## 1. Orientation




The theory of divine illumination is generally conceived of as
distinctively Christian, distinctively medieval, and distinctively
Augustinian. There is some justification for this, of course, inasmuch
as Christian medieval philosophers gave the theory serious and
sustained discussion, and inasmuch as Augustine gave illumination a
very prominent role in his theory of knowledge. Still, it is better to
think of the theory in a wider context. Divine illumination played a
prominent part in ancient Greek philosophy, in the later Greek
commentary tradition, in neo-Platonism, and in medieval Islamic
philosophy. Moreover, it was Christian medieval philosophers, near the
end of the thirteenth century, who were ultimately responsible for
decisively refuting the theory. I will suggest that we view this last
development as the first great turning point in the history of
cognitive theory.




I understand a theory of divine illumination to be a theory on which
the human mind regularly relies on some kind of special supernatural
assistance in order to complete (some part of) its ordinary cognitive
activity. The assistance must be *supernatural*, of course, or
it will not count as *divine* illumination. It must be
*special*, in the sense that it must be something more than the
divine creation and ongoing conservation of the human mind. (If this
by itself were to count as illumination, then all theists would be
committed to the theory of divine illumination.) The mind must
*regularly* rely on this assistance, in order to complete its
*ordinary* cognitive activity: otherwise, an occasional mystical
experience might suffice to confirm a theory of divine illumination.
But a defender of the theory need hold only that we require this
assistance for *some part of* our ordinary cognitive activities:
hardly anyone has supposed that every form of human cognition requires
divine illumination.




It is useful to think of divine illumination as analogous to grace.
Just as a proponent of grace postulates a special divine role on the
volitional side, so a proponent of divine illumination postulates a
special divine role on the cognitive side. Grace is intended as an
explanation not of all human desires and motivations, nor even of all
virtuous desires and motivations. Rather, the proponent of grace holds
that there is a certain class of volitional states, crucial to human
well-being, that we can achieve only with special divine assistance.
Likewise, the theory of divine illumination is intended as an
explanation not of all belief, nor even of all knowledge. Rather, the
theory holds that there are certain kinds of knowledge, crucial to
cognitive development, that we can achieve only with special divine
assistance. It is an odd fact that, despite the close analogy, grace is
regarded not as a philosophical question, but as a theological one. It
is an equally odd fact that, whereas divine illumination hasn't
generally been regarded as plausible since the thirteenth century,
grace continues to be taken seriously by many theologians. Perhaps both
of these facts can be accounted for by motivational psychology's
relative obscurity in comparison to cognitive psychology.




For most people today it is hard to take divine illumination
seriously, hard to view it as anything other than a quaint relic. A
first step toward developing a proper perspective on the theory is to
see it in its broader context, not as peculiarly Christian or
medieval, but as an assumption shared by most premodern
philosophers. A second step in the same direction is to identify and
to take seriously the philosophical problem that drives illumination
theory. In large part, the theory has been invoked to explain rational
insight -- that is, a priori knowledge. For much of the modern era,
philosophers have been preoccupied with empirical knowledge and have
not had much interest in this topic. (Recently, this situation has
changed notably; for foundational recent treatments, see Bealer 2000
and Bonjour 1998.) To see how something like divine illumination could
have ever seemed at all plausible, one has to see how deeply puzzling
the phenomenon of rational insight actually is. One way of seeing
this, and of seeing how little we understand rational insight, is to
look at cases where something goes wrong. A recent biography of the
Nobel-prize winning mathematician John Nash describes his long period
of mental illness, during which time he held various odd beliefs such
as that extraterrestrials were recruiting him to save the world. How
could he believe this, a friend asked during a hospital visit, given
his devotion to reason and logic?



> "Because," Nash said slowly in his soft, reasonable
> southern drawl, as if talking to himself, "the ideas I had about
> supernatural beings came to me the same way that my mathematical ideas
> did. So I took them seriously" (Nasar 1998, p.11).




In a case such as this we don't know what to do, because we are
accustomed to give unhesitating trust to the deliverances of pure
reason. But why should we trust reason in this way? Why should we have
confidence that others can come to share our insights? Where does it
come from? The theory of divine illumination attempts to answer such
questions. 


## 2. The Ancient Background




What follows is by no means a comprehensive survey. Still, it seems
useful to begin near the beginning, with this remark by Socrates from
the *Apology*: 



> I have a divine or spiritual sign which Meletus has
> ridiculed in his deposition. This began when I was a child. It is a
> voice, and whenever it speaks it turns me away from something I am
> about to do, but it never encourages me to do anything (31d, tr.
> Grube).




This appears to be an entirely straightforward expression of a theory
of divine illumination. It is not clear who is providing the
illumination. Apuleius (fl. 150 CE) would later identify the source as
a certain kind of friendly demon, and argue that it was only fitting
for Socrates, the most perfect of all human beings, to receive such
illumination (*De deo Socratis*, XVII-XIX). (This idea that
illumination comes to those who deserve it would be proposed by
Augustine as well [e.g., *De magistro* 11.38], but abandoned in
his later writings as untenable.) As one might expect from Socrates,
his illumination seems restricted to the moral sphere. Its form is
unclear: is it propositional? (see *Phaedrus* 242bc) Is it
merely the pang of conscience? (For discussion of these and other
questions, see e.g. the papers collected in Destree and Smith
2005.) Whatever the details, Socrates is explicitly describing a kind
of cognitive guidance that has a "divine or spiritual" source. The
passage may be an embarrassment to classicists, but it surely belongs
in the same tradition as later medieval endorsements of
illumination. 




Not all appeals to the divine involve this sort of direct
communication. (Indeed, Socrates's reference to a "voice" is quite
extraordinary.) But the leading figures in ancient Greek philosophy
were equally committed to some kind of divine role in cognition.
Plato's theory of recollection presupposes that the human mind somehow
has built into it a grasp of the Forms, suggesting that at some point
the soul must have received some kind of illumination. Indeed, Plato's
arguments for recollection anticipate the two lines along which
medieval views would later develop. The *Meno* focuses on a
priori, rational insight, as illustrated by the slave's ability to see
for himself the validity of a geometrical proof. The *Phaedo* in
contrast focuses on universal properties -- Equality, for instance, as
compared with two equal sticks (74a) -- contrasting the changeable
imperfection of the physical world with the exemplary perfection of the
Forms. Medieval philosophers from Augustine on, although largely
lacking in firsthand knowledge of Plato, would argue for illumination
along both of these lines.




Aristotle too seems to invoke the divine. He describes the active
intellect in this way:



> This intellect is separate, unaffected, and unmixed, being
> in essence activity.... It is not the case that it sometimes thinks and
> at other times not. In separation it is just what it is, and this alone
> is immortal and eternal (*De anima* III 5,
> 430a17-23).




There is of course unending controversy over the meaning of this text.
One very common reading, in ancient times and our own, is that this
active intellect is something divine, not a human faculty at all. If
one then makes the further, natural assumption that the active
intellect participates in ordinary human cognition, then Aristotle
would clearly be committed to a version of divine illumination. (One
should, however, be cautious in supposing that Aristotle's *nous
poietikos* plays anything like the role played by the scholastic
*intellectus agens*. See Haldane 1992.) Not everyone has been
persuaded that this active intellect is something literally separate
and divine. But even if one supposes that the active intellect is a
part of the human soul, it is nevertheless difficult to avoid the
suspicion that some sort of special divine influence is at work.
Everything in the passage cries out for some sort of supernatural
element in human cognition. 




Alexander of Aphrodisias (fl. 200 CE) was influential in pushing the
separate-and-divine reading of *De anima* III.5, and Islamic
philosophers (most notably Ibn Sina [980-1037] and Ibn Rushd
[c.1126-c.1198]) would later follow suit. Themistius (4th century CE),
in contrast, championed the part-of-soul reading, and Thomas Aquinas
(1225-1274) would second this interpretation. A full treatment of this
topic would cover the later Aristotelian and Platonic traditions, Greek
and Islamic. But here I will focus exclusively on the Latin West, where
it was Augustine who played the decisive role in formulating the
doctrine of illumination. (For a useful survey of ancient and medieval
Aristotelian accounts of agent intellect, see Brentano 1992. On the
later Platonic tradition, see Gersh 1978. The Islamic tradition
deserves a full essay in its own right, covering not just names well
known in the Latin West, but also figures like Suhrawardi and Mulla
Sadra, central figures in the Islamic illuminationist tradition [see
Walbridge 2005].)


## 3. Augustine




Throughout his long literary career, Augustine (354-430) stresses the
role of divine illumination in human thought. One could choose almost
any work to illustrate this point; here I will focus on the most
familiar of all, the *Confessions*, where Augustine invokes
divine illumination constantly, and makes bold claims for its global
necessity: 



> The mind needs to be enlightened by light from outside
> itself, so that it can participate in truth, because it is not itself
> the nature of truth. You will light my lamp, Lord (IV.xv.25). 
> 
> 
> 
> None other than you is teacher of the truth, wherever and from
> whatever source it is manifest (V.vi.10).
> 
> 
> 
> 
> You hear nothing true from me which you have not first told me
> (X.ii.2).
> 
> 
> 
> 
> Truth, when did you ever fail to walk with me, teaching me what to
> avoid and what to seek.... Without you I could discern none of these
> things (X.xl.65).
> 
> 
> 




Even during the Middle Ages, Augustine's readers disagreed on the
precise nature of his theory. One thing that seems clear from these
passages alone is that divine illumination is an influence that we
receive in an ongoing way throughout our lives. Thomas Aquinas would
later understand illumination as an infusion all at once at the start
(see below), but this seems untenable as an interpretation of
Augustine. The mind needs to be enlightened "from outside itself"; "it
is not itself the nature of truth"; "you *will* light my lamp,
Lord" (he has not done so already); truth "walk[s] with me," rather
than merely setting me in motion at the start.




To speak of this influence as an illumination is of course to use a
metaphor, one not likely to be unpacked fully. Our own minds present
enough of a puzzle to us: when we try to understand how the divine mind
might influence our own, we must inevitably fall back on metaphor.
Still, there are a variety of ways in which we might seek some
clarification. In particular, it is helpful to distinguish two ways in
which God might provide illumination. First, he might simply give us
information of certain kinds, telling us how things are. This is how
illumination is most often understood, at least implicitly. But a
second possibility is that God would provide not the information
itself, but the insight into the truth of the information. On this
second model, we would frame beliefs on our own, and God would
illuminate our minds so that we could see the truth. In other words,
God would supply the justification. It is clear that sometimes
illumination takes the first form: much of Biblical revelation just is
illumination in this sense. But Augustine's theory of illumination
seems largely to be of the second kind. Consider this famous passage
from the *Confessions*:



> If we both see that what you say is true, and we both see
> that what I say is true, then where do we see that? Not I in you, nor
> you in me, but both of us in that unalterable truth that is above our
> minds (XII.xxv.35).




At issue here is biblical interpretation. When a reading is advanced
that seems clearly correct, how is it that everyone listening grasps
the truth of that reading? It is not that God gives us the
interpretation itself, but that he allows us to see that the
interpretation is true. 




This understanding of illumination is particularly apparent in the
*De magistro*, where Augustine argues that only God can teach
us. Of course, other people can tell us things, and can thereby
communicate ideas to us. And we can believe what others tell us:
indeed, our lives would be impoverished if we didn't regularly accept
what others tell us. But all of this stays at the level of mere belief.
It is not knowledge unless we grasp with our minds the truth of what we
are hearing:



> When I speak the truth, I do not teach someone who sees
> these truths. For he is taught not by my words but by the things
> themselves made manifest within when God discloses them
> (12.40).




The speaker's role is not irrelevant in this process. My words give 
listeners an idea that they can then verify for themselves in light of God's
illumination. Illumination is what allows us to go from mere true
belief to knowledge. Illumination provides justification. 




This account is most attractive in cases of a priori knowledge or
pure reasoning, where we grasp through the mind alone that an argument
is valid or that a conclusion is necessary. But there is another strain
of thought running through Augustine, one that focuses on the mind's
ability to transcend the untrustworthy senses and grasp the truth that
lies beyond mere appearances. The following passage is very often cited
in this connection:



> Everything that the bodily senses attain, that which is
> also called sensible, is incessantly changing.... But what is not
> constant cannot be perceived; for that is perceived that is
> comprehended in knowledge. But something that is incessantly changing
> cannot be comprehended. Therefore we should not expect pure truth from
> the bodily senses (*Eighty-three Different Questions*,
> q.9).




In one stroke, this argument rules out the physical world as an object
of pure truth, and rules out the senses as a source for that truth. It
must be the mind, then, with which we attain truth, and that truth must
be something beyond the sensible world. Plainly, the mind cannot rely
on the senses. But what else is there? The conclusion we are invited to
reach is that the mind must rely on God. 




One might try assimilating this line of thought to those passages
where Augustine has in mind necessary a priori truths. But it is more
natural to take this in a different way, as an account of how the mind
goes beyond the sensible data to a grasp of the real essences of
things. Accordingly, the theory of divine illumination would be put to
two very different sorts of work in the later Middle Ages: as an
account of a priori knowledge, and as an account of concept formation.
Each account raises its own set of issues. Taken in the first way,
divine illumination has to compete against the claim that the mind is
naturally capable of grasping such truth. Taken in the second way,
questions immediately arise about the nature of conceptual knowledge.
Do essences (or properties in general) exist in the physical world? Do
they exist only in the divine mind? Do the senses play any role in the
process of concept formation? Later medieval philosophers would handle
these issues in interestingly different ways.


## 4. Thirteenth-century Franciscans




Augustine's position would remain ascendant among Christian
philosophers for most of the Middle Ages. Thirteenth-century
Franciscans, led by figures such as Bonaventure (c.1217-1274) and
Matthew of Aquasparta (c.1237-1302), gave the theory a detailed and
systematic defense, focusing on the changeability and hence uncertainty
of the human mind and the sensory world (see Marrone 2001). Bonaventure
characteristically argues, 



> Things have existence in the mind, in their own nature
> (*proprio genere*), and in the eternal art. So the truth of
> things as they are in the mind or in their own nature -- given that
> both are changeable -- is sufficient for the soul to have certain
> knowledge only if the soul somehow reaches things as they are in the
> eternal art (*De scientia Christi*, q.4 resp.).




Certain knowledge requires steadfast unchangeability. Since that can
be found only in the divine mind, and since we have access to the
divine mind only through illumination, certain knowledge requires
illumination.




This line of argument came to seem increasingly old-fashioned as the
thirteenth century progressed. The growing influence of Aristotle's
theory of cognition, as developed in particular by the Dominican friars
Albert the Great (c.1200-1280) and his student, Thomas Aquinas
(c.1225-1274), offered an impressive picture of how human beings might
be able to achieve certain knowledge despite the changeability of mind
and matter. These developments struck many Franciscans as a betrayal of
Christianity. John Pecham (c.1225-1292), in a letter dating from 1285,
writes



> I do not in any way disapprove of philosophical studies,
> insofar as they serve theological mysteries, but I do disapprove of
> irreverent innovations in language, introduced within the last twenty
> years into the depths of theology against philosophical truth and to
> the detriment of the Fathers, whose positions are disdained and openly
> held in contempt.




Continuing, Pecham criticizes the doctrine 



> which fills the entire world with wordy quarrels, weakening
> and destroying with all its strength what Augustine teaches concerning
> the eternal rules and the unchangeable light.... (quoted in Gilson
> 1955, p.359).




At roughly the same time, Roger Marston (c.1235-1303) writes of those
who, "drunk on the nectar of philosophy ... twisted toward their
own sense all of Augustine's authoritative texts on the unchanging
light and the eternal rules" (*Quaestiones disputatae de anima*
3 ad 30). 




Marston's view is particularly interesting because he proposes a
synthesis of Augustine and Aristotle. On his view,



> It is necessary to posit in our mind, beyond the phantasms
> or abstracted species, something by which we to some degree attain the
> unchanging truths. I believe this to be no different than the influence
> of the eternal light.... For the eternal light, irradiating the human
> mind, makes a certain active impression on it, from which a certain
> passive impression is left in it, which is the formal principle of
> cognizing the unchanging truths (*De anima* 3,
> p.263).




Rather than dismiss the agent intellect as superfluous, Marston
follows Alexander of Aphrodisias et al. in treating the agent intellect
as separate and divine -- indeed, as God himself. Earlier in the
thirteenth century, William of Auvergne (c.1180-1249) had in effect
identified the agent intellect with God (*The Soul* 7.6; cf. Gilson 1926-27, pp.67-72). Such cases illustrate how the
various medieval disputes over whether human beings might share a
single intellect -- so absurd on their face -- are in fact simply
alternative formulations of the dispute over divine illumination. But
there were subtle differences among the various approaches. So whereas
Auvergne largely turns his back on Aristotle, Marston is more
accommodating. In addition to the divine agent intellect, he allows
that each human being possesses its own agent intellect.




On Marston's account, Aristotle and Augustine turn out to be
entirely in harmony: each uses his own terminology to defend the same
theory of divine illumination (*De anima* 3, p. 258).
Etienne Gilson (1933) has characterized Marston's position as
an Avicennized Augustinianism (*Augustinisme avicennisant*).
But this label prejudices the case in favor of Aquinas's perspective:
it assumes that Marston has been seduced by an Islamic misreading of
Aristotle, and it closes off the possibility that Augustine and
Aristotle might have more in common than is typically allowed.




The case of Peter John Olivi (1247/8-1298) demonstrates how
precarious a position the illumination theory held by the 1280s. Olivi,
a Franciscan whose work would eventually be condemned by his own order,
presents a compelling critique of the Augustinian illumination theory
(*I Sent*., q. 2), presenting his comments in the form of
"cautions" (*cavenda*). The theory, he notes, is often very
vague with respect to the actual process of illumination. And in
running through the various possible accounts of the process available
to a defender of the theory, Olivi appears to rule out every one. The
eternal reasons cannot represent things distinctly and specifically,
because then we would have no need of any sensory input. But if the
eternal reasons give us information only of a general and indistinct
sort, then at what level of generality? Does it supply us with
information about species, or genera? If divine illumination is
efficacious at any level, why do we seem to need the senses for all of
our concepts? Olivi's questions and cautions go on and on. But after
laying an entire minefield of this sort for anyone who would defend
divine illumination -- at ad 6 he rejects the Augustinian argument set
out above by Bonaventure -- he nevertheless comes to the surprising
conclusion that he accepts the theory:



> These things, since I don't know how to analyze them fully,
> I set out only as cautions. For although the stated position is in
> itself venerable (*sollemnis*) and sensible, it could
> nevertheless be quite dangerous to those who are not carefully
> supervised. And so I hold the stated position as it is, because it
> belongs to men who are highly venerable. Nevertheless I leave an
> exposition of the above to their wisdom (q. 2, pp. 512-13).




This was a favorite strategy of Olivi's: to criticize a theory
fiercely, exposing seemingly devastating difficulties, and then to
embrace the theory anyway, as a pious gesture of respect. It's hard to
resist reading between the lines, and concluding that dusk was fast
approaching for the theory of divine illumination. 


## 5. Thomas Aquinas




Thomas Aquinas is often thought of as the figure most responsible for
putting an end to the theory of divine illumination. Although there is
some truth to this view, as we will see, it seems more accurate to
regard Aquinas as one of the last defenders of the theory, as a
proponent of innate Aristotelian illumination. 




A vivid example of the way Aquinas moves from an Augustinian to an
Aristotelian framework occurs in his Treatise on Human Nature
(*Summa theologiae* 1a 75-89), where he considers the
Augustinian claim that "pure truth should not be looked for from the
senses of the body" (84.6 obj. 1). In reply, Aquinas invokes the
Aristotelian agent intellect:



> From those words of Augustine we are given to understand
> that truth is not *entirely* to be looked for from the senses.
> For we require the light of agent intellect, through which we
> unchangeably cognize the truth in changeable things, and we distinguish
> the things themselves from the likenesses of things (ad
> 1).




It is not at all clear, here or elsewhere, how the agent intellect
carries out the two tasks he describes. (If Aquinas had given us a
satisfactory account of this, he would have thereby solved two of the leading
problems of epistemology.) But for present purposes it is enough to
notice how Aquinas seems to replace Augustinian illumination with the
Aristotelian agent intellect. Thus the traditional verdict has been
that Aquinas replaced Augustine with Aristotle, and exchanged
illumination for abstraction. 




There is more to the story. In the immediately preceding article,
Aquinas explicitly discusses Augustinian divine illumination, and
reaches the affirmative conclusion that "the intellective soul does
cognize all true things in the eternal reasons" (84.5sc). Often this
affirmative conclusion gets treated as little more than lip service to
the authority of Augustine, and the article as a whole gets taken as a
backhanded repudiation of illumination theory: affirming the theory in
form but denying it in substance. This is a misreading. Aquinas sees
something important in Augustine's theory, something worth
preserving.




Aquinas does reject certain conceptions of divine illumination. He
denies that human beings in this life have the divine ideas as an
*object* of cognition. And he denies that divine illumination is
sufficient on its own, without the senses. Neither of these claims was
controversial. What Aquinas further denies, and what was controversial,
was the claim that there is a special ongoing divine influence,
constantly required for the intellect's operation. Aquinas instead
argues that human beings possess a sufficient capacity for thought on
their own, without the need for any "new illumination added onto their
natural illumination" (*Summa theol*. 1a2ae 109.1c). From one
perspective this makes for an important difference between Aquinas and
his Franciscan contemporaries. But from another perspective the
difference seems slight, because Aquinas is by no means removing God
from the picture. Here is how he expresses his endorsement of
illumination theory:



> It is necessary to say that the human soul cognizes all
> things in the eternal reasons, through participating in which we
> cognize all things. For the intellectual light that is in us is nothing
> other than a certain likeness of the uncreated light, obtained through
> participation, in which the eternal reasons are contained. Thus it is
> said in Psalm 4, *Many say, Who shows us good things?* To this
> question the Psalmist replies, saying *The light of your face, Lord,
> is imprinted upon us*. This is as if to say, through that seal of
> the divine light on us, all things are shown to us (*Summa
> theol*. 1a 84.5c).




There is some temptation to take all of this simply as an expression of
Aquinas's more general view that God is the first cause of all things.
He writes, for instance, 



> *All* active created powers operate in virtue of
> being directed and moved by the Creator. So it is, then, that in all
> cognition of the truth, the human mind needs the divine operation. But
> in the case of things cognized naturally it does not need any new
> light, but only divine movement and direction (*In de trinitate*
> pro. 1.1c).




Here there seems to be nothing special about the intellect's need for
illumination. The intellect, like all of nature, needs God as its first
mover. If you like, think of this as divine illumination. But viewed
under this aspect, it is no wonder the theory was controversial. While
his Franciscan contemporaries were insisting on a special role for God
in human cognition, Aquinas seems to move as far in the opposite
direction as his theism would permit. 




But passages of this last kind are misleading, because Aquinas does
see something especially mysterious about human cognition, and he
appeals to God as a way of solving this mystery. The agent intellect,
on Aquinas's view, accounts for our capacity to grasp self-evident
truths. We have an immediate and direct grasp of the truth of first
principles, such as the principle of noncontradiction (see, e.g.,
*Summa contra Gentiles* II.83.1678). We do not infer the truth
of this principle, we do not discover that it is true through any kind
of induction. Instead we simply see its truth, as soon as we are
confronted with an instance where it applies. This is not innate
knowledge; we are not born knowing these principles. What we are born
with is the capacity to recognize their truth as soon as we are
confronted with instances of them. These first natural conceptions are
"the seeds of all the things that are subsequently cognized" (*De
veritate* 11.1 ad 5). In this sense, Aquinas is even willing to
speak of the soul's having a prior knowledge of everything that it
knows:



> The soul forms in itself likenesses of things inasmuch as,
> through the light of agent intellect, forms abstracted from sensible
> objects are made actually intelligible, so as to be received in the
> possible intellect. *And so, in a way, all knowledge is imparted to
> us at the start*, in the light of agent intellect, mediated by the
> universal concepts that are cognized at once by the light of agent
> intellect. Through these concepts, as through universal principles, we
> make judgments about other things, and in these universal concepts we
> have a prior cognition of those others. In this connection there is
> truth in the view that the things we learn, we already had knowledge of
> (*De veritate* 10.6c).




Because all of what we know can be traced back to these fundamental
principles, there is a sense in which everything we learn, we already
knew. An innate grasp of certain basic truths, recognized by the light
of agent intellect, plays a crucial, foundational role.




The light of agent intellect is of course given to us from God -- "a
certain likeness of the uncreated light, obtained through
participation" (1a 84.5c). Without appealing to God, Aquinas sees no
way of explaining how we recognize the truth of first principles.
Neither deductive nor inductive reasoning can account for the way in
which we immediately *see* that such principles are true. This
insight, then, is simply something we are given:



> The light of this kind of reason, by which principles of
> this kind are known to us, is imparted to us from God. It is like a
> likeness of the uncreated truth reflecting in us. So, since no human
> teaching can be effective except in virtue of that light, it is clear
> that it is God alone who internally and principally teaches us (*De
> veritate* 11.1c).




The light of agent intellect, a likeness of the divine ideas, is the
essential starting point for all knowledge. 




Aquinas agrees with his Franciscan contemporaries that intellective
cognition is incomplete without some sort of supernaturally infused
insight. The only difference is that Aquinas wants that insight to be
given all at once, from the start -- bottled up within agent intellect,
as we might think of it. His opponents, in contrast, think of
illumination as an ongoing process, as necessary as the air we breathe.
It is easy to see how, at the time, this difference might have seemed
important. But from our present perspective the differences seem rather
slight: they seem to be arguing simply over the means of transmission.
Aquinas conceives of illumination as a deep well within us, whereas the
Franciscans conceived of it as raining down in drops. (This is a
summary of the account in Pasnau 2002, Chapter 10.)


## 6. Henry of Ghent




Although in a sense Thomas Aquinas defends a version of divine
illumination, he in another sense clearly weakens the theory by giving
it the status of an innate gift rather than ongoing patronage. In
making for the agent intellect a central place in his theory of
cognition, Aquinas has less room for illumination. As the thirteenth
century progressed, philosophers and theologians were increasingly
willing to make this tradeoff. While the Aristotelian theory of
cognition waxed, the Augustinian theory of divine illumination waned.
To combine the two seemed, in the words of Etienne Gilson
(1930), "unproductive and even, in a sense, contradictory." 




It is this seemingly contradictory task that Henry of Ghent
(c.1217-1293) took upon himself in the years immediately after
Aquinas's death. When Peter John Olivi remarked that he would accept
the theory of illumination because it "belongs to men who are highly
venerable" (sec. 4 above), he would have had in mind among others
Henry of Ghent, who would indeed become known as the "Venerable
Doctor" (*Doctor solemnis*). Ghent was neither Dominican nor
Franciscan, but a so-called "secular" master at the University of
Paris. His project was to defend an Aristotelian theory of cognition
while at the same time reviving divine illumination in its traditional
Augustinian form. To those, like Aquinas, who were arguing for the
self-sufficiency of the human cognitive powers, Ghent replies,



> this is true for natural things, as regards knowing what is
> true of the thing.... Pure truth, however, or any truth that must be
> cognized supernaturally, or perhaps any truth at all, cannot be known
> without God himself doing the teaching (*Summa* 1.7 ad 1).




On Ghent's terminology, to know what is *true* of a thing is
simply to have a veridical impression of it: to represent a thing as it
is. To grasp the *truth* of a thing, in contrast, is to grasp
its nature. Only this latter sort of cognition counts as knowledge in
the strict sense, because only here are we getting at the unchanging
reality of the material world.



> For there is no knowledge of things insofar as they are
> external in effect, but insofar as their nature and quiddity is grasped
> by the mind (*Summa* 2.2 ad 1).




For knowledge of this kind, divine illumination is necessary. 




Ghent's argument is interestingly different from that of Augustine and
his Franciscan followers. Whereas they had dismissed the physical
world as too changeable to be a fit subject for human knowledge, Ghent
believes that pure truth and certain knowledge can be had of the
physical world, provided we manage to grasp the real essences of
things. Since we cannot do so on our own, we need divine illumination
to go beyond sensory appearances, to have genuine insight into the
nature of reality. At its most basic level, Ghent is offering a
critique of the agent intellect. Although he accepts the doctrine of
agent intellect, he refuses to give that faculty the kind of efficacy
that it has for Aquinas and other medieval Aristotelians. Not
surprisingly, Ghent proposes reviving the earlier thirteenth-century
tradition of referring to God himself as a kind of agent intellect
(*Quodlibet* 9.15). The way Ghent would synthesize Augustine
and Aristotle, in this area, is by identifying those aspects of
Aristotle that are incomplete and supplementing them with the
necessary Augustinian illumination. (This is a summary of the account
in Pasnau 1995. All of Henry's important initial article from
his *Summa* on the possibility of knowledge is now available in
a translation from Roland Teske.)


## 7. John Duns Scotus




It was the Franciscan John Duns Scotus, more than anyone else, who put
an end to the theory of divine illumination. As Steven Marrone (2001)
has shown in detail, there were various authors at the end of the
thirteenth century who were ready to reject illumination. Indeed, Ghent
himself gave illumination less and less attention in his later years.
Still, it was Scotus who provided the most impressive and extensive
philosophical alternative to illumination theory. (As John Boler remarked
in correspondence, "as with Nixon's trip to China, it probably
could only be done by a Franciscan.") Scotus criticizes Ghent's
argument in detail (*Ordinatio* I.3.1.4), arguing against
Ghent's own arguments, against the skeptical consequences that would
allegedly come from giving up divine illumination, and against the
viability of such illumination in its own right. With respect to the
last point, Scotus argues that if human cognition were fallible in the
way Ghent argues, then outside illumination could not, even in
principle, ensure "certain and pure knowledge." On Ghent's account, the
human mind cooperates with the divine light in achieving such
knowledge. Scotus replies: 



> When one of those that come together is incompatible with
> certainty, then certainty cannot be achieved. For just as from one
> premise that is necessary and one that is contingent nothing follows
> but a contingent conclusion, so from something certain and something
> uncertain, coming together in some cognition, no cognition that is
> certain follows (*Ordinatio* I.3.1.4 n. 221).




If one part of a system is fallible, then that fallibility infects the
process of a whole. Scotus's startling claim is that if the human mind
were intrinsically incapable of achieving certain knowledge, then not
even divine illumination could save it. 




Scotus's own view is that the human mind is capable of such
knowledge on its own. If by "certain and pure truth" Ghent means
"infallible truth, without doubt and deception," then Scotus thinks he
has established that human beings "can achieve this, by purely natural
means" (*Ord*. I.3.1.4 n. 258). How *can* such a thing be
established? How can the skeptic be refuted, without appealing to
divine illumination? Scotus distinguishes four kinds of knowledge:


* self-evident (*principia per se nota*)
* inductive (*cognita per experientiam*)
* introspective (*cognoscibilia de actibus nostris*)
* sensory (*ea quae subsunt actibus sensus*)




The general strategy is to show that sensory knowledge rests on
inductive knowledge, that inductive knowledge rests on self-evident
knowledge, and that introspective knowledge can be defended as
analogous to self-evident knowledge. Scotus's implicit aim is to shift
as much weight as possible onto the broad shoulders of self-evident
knowledge.




For Scotus, the self-evident is the bedrock on which other sorts of
knowledge rest, and so he does not attempt to locate some further set of
even more basic truths. Instead, he argues that our self-evident
knowledge is foolproof because of certain psychological facts. When one
considers a proposition like *Every whole is greater than its
part*, one immediately grasps that the terms are related in such a
way that the proposition must be true:



> There can be in the intellect no apprehension of the terms
> or composition of those terms without the conformity of that
> composition to the terms emerging (*quin stet conformitas*),
> just as two white things cannot arise without their likeness emerging
> (*Ord*. I.3.1.4 n. 230).




When we see two white objects we immediately grasp, "without doubt
and deception," their similarity to one another. Likewise, when we
grasp a self-evident truth in our mind, we immediately grasp its truth.
Of course, we won't grasp the truth of the proposition if we don't
understand the meaning of the terms, but in that case we won't have
truly formed the proposition in our mind. And in contrast to the
analogous case of recognizing similarity, there is no room for sensory
error here. The senses help us acquire certain concepts, but once we
have those concepts, the senses drop out of the picture -- sensory
reliability becomes irrelevant. Scotus offers the example of a blind
man miraculously shown in his dreams an image of black and white. Once
he acquires these concepts, he can recognize as truly and infallibly as
anyone -- his blindness notwithstanding -- that white is not black
(*Ord*. I.3.1.4 n. 234).




Scotus is unwilling to discard Augustinian illumination entirely,
and so he articulates four senses in which the human intellect sees
infallible truths in the divine light. In each sense, the divine light
acts not on us but on the objects of our understanding. By giving
objects their intelligibility (*esse intelligibile*), the divine
intellect "is that in virtue of which secondarily the objects produced
move the intellect in actuality" (*Ord*. I.3.1.4 n. 267). When
the human mind grasps a self-evident truth, it does so immediately and
infallibly not because the mind has received any special illumination,
but because the terms of the proposition are themselves intelligible:
our grasp of a proposition "seems to follow necessarily from the
character of the terms, which character they derive from the divine
intellect's causing those terms to have intelligible being naturally"
(*Ord*. I.3.1.4 n. 268). It is not that we are illuminated by the
divine light, but that the truth we grasp is illuminated.




This marks a turning point in the history of philosophy, the first
great victory for naturalism as a research strategy in cognitive
theory. On Scotus's account, when we grasp some conceptual truth,
nothing miraculous or divine happens within us: "the terms, once
apprehended and put together, are naturally suited (*sunt nati
naturaliter*) to cause an awareness of the composition's conformity
with its terms" (*Ord*. I.3.1.4 n. 269). It is of course God that
gives the world its intelligibility, just as it is God that creates our
cognitive powers. But what is new in Scotus is the idea that the mind is
not a special case. From this point forward, divine illumination would
rarely be regarded as a serious philosophical possibility.


## 8. Epilogue




It is easy to miss the significance of what Scotus brought about: in
part because it now seems so inevitable, in part because Scotus comes
at the end of a gradual trend toward naturalism, and in part because until only recently
it was generally supposed that nothing of much philosophical importance
happened between Aristotle and Descartes. Yet if one looks at the big
picture of our evolving philosophical/scientific understanding of the
mind, then it is clear that something important happened at the end of
the thirteenth century. 




Still, Scotus's impact should not be overstated. Although divine
illumination, so called, would no longer have many prominent
supporters, the tendency toward supernatural explanations of cognitive
phenomena would survive well beyond the Renaissance. Descartes, to take
one prominent example, can speak of "certain seeds of truth which are
naturally in our souls" (*Discourse on Method* 6, AT VI:64), and of "ideas implanted in the intellect by nature" (*Principles of Philosophy* 2.3). In its details, the view is strikingly similar to Aquinas's: Descartes identifies these ideas as the basis of our knowledge of first principles; he holds that the ideas themselves
are formed only in virtue of sensory impressions; he identifies God as
the ultimate source of these ideas. Moreover, if Descartes is playing
Aquinas, in modern dress, then as Henry of Ghent we can cast
Malebranche, who argues that "All our ideas must be located in the
efficacious substance of the Divinity, which alone is intelligible or
capable of enlightening us, because it alone can affect intelligences"
(*Search after Truth*, p. 232). Malebranche's remarkable view --
in support of which he quotes Augustine -- is that all our ideas are
seen in God. This is illumination theory, all over again. But by the
seventeenth century the philosophical context has changed so
dramatically that these modern developments must be regarded as a
different topic.