is defined
formally by Wolff as "a whole which is not also a
part".


### 5.3 Psychology (Empirical and Rational)



While the soul, as a simple substance, is understood to be a part of
the world, and so is implicated in the treatment of cosmology, this
does not exhaust what can be known of it, a fact that leads Wolff to
treat it as a separate topic of metaphysics. Indeed, Wolff's
psychology constitutes one of his signal and most historically
influential innovations. Most generally, insofar as Wolff seeks to
offer a scientific account of the *human* soul specifically,
and indeed with a focus on its cognitive and conative functions, his
psychology represents a significant, and distinctly modern, departure
from both the treatment of the soul in the context of a generic
science of living things, still prevalent among Aristotelian natural
philosophers in seventeenth century Germany, and from the metaphysical
treatment of the soul in the context of a pneumatology, or doctrine of
finite *and* infinite spirit (Stiening 2003, Vidal 2011). More
narrowly, Wolff's principal, and best-known innovation in
psychology consists in his clear separation between two distinct
investigations of the soul, the first based on the observation of
one's own mind, identified as *empirical psychology*, and
the second which seeks to use reasoning to uncover truths about the
soul that are not readily disclosed by experience, identified as
*rational psychology*.



Wolff's distinction between empirical and rational psychology
proved to be enormously consequential, but no less important (if less
well attended to) is the fact that these disciplines remain
intrinsically connected. For Wolff, the observations catalogued in the
course of empirical psychology serve as principles for the inferences
of rational psychology, and the resulting findings on the part of
rational psychology serve to guide our empirical observation in search
of confirmation. Thus, Wolff writes, that which everyone can
experience of themselves will serve "as a principle for deriving
something else that not everyone can immediately see for
themselves" (GM: SS191), and that which is known of the soul
from experience "is the touchstone [*Probier-Stein*] of
that which is taught [in rational psychology] of its nature and
essence" (GM: SS727). Rather than constituting distinct
disciplines, empirical and rational psychology amount to complementary
parts of a *single* science, working together in the same way
in which observation and theory co-operate in astronomy (EP: SS5).
Consequently, Wolff's rational psychology is not to be
identified as a narrowly *rationalistic* psychology, insofar as
the latter is taken to intend a science of the soul that proceeds
*completely* independently of experience. Nor is this
interdependence of the two parts of psychology an aberration as Wolff
takes their union as exemplifying his ideal for science of a
*connubium rationis et experientiae* (EP: SS497; cf., Dyck
2014, Rumore 2018).



Turning first to empirical psychology, Wolff's treatment can be
divided into four parts: (1) the initial consideration of the human
soul in an attempt to arrive at an initial definition; the
consideration of the soul's (2) cognitive faculty and (3)
appetitive faculty; and (4) a consideration of what can be known of
the soul's relation to the body through experience. In the first
part, Wolff begins, in Cartesian fashion, by first considering the
grounds for our certainty in the existence of the soul (EP:
SS11-14). Wolff begins by asserting that we are conscious of
ourselves and other things, which he takes to be confirmed by our own
indubitable experience (for to doubt it would presuppose such
consciousness), and inasmuch as anything that is so conscious must
exist, a claim Wolff identifies as an identical proposition or axiom
(cf. GL: c. 3, SS13), it follows that we can be certain that we
exist. Wolff conveniently reconstructs this as a syllogism:



> 
> * Whatever being is conscious of its self and of other things
> outside of it, exists.
> * We are actually conscious of ourselves and of things outside of
> us.
> * Therefore, we exist. (EP: SS16)
> 
> 
> 



In addition to assuring ourselves of the indubitability of the
knowledge of our own existence (cf. Euler 2003), this initial
consideration supplies a touchstone for what will count as
demonstratively certain, but also provides the elements for a nominal
definition of the soul. Thus, the soul is identified just as
"that being in us which is conscious of itself and other things
outside of it" (EP: SS20) which, as an existing thing, can
serve as the object of empirical psychology.



The next task for empirical psychology consists in cataloguing the
various capacities that the soul has, which Wolff brings under two
general headings: the cognitive faculty (*facultas
cognoscendi*) and the appetitive faculty (*facultas
appetendi*). Relevant to the distinction between (sub-)faculties
in both cases is the distinction, borrowed from Leibniz, between
obscure and clear perception (where the latter but not the former
suffices for recognition of the perceived thing), and (clear but)
confused and (clear and) distinct perception (where the latter but not
the former involves the ability to explicate what serves to
distinguish the perceived thing from others). Accordingly, both the
cognitive and appetitive faculty are distinguished into lower and
higher parts, where the lower includes capacities relating to ideas
and notions that are obscure or clear but confused, and the higher
those relating to ideas and notions that are distinct (EP:
SSSS54-5, 584). (It bears noting that Wolff also
distinguishes between obscure and clear perceptions inasmuch as the
former are not *apperceived* but the latter are; cf. EP:
SSSS25, 35; RP: SS20, and for discussion see Wunderlich
2005 and Thiel 2011).



Among the faculties Wolff considers within the lower cognitive faculty
are the faculty of sense, imagination, the fictive faculty, and
memory. Sense, which includes the five sensory modalities, is
understood as the capacity for sensations, where these are perceptions
the reason for which is contained in the organs of our bodies, given
the presence of an external thing (EP: SSSS67, 65).
Imagination, by contrast, is the faculty for producing perceptions in
the absence of sensible things. Wolff further claims that the
imagination's activity is guided by a general (associative) law
that, when we have perceived things together (as parts of a whole, for
instance, or as contiguous in space), if the perception of one is
produced, then the imagination supplies the perception of the other
(EP: SS117). It is the imagination that is likewise responsible
for the order of ideas in dreams. The fictive faculty (*facultas
fingendi*) is our capacity to combine or divide the products of
the imagination to create new representations (SS144), and memory
is defined as the faculty through which we *recognize*
reproduced ideas as previously had (SS175).



Where the lower cognitive faculty handles the generation and
(re)production of obscure and confused ideas, the higher cognitive
faculty encompasses the capacities and operations through which we
introduce clarity and distinctness into those ideas. Accordingly,
Wolff first considers the faculties of attention, whereby we introduce
more clarity into a part of a composite perception (EP: SS237),
and reflection, through which we successively direct attention to what
we perceive (as well as, in a Lockian vein, to the soul and its
operations--SS261) and thereby make distinct perception
possible (SS266). The capacity for distinct representation in
general is identified as the understanding, which can be pure or
non-pure depending on whether it admits confused representations,
though since these are unavoidable in the case of the human being, our
understanding is never pure (EP: SSSS313-4; for general
discussion see Chance 2018). With an eye to his discussion of logic, Wolff further
distinguishes three operations of the intellect with respect to its
cognitions: simple apprehension (through which notions or
representations of what is common to multiple things are formed),
judgment (through which agreement or disagreement between
representations is asserted), and discursion or reasoning (where
judgments are formed on the basis of previous judgments) (EP:
SSSS325, 366-7; cf. Dyck 2016, Rumore 2018). This latter
operation informs Wolff's definition of the *faculty* of
reason as the capacity to perceive the interconnection among universal
truths (SS483), though Wolff again emphasizes that our reason is
never pure but is always to some extent reliant upon
*experience* (SSSS495-7).



Where the discussion of the cognitive faculty is relevant to
Wolff's aims in logic and metaphysics, the treatment of the
appetitive faculty in empirical psychology is significant for
Wolff's practical philosophy. Wolff likewise distinguishes the
appetitive faculty into lower and higher parts, where the distinction
turns on whether there is an obscure or confused cognition of the good
or evil (grounding a sensory desire or aversion), or a distinct
cognition of the good or evil (grounding our act of willing or not
willing). In connection with the latter, Wolff takes up the issue of
freedom. He rejects the conception of freedom in terms of a capacity
to act contrary to determining motives as counter to our experience
and to the principle of sufficient reason (EP: SS944), and instead
defends a (Leibnizian) compatibilist conception, in accordance with
which a freely willed act involves a distinct cognition of the
perfection of some thing (which generates a motive to act in its
favor); is spontaneous, or has its reason within the agent (insofar as
the agent chooses it because it is pleasing); and is contingent, or
the agent is not determined to choose it through its essence (EP:
SSSS933-41; cf. Kawamura 1996; Dyck forthcoming[a]).



Lastly, but importantly, empirical psychology takes up the
distinctively early modern problem of what can be experienced of the
soul's relation to the body. Here Wolff notes that we experience
that some states of the soul depend upon the body (such as
sensations), and some states of the body depend upon the soul (such as
voluntary actions), such that the body and soul stand in a union or
*commercium*. Nonetheless, Wolff contends (following
Malebranche and in anticipation of Hume) that we have no experience of
the causal power through which the soul influences the body and vice
versa, but rather that our experience only confirms the general
agreement between the states of each without penetrating to its ground
(EP: SSSS961-2).



In turning to the rational consideration of the soul, Wolff's
aim is not to determine what can be known completely independently of
experience but rather to employ what has been discerned in empirical
psychology as principles from which its demonstrations proceed and as
cognitions for which reasons are to be given (RP:
SSSS3-4; Richards 1980). Conforming to this, the topics
of rational psychology proceed from those which are closest to and
draw most heavily from empirical psychology, such as the account of
our soul's nature and essence, to the increasingly more
speculative topics, such as the defense of the pre-established harmony
to the demonstration of the soul's immortality and consideration
of its state after death.



The determination of the soul's nature and essence sets out from
the definition of the soul given in empirical psychology as that in us
which is conscious of itself and other things. Wolff argues that this
consciousness is the result of a complex activity that involves
reflection on and comparison of parts of a given perception as well as
attention and memory (RP: SSSS22-3, 25). Given this,
Wolff contends, the soul must be distinct from body since such an act
cannot be explained in terms of a change in figure, magnitude, or the
location of parts, through which alone changes in body are possible.
Similar considerations serve to show that no composite can think, and
thus that the soul, as conscious, must not be composite and is
therefore simple, and indeed, a simple substance, since it perdures
through changes in its thoughts (RP: SSSS44, 47-8). That
the soul is a substance further implies for Wolff (as it did for
Leibniz) that it is endowed with a power, understood as a sufficient
reason for the actuality of the states that are possible for it
through its faculties (RP: SSSS54-5; cf. Blackwell 1961,
Hessbruggen-Walter 2004). Wolff proceeds to determine the
character of this power (which must be a single one given the
soul's simplicity), and he concludes that, because sensations
are representations of the world in accordance with the position of
the organic body, and because all of the representations the soul is
capable of are derived from sensations, it follows that the
soul's power is just a power of representing the world in
accordance with the position of the body, which power Wolff finally
identifies as the essence and nature of the soul (RP:
SSSS64-9).



Rational psychology also takes up the question of what best explains
the agreement between the states of the soul and the body. Wolff
considers three possible systems that purport to explain this
agreement: (i) the system of physical influx, according to which one
substance produces a state in another directly through its own
activity (RP: SSSS558-60), (ii) the (Cartesian) system
of occasional causes, according to which God modifies one substance on
the occasion of some state arising in another
(SSSS589-91); and (iii) the (Leibnizian) system of
pre-established harmony, where the agreement between states of
substances is the result of God's initial activity in
actualizing this world of substances (SSSS612-13). Wolff
provides a number of familiar objections to the first two systems,
claiming for instance, that physical influx conflicts with the laws of
physics (cf. SSSS578-9), and that occasionalism relies
on what amounts to a perpetual miracle (cf. SS603), while
defending the pre-established harmony from similar criticisms (cf.
Watkins 2005: 45-51). Even so, given that any possible
explanation cannot be confirmed or rejected by experience (as was
disclosed at the conclusion of empirical psychology), each of these
systems amounts to a mere *hypothesis*, and Wolff's
conclusion is only that the pre-established harmony is a more
*probable* hypothesis than the other two (RP: SSSS503,
685; cf. Dyck 2014: 34-6), though he thinks that nothing
significant turns on settling this contentious issue.



The last major topic Wolff turns to is the most speculative, namely,
the demonstration of the soul's immortality of the soul and its
state after death. Immortality is taken to presuppose the
incorruptibility of the soul, that is, that the soul does not
naturally pass away after the death of the body, but (contrary to the
Cartesians) Wolff does not think that this is all that is involved as
any immortality worth having (and that would be consistent with
Scripture) must also extend to the preservation of the soul's
capacity for distinct perception (that is, its spirituality) and its
consciousness that it is the same being in the afterlife as it was
before the body's death (or its *personality*). The
soul's incorruptibility follows straightforwardly from the fact
that it is simple (and so incapable of decomposition); inductive
grounds are offered in favor of the soul's preservation of its
spirituality (namely, that the clarity of the soul's perceptions
is enhanced in all "great changes"--RP: SS745);
and the soul's maintenance of its personality is shown by
reference to the law of imagination in accordance with which its
subsequent perceptions will lead it to recall previous ones. The
relative merits of these arguments were hotly debated, with especially
notable contributions by Wolff's colleague in Halle, G. F.
Meier, and later by Mendelssohn (in his famous *Phaedo*), and
ultimately Kant (for discussion, see Sassen 2008; Dyck 2014:
141-72).


### 5.4 Natural Theology



Wolff's treatment of metaphysics concludes with a consideration
of natural theology defined as "the science of those things that
are possible through God" (NT: I, SS1, see Corr 1973). Yet, at the same
time, natural theology also provides a bottom-up justification for
metaphysics insofar as metaphysics is concerned with actual existing
beings of a contingent, and so created, reality. Wolff indicates that
natural theology has two principle aims: (1) to prove the existence of
God and (2) to determine what pertains to the essence and attributes
of God, and what follows from these.



Concerning the demonstration of God's existence, Wolff had
offered criticisms (much to the chagrin of his Pietist opponents) of a
variety of traditional proofs early in his career (cf. Theis 2018:
221-3). In his *Natural Theology*, however, Wolff
presents and defends two proofs: an *a posteriori* proof
presented at the outset of the first volume, and an *a priori*
proof provided at the beginning of the second. Wolff's *a
posteriori* proof sets out from the fact (elaborated at the outset
of empirical psychology) that we exist, and proceeds to argue that the
reason for our existence must be found in a necessary being:



> 
> 
> The human soul exists or we exist. Since nothing is without a
> sufficient reason why it is rather than is not, a sufficient reason
> must be given why our soul exists, or why we exist. Now this reason is
> contained in ourselves or in some other being diverse from us. But if
> you maintain that we have the reason of our existence in a being
> which, in turn, has the reason of its existence in another, you will
> not arrive at the sufficient reason unless you come to a halt at some
> being which does have the sufficient reason of its own existence in
> itself. Therefore, either we ourselves are the necessary being, or
> there is given a necessary being other and diverse from us.
> Consequently, a necessary being exists (NT: I, SS24).
> 
> 
> 



From there, Wolff argues that the necessary being must also be
independent, or have its sufficient reason in itself, and cannot have
a beginning or end in time or is eternal. As such, the necessary being
cannot be identified with the world (which is composite) or anything
within it (since these have a beginning and end); moreover, it cannot
be identified with the soul since unlike the soul it does not depend
on the world. Therefore, the necessary being is identified as God,
understood as an independent being in which the reason for the
actuality of the world and the soul is found (NT: I, SS67, see Corr 1973).



By contrast, Wolff's *a priori* proof for God's
existence proceeds from the identification of God as the most perfect
being (*ens perfectissimum*):



> 
> 
> God contains all compossible realities in the absolutely highest
> degree. But He is possible. Wherefore, since the possible can exist,
> existence can belong to it. Consequently, since existence is a
> reality, and since realities are compossible which can belong to a
> being, existence is in the class of compossible realities. Moreover,
> necessary existence is the absolutely highest degree. Therefore,
> necessary existence belongs to God or, what is the same, God
> necessarily exists (NT: II, SS21, see Corr 1973).
> 
> 
> 



From the notion of a most perfect being, Wolff purports to prove God
is an *ens realissimum* (or most real existing being). However,
like Leibniz before him commenting on the Cartesian ontological proof,
Wolff believes God must first be shown to be possible in order to be
shown to exist. According to Wolff, arriving at the knowledge of God
as an *ens perfectissimum* involves first contemplating the
attributes that are present in the human soul, to a limited degree,
and then extrapolating those attributes as unlimited qualities to God.
Things are compossible insofar as they can coexist in the same
subject. Since existence is a mode or reality for Wolff, existence is
considered to fall within the class of compossible realities. And just
as it is better to exist than not to exist, it is better to exist
necessarily than just to exist contingently, therefore Wolff concludes
that God's existence is necessary.



With God's existence assured, Wolff considers what can be known
of Him. God is taken to have an understanding, consisting in His
distinct representation of all possible worlds and which
representation itself originates from the divine essence (NT: II,
SSSS81, 84). God is also shown to have a will, through which
He chooses one possible world to make actual, and since God's
choice in doing so finds its sufficient reason in his distinct
cognition of the supreme perfection of that world, Wolff identifies
God's will as *free* (in the same sense of freedom
presented in the empirical psychology, albeit in the highest possible
degree--NT: II, SS277). Wolff additionally considers
God's *wisdom*, which consists in His choice of the
appropriate means to realize His end in creation, namely, the
manifestation of His own glory and perfection (NT: I, SS629), and
*goodness*, which consists in His conferring of as much
goodness on creatures as is consistent with His wisdom (NT: I,
SSSS697-9).



While these discussions conclude the proper subject matter of natural
theology, in the second half of the second volume Wolff additionally
turns to critically examining various systems of atheism and radical
thought. Significantly, among the views discussed is
*Spinozism*, and indeed his treatment is considerably detailed
(spanning SSSS671-716 of the second volume), likely
reflecting the fact that Wolff had himself faced a persistent
accusation of supporting Spinoza on the part of his Pietist critics.
In contrast, however, with other discussions of Spinoza by
philosophers of this period, Wolff's does not trade in
convenient caricatures or speculation concerning the real (immoral)
motives behind Spinoza's thought but hews closely, if
critically, to the text of the *Ethics*. Wolff scrutinizes
Spinoza's definitions, particularly of God, substance,
attribute, mode, and finite thing (which he contrasts with their
proper definitions in the Leibnizian-Wolffian philosophy), and
proceeds to show how these figure into Spinoza's account of
extension (NT: II, SSSS688-93), doctrine of bodies
(SSSS694-6), claims of the uniqueness and necessary
existence of substance (SSSS697-706), and his faulty
account of infinite thought as composed of an infinite number of
finite thinking things (SSSS707-8). Wolff's
discussion proved rather influential, with Mendelssohn echoing and
developing it, and the accuracy of Wolff's characterization of
Spinoza was also a point of discussion in the famous
*Pantheismusstreit* (cf. Beiser 1987: 103).


## 6. Practical Philosophy



The subject matter of Wolff's practical philosophy is restricted
to those things that have to do with human action. In Wolff's
Latin texts, practical philosophy is divided into four main
disciplines: universal practical philosophy, natural law, politics,
and moral philosophy. And just as ontology purportedly provides the
foundational underpinnings for the disciplines of "special
metaphysics" in the theoretical realm, universal practical
philosophy plays an analogous role for the disciplines of natural law,
politics, and moral philosophy in the practical realm.



A central and perhaps unifying concept in Wolff's practical
writings is the concept of "perfection". In an early
letter to Leibniz, dated 4 May 1715, Wolff explains the importance
that the concept serves in his ethics:



> 
> 
> I need the notion of perfection for dealing with morals. For, when I
> see that some actions tend toward our perfection and that of others,
> while others tend toward our imperfection and that of others, the
> sensation of perfection excites a certain pleasure [*voluptas*]
> and the sensation of imperfection a certain displeasure
> [*nausea*]. And the emotions [*affectus*], by virtue of
> which the mind is, in the end, inclined or disinclined, are
> modifications of this pleasure and displeasure; I explain the origin
> of natural obligation in this way... From this also comes the
> general rule or law of nature that our actions ought to be directed
> toward the highest perfection of ourselves and others. (Leibniz 1989a:
> 231-232)
> 
> 
> 



According to Wolff, the ultimate goal of human action is to attain, or
at least approximate, the highest degree of perfection that is
possible. Humans, as individuals or groups, should strive for
perfection insofar as moral worth and goodness reside in the objective
essence of humankind. In a strict sense, each person is obligated by
the law of nature to instantiate perfection in his/her own life.
Actions that tend toward perfection produce pleasure and actions that
tend toward imperfection produce displeasure (or pain). In many
respects, this consequentialist feature of Wolff's ethical
theory resembles various forms of utilitarianism that were emerging in
England during the mid-to-late eighteenth century.



Also central to Wolff's practical philosophy is its autonomy
from theological doctrine. Although maintaining that a universal
ethics is certainly compatible with the teachings of Sacred Scripture,
Wolff is adamant that morality does not depend on revelation or
God's divine commands. Advocating the separation of philosophy
and religion is a theme that Wolff developed and defended throughout
his entire career and it is a feature of his thought that secures him
a place among other philosophers of Europe's Enlightenment.


## 7. Other Philosophical Contributions



Wolff's prominence in eighteenth-century Germany, and his
wide-ranging interests, have meant that he is an important figure in
the history of a number of established fields in the eighteenth
century, including mathematics, physics, political theory, and even
economics. Wolff also made notable, even pioneering contributions to
disciplines that were not as yet recognized as distinct areas of
philosophical inquiry. Wolff had, for instance, an early interest in
the philosophy of language, having devoted a dissertation to the topic
in 1703 (*Disquisitio philosophica de loquela*), an interest he
continued to pursue in subsequent discussions in his logical writings,
relating to semiotics and hermeneutics, and in his psychological
texts, concerning the relation between mental and linguistic entities
(see Favaretti Camposampiero 2018 for details). Wolff is also widely
recognized as a founding figure in the discipline of
aesthetics--while his only text devoted to the topic is a
treatise on civil architecture (a volume in a mathematical textbook),
Wolff's account of aesthetic pleasure in terms of the intuitive
cognition of perfection (EP: SS511), and identification of that
perfection as consisting in a unity in multiplicity, were taken up and
discussed by later aesthetic theorists, including A. G. Baumgarten
(the father of modern aesthetics), J. C. Gottsched, J. G. Sulzer
(1720-79), and Mendelssohn (see Beiser 2009; Buchenau 2013).