Descartes’ Natural Light Reconsidered

Deborah Boyle. Journal of the History of Philosophy. Volume 37, Issue 4. October 1999.


The “natural light” occupies an important position in Descartes’ Third Meditation, where the meditator invokes it to provide the premises needed for his proof for the existence of a non-deceiving God. Descartes also refers to the natural light throughout his Replies to the Objections to the Meditations and in the Principles of Philosophy. Yet he says almost nothing about what the natural light is supposed to be, apparently assuming that his readers already know what he means. English-speaking commentators on Descartes have said little about the natural light, and although French commentators have paid slightly more attention to this topic, they have nonetheless provided no detailed analysis of the concept of the natural light and the role it plays in Descartes’ Meditations.

In 1973, however, John Morris published an article entitled “Descartes’ Natural Light” in the journal of the History of Philosophy, later reprinted in Eternal Truths and the Cartesian Circle. Morris argues that “the understanding can be regarded in an active and a passive sense,” and that the natural light should be equated with the passive function of the intellect. The natural light, he asserts, is

a power of cognition, which contrasts with the “active” power of conceiving. Unlike this power, it does not form ideas, or bring them to consciousness. Instead, it simply gives a click of recognition when a true idea is brought before it.

However, the textual evidence for Morris’ interpretation of the natural light is slender, and in fact the texts support a quite different reading. I shall point out some problems with Morris’ reading, and offer the beginnings of an alternative account.

Activity, Passivity, and the Mind

In the Fourth Meditation, Descartes draws a distinction between two faculties of mind: intellect and will. Intellect, he says, allows him “to perceive the ideas which are subjects for possible judgements” (CSM II 39/AT VII 5), while the will “simply consists in our ability to do or not do something (that is, to affirm or deny, to pursue or avoid)” (CSM II 40/AT VII 57). Although he does not say so in the Fourth Meditation, Descartes suggests in two 1641 letters to Regius that the intellect is passive and the will is active; strictly speaking, he says, “understanding [intellectio] is the passivity of the mind and willing [volitio] is its activity” (CSMK III 182/AT III 372). A few months later, he writes that “we should use the term ‘action’ for what plays the role of a moving force, like volition in the mind, while we apply the term ‘passion’ to what plays the role of something moved, like intellection [intellectio] and vision in the same mind” (CSMK III199/AT III 454-5). And in the Passions of the Soul Descartes states that while volitions are actions, “the various perceptions or modes of knowledge present in us may be called its passions, in a general sense” (CSM I 335/ AT XI 342).

In his early work, the Rules for the Direction of the Mind, Descartes does refer to “actions of the intellect.” If we do not allow for changes in Descartes’ thinking, we might assume that at the time of the Meditations, too, he would be willing to speak of “actions of the intellect.” But Descartes provides no account of the will in the Rules; thus any activity he might have attributed to the mind would have to be included in the role of the intellect. In the Meditations, Descartes’ philosophy of mind has expanded to provide a place for the will, which can take over the active functions previously assigned to the intellect.

John Morris’ reading of the role of the natural light in the Meditations takes as its starting point a passage in the Rules where Descartes claims that the intellect itself, the cognitive power or vis cognoscens, has both active and passive functions; it is, he says, sometimes like a seal, sometimes like wax. After describing the various functions of the cognitive power, Descartes concludes that “according to its different functions, then, the same power is called either pure intellect, or imagination, or memory, or sense-perception. But when it forms new ideas in the corporeal imagination, or concentrates on those already formed, the proper term for it is `native intelligence’ [ingenium]” (CSM I 42/AT X 416). Morris takes the latter distinction, between forming new ideas and concentrating on already formed ideas, to be spelling out the difference between the active and passive functions of the vis cognoscens, and he offers special vocabulary to label these functions: he calls the ability of the intellect to create new ideas the “power of conceiving,” and the intellectual function which “concentrates on those already formed” the “power of cognition,” .power of knowing,” or “power of recognition.” The former is active, while the latter is passive.

There are several problems with this reading. First, it is not clear that Descartes means to equate the active and passive functions of the vis cognoscens with the two functions he calls ingenium; the functions of ingenium seem rather to be two uses among several to which the cognitive power can be put. Furthermore, ingenium is explicitly said to be concerned with ideas in the corporeal imagination [phantasia], and Descartes appears to contrast it with the cognitive ability “when it acts on its own”-that is, with pure intellect (CSM I 42/AT X 416). The natural light, we shall see, involves the operation of pure intellect, and does not require turning to the imagination in any way; hence it cannot be equivalent to either the passive or the active aspect of the “native intelligence” Descartes mentions here.

Moreover, there is no evidence that Descartes continued, after the time of the Rules, to maintain that the intellect itself had active and passive roles. In an earlier article, “Raison, Connaissance and Conception in Descartes’ Meditations,” Morris concedes that the December 1641 letter to Regius indicates that from the will. Descartes indeed refers to a puissance de connaitre, which he equates with the entendement, or understanding, and to a puissance dWire, or volonte, will (AT IX 45). Thus the puissance de connaitre seems to be equivalent to the understanding in general. On the next page, Descartes refers to “la puissance d’entendre ou de concevoir” (AT IX 46); again, the puissance de concevoir is equated with the understanding. In other words, connaitre and concevoir both seem to pertain to the understanding in general, not to distinct parts of the understanding.

Moreover, Descartes characterizes the entendement, which he has just equated with the puissance de connaitre, as that by which he perceives ideas; in the Latin original he uses the verb percipio (AT VII 56), and in the French translation it is concois (AT IX 45). But, as we have seen, Morris wants to match instances of the verbs concevoir and percipere with the supposedly active puissance de concevoir, and not with the supposedly passive puissance de connaitre. Clearly, the passage at AT IX 45 flies in the face of Morris’ interpretation.

Later on that page, Descartes refers to “la faculte de concevoir.” If Morris is right, then Descartes presumably means to contrast this faculty with the faculte de connaitre mentioned a few lines earlier, and to contrast both of those (as parts of the intellect) with the will. But in fact it seems that Descartes’ reference to the faculte de concevoir is meant to spell out in greater detail what is involved in the puissance de connaitre, for Descartes is saying that if he considers either “la faculte de concevoir” or “la memoire, ou l’imagination, ou quelqu’autre puissance,” he finds that all are limited, while only his will appears unlimited. He thus seems to be grouping the various faculties of intellect and opposing them to the will; since, earlier in the paragraph, he also opposed intellect to will, it seems plausible to read the faculties of conceiving, memory, and imagination as types of knowing. If this is right, then by puissance de connaitre Descartes is referring in the most general way to the understanding or intellect, and not to a particular function of the intellect.

The passage at AT IX 45 seems to be Morris’ main evidence for his claim that the passive role of the understanding is the puissance de connaitre, but he also mentions in a footnote to his article that the reader should see the passages at AT IX 57 and 63. The first of these passages is in the opening paragraph of the Sixth Meditation, where the meditator remarks that “when I give more attentive consideration to what imagination is, it seems to be nothing else but an application of the cognitive faculty to a body which is intimately present to it, and which therefore exists” (CSM II 50/AT VII 7’2). In French the reference is to “la faculte qui connait,” and in Latin it is to “facultatis cognoscitivae.” But this passage in no way suggests that this faculty is passive. The passage at AT IX 63, also in the Sixth Meditation, does use the word connaitre (cognoscendi in the Latin) in connection with a faculty which the meditator explicitly identifies as passive: “Now there is in me a passive faculty of sensory perception, that is, a faculty for receiving and recognizing the ideas of sensible objects” (CSM II 55/AT VII 79). This passage might supply slightly more reason to think that words like connaitre and cognosco always have a passive connotation in the Meditations, except that in this passage Descartes mentions receiving as well as recognizing; so it seems possible that it is the “receiving” which is being characterized as passive, and not the “recognizing.”

Thus it seems that there is really no textual evidence for Morris’ claims that Descartes distinguished two functions of understanding, that these “are called” the power of recognizing and the power of conceiving, and that they are, respectively, passive and active.

A further problem with Morris’ reading is that it seems very odd to say that cases of percipere are active, for this has the result that when Descartes says things like “Now all that the intellect does is to enable me to perceive [percipio] the ideas which are subjects for possible judgments” (CSM II 39/AT VII 56), or “the perception [perceptionis] of the intellect should always precede the determination of the will” (CSM II 41/AT VII 60), he is portraying the intellect as acting. For support, Morris points out that in the wax passage, Descartes refers to “the perception I have of it, or rather the act whereby it is perceived” (CSM II 21/AT VII 31)-but Morris should have noted that this gloss on “perception” appears only in the French translation (AT IX 24). We have already seen that Descartes’ Fourth Meditation distinction between intellect and will is plausibly read as a distinction between a passive and an active power of mind, that Descartes says in The Passions of the Soul that perceptions of the mind are passive, and that there is no evidence to suggest that Descartes’ claim in the Rules that the “knowing power” has active and passive functions can be read into the Meditations.

There is only one sense in which it is correct to say that for Descartes the intellect has both active and passive functions. In the Fourth Meditation, the meditator distinguishes the intellect [intellectus] from the will [voluntas], and I have argued that although he does not say so there, Descartes takes the intellect to be passive and the will to be active. But before the Fourth Meditation, the meditator has used intellectus as a synonym for mind; in the Second Meditation, for example, he declares that “I am in the strict sense only a thing that thinks; that is, I am a mind, or intelligence, or intellect, or reason [id est, mens, sive animus, sive intellectus, sive ratio]” (CSM II 18/AT VII 27). In this case, “intellect” refers to the complex that turns out, in the Fourth Meditation, to include the two faculties of will and intellect in the strict sense. In other words, there is a narrow and a broad sense of intellectus. Intellectus in the broad sense includes whatever pertains to the mind, ruling out only that which pertains to the body and its senses; while intellectus in the narrow sense excludes both the will and the bodily senses.

Now, insofar as the will can be included in the broader sense of intellect, it could be appropriate to say that some intellectual processes are active. Indeed, many uses of the mind, for Descartes, do involve the activity of the will; the will passes judgment on the perceptions in the intellect, and the will is presumably also involved when one exercises one’s imagination by joining two or more ideas together, or when one makes inferences, or engages in the process of analysis. And consider Descartes’ remark in The Passions of the Soul:

When our soul applies itself to imagine something non-existent-as in thinking about an enchanted palace or a chimera-and also when it applies itself to consider something that is purely intelligible and not imaginable-for example, in considering its own nature-the perceptions it has of these things depend chiefly on the volition which makes it aware of them. That is why we usually regard these perceptions as actions rather than passions. (CSM I 336/AT XI 344)

Descartes might be suggesting here that although we regard these perceptions as actions rather than passions, we are mistaken to do so. But the important point for our purposes is that he does not deny that perceptions of purely intelligible things or of non-existent things do indeed require a volition. The role of this volition is evidently to direct the intellect’s attention; later in the Passions, Descartes describes how volitions can, through their “power to make the [pineal] gland move,” lead us to have various perceptions in the intellect (CSM I 344/AT XI 361). These, then, are examples of intellectual processes which can be called active insofar as the will is involved.

The Natural Light and the Role of the Will

After distinguishing between the active and passive functions of intellect, Morris argues that we should identify the natural light with the passive function of recognition. To do this, he must show that the natural light is itself a passive faculty. He states:

According to this analysis, the natural light is a ‘passive’ function, a power of cognition, which contrasts with the ‘active’ power of conceiving. Unlike this power, it does not form ideas, or bring them to consciousness. Instead, it simply gives a click of recognition when a true idea is brought before it; Descartes invariably uses it in expressions like ‘I recognize (connais) by the natural light.’ He could never say, ‘I conceive by the natural light’; conceiving simply isn’t the sort of function that the natural light’ performs. Morris provides no further argument. Thus his evidence for the claim that the natural light is passive apparently consists entirely in the putative fact that Descartes typically says “I recognize [connais] by the natural light,” where we must understand connais in the passive sense which Morris attributes to it.

I have already argued that connaitre does not have the technical meaning, contrasting with the sense of concevoir, that Morris attributes to it. Furthermore, neither the French nor the Latin versions of the Meditations support Morris’ claim about how Descartes uses the phrase “natural light.” The French translation does use personal pronouns more than the Latin version, especially the first person plural pronoun, which does not appear at all in the original Latin. However, only one of the seven cases of truths said to be manifest by the natural light in the Meditations actually takes the form “I recognize by the natural light,” and this is true only of the French translation. The passage occurs in the Sixth Meditation, when the meditator refers to “une infinite d’autres semblables, que je connais par la lumiere naturelle sans l’aide du corps” (AT IX 65). The original Latin reads “reliqua omnia quae lumine naturali sunt nota” (AT VII 82), and all the other accounts of truths revealed by the natural light in the Latin text are of the form “X is manifest/perspicuous/known/shown by the natural light.” These constructions are indeed passive, but that need not imply that the natural light is itself passive. “The natural light” in all these examples is in the ablative case, which in Latin is often used to express the means by which an action is accomplished. But Descartes’ definition of action as “whatever takes place or occurs . . . with regard to that which makes it happen” (CSM I 328/AT XI 328) can be applied even to things which lack their own motive force, such as tools. So this is inconclusive evidence for settling the question of whether the natural light is active or passive.

In the Sixth Meditation, the meditator says that all the things known by the natural light “belong to the mind alone” rather than to the body or to the combination of body and mind (CSM II 57/AT VII 82). But the mind, we have seen, is made up of intellect and will; with which of these ought the natural light to be associated? In the Fourth Meditation, “natural light” is presented as a synonym for “power of understanding” [vim intelligendi], suggesting that it should be associated with the intellect, which is passive, and not with the will, which is active. However, to say that the natural light is an operation of the intellect rather than the will is not to say that the will plays no role when the natural light operates. Referring to his earlier assertion that his freest judgments are those in which he feels compelled by his own will to assert or deny, the meditator writes in the Fourth Meditation:

For example, during these past few days I have been asking whether anything in the world exists, and I have realized that from the very fact of my raising this question it follows quite evidently that I exist. I could not but judge that something which I understood so clearly was true; but this was not because I was compelled so to judge by any external force, but because a great light in the intellect was followed by a great inclination in the will. (CSM II 41/AT VII 58-9)

The proposition that the meditator is here referring to is one that he has already explicitly said (at CSM II 27/AT VII 38) was shown by the natural light. In other words, this Fourth Meditation passage is describing what happens when something is perceived by the natural light: there is such a great inclination in the will that one feels compelled to assent.

Descartes emphasizes that, in God, intellect and will are not distinct faculties. In the operation of the natural light, human beings more closely resemble God, for when the natural light shines in the intellect, the activity of the will inevitably follows, and perhaps follows so closely that the two appear to be simultaneous. This inseparability of the operation of the passive natural light from the operation of the active will might even entitle us to call the natural light, more broadly speaking, active. We saw earlier that Descartes allows in the Passions that we tend to regard some perceptions as actions insofar as our having the perception depends on a prior volition which serves to direct the intellect’s attention (CSM I 336/AT X 344); it could also be legitimate to regard a perception as an action if the perception is inevitably followed by a volition. Thus, although by “natural light” strictly speaking Descartes means only the perception of certain ideas in the intellect, which is a passive operation, there is a sense in which the natural light is active, insofar as the active will inevitably asserts the truth of whatever proposition has been illuminated by the natural light.

The truths illuminated by the natural light, then, are propositions to which the will feels compelled to assent: some proposition is perceived so clearly and distinctly that it is as if a great light has illuminated the proposition in the mind, and the will immediately grants that the proposition is true. The “light” occurs only in the intellect, as the idea is perceived, but the action of the will cannot be separated from the light; it is impossible, Descartes would say, for someone to perceive the idea and not assent. This seems to be Descartes’ meaning when he asserts, in the Second Set of Replies, that “as soon as we think that we correctly perceive something, we are spontaneously convinced that it is true” (CSM II 103/AT VII 144), and when he makes a similar claim in the Third Meditation:

Yet when I turn to the things themselves which I think I perceive very clearly, I am so convinced by them that I spontaneously declare: let whoever can do so deceive me, he will never bring it about that I am nothing, as long as I continue to think that I am something; or to make it true at some future time that I have never existed, since it is now true that I exist; or bring it about that two and three added together are more or less than five, or anything of this kind in which I see a manifest contradiction. (CSM II 25/AT VII 36)

This reading contrasts with John Morris’ interpretation of the natural light in an important way, for Morris ignores the role of the will in his account. Indeed, if his account were right, it would render the will superfluous in Descartes’ system. Morris maintains that the passive power of knowing or recognizing, the natural light, allows us to “recognize truth or falsehood,” and that the natural light “simply gives a click of recognition when a true idea is brought before it.” But consider the following passage from the Fourth Meditation:

In order to be free, there is no need for me to be inclined both ways; on the contrary, the more I incline in one direction-either because I clearly understand that reasons of truth and goodness point that way, or because of a divinely produced disposition of my inmost thoughts-the freer is my choice. (CSM II 40/AT VII 57-8)

On a reading like Morris’, Descartes would be read as suggesting that the will is wholly inclined to assent to a claim when-and because-the understanding already recognizes that the claim is true. And if that is so, then it seems a judgment has somehow already been made, before the will enters the picture. But Descartes emphasizes at the end of the Fourth Meditation that it is on the basis of the clarity and distinctness of a proposition that one judges that proposition to be true; the former are criteria of the latter. When we perceive certain objective truths, our perception has “transparent clarity” (CSM II 135/AT VII 192; see also CSM II 104/AT VII 145-6); but the recognition that it is true only occurs when the will assents. On the reading which Morris seems forced to give, Descartes’ distinction between clarity and distinctness on the one hand and truth on the other hand collapses. Perhaps one might try to cash out Morris’ characterization of the natural light as the faculty which gives a “click of recognition” when an idea is true in terms of the will, for what could such a “click” be, if not assent to the truth of a proposition? But such an elaboration of Morris’ view would be incoherent, since he thinks both that the natural light is passive and that the natural light is what gives the “click”; for only the active Cartesian will can give anything like a “click.”

Indeed, the natural light should not be taken as a power of recognition at all, for any such interpretation opens the door to an infinite regress: to recognize that some perception is clear and distinct is presumably to judge that it is clear and distinct, and so a judgment seems to be necessary even before the perception is judged to be true. But, as I have pointed out, Descartes does not characterize the natural light as “recognizing” anything; that is simply Morris’ vocabulary. Rather, we should read Descartes as saying that particularly clear and distinct perception makes the intellect seem to be illuminated by a great light, and the assent of the will invariably follows.

In sum, the natural light is not, as Morris claims, a “power of cognition, which contrasts with the ‘active’ power of conceiving” and which gives a “click of recognition when a true idea is brought before it.” I have argued that although Morris is right to associate the natural light with the passive function of intellect, he is wrong to claim that the intellect has an additional active function; Descartes did attribute active and passive roles to the intellect in his early Rules, but only because he had not yet developed his later distinction between intellect and will. This error already undermines Morris’ attempt to identify a distinction between a passive “power of cognition” and an active “power of conceiving” in the Meditations, but that project is further doomed by the fact that the Cartesian texts simply do not support Morris’ contention that Descartes uses connaftre and concevoir to refer to distinct parts of the understanding, or that these words connote, respectively, a passive and an active power. Moreover, by suggesting that the natural light “clicks” when it recognizes a true proposition, Morris attributes to the natural light a function which Descartes himself attributes to the will.

I have argued that the natural light is indeed passive, but that this is because Descartes associates it with the “power of understanding” [vim intelligendi], where that is contrasted with the will. However, the natural light is very closely tied to the operation of the will; when the intellect perceives some proposition particularly clearly and distinctly, the will feels itself compelled to assert the truth of that proposition, and in these cases Descartes says that the natural light has shone.