After becoming more familiar with his true nature as res cogitans, and the various modes of thinking included in that characterisation, Descartes now looks to other ideas to test their certainty. He discovers a way of escaping from the sceptical doubt by only trusting clear and distinct perceptions, and a warrant for that criterion in the existence of God.
At this point, Descartes has only a very slight foundation for future knowledge: the single, indubitable truth ‘I exist’ and some awareness of his nature as a thinking thing. To progress beyond this he must adjust his method. Since he is unlikely to stumble upon other truths as self-evident as the cogito (which is a unique type of intuition), he wonders instead what it is about his knowledge so far that gives it such certainty, and whether this feature may belong to other propositions too.
I am certain that I am a thinking thing. Do I not therefore also know what is required for my being certain about anything? M3 p24
The (slightly disappointing) answer is that he sees the truth with clarity and distinctness – or, as he puts it elsewhere in the Meditations, by the ‘natural light’ of reason (eg p27). This allows him to formulate a general rule for proceeding with his investigation: ‘whatever I perceive very clearly and distinctly is true’ (p24). We have to look to another work to find a definition of these terms:
I call a perception ‘clear’ when it is present and accessible to the attentive mind—just as we say that we see something clearly when it is present to the eye’s gaze and stimulates it with a sufficient degree of strength and accessibility. I call a perception ‘distinct’ if, as well as being clear, it is so sharply separated from all other perceptions that it contains within itself only what is clear. Principles I.45
The model for such clear and distinct ideas is, as usual, geometry. Descartes ‘sees’ with great clarity that a triangle has three sides: this is a truth of reason, impossible to doubt; an immediate intuition known a priori and not via the senses (the senses offer perceptions which are usually clear or vivid, but certainly not distinct, as the discussion of the piece of wax revealed). Like the cogito, such a priori truths are self-evident – and being self-evident, they feel a certain way. This is the certainty of a clear and distinct perception. Of course, such truths also have minimal content, as you would expect from analytic statements like ‘every triangle has three sides’. This minimal content seems to be a condition of distinct perception. It is interesting to ask whether such minimal concepts are substantial enough to be useful; and whether more substantial concepts can be perceived with the necessary distinctness.
There is also a degree of subjectivity involved in this process, which is perhaps unexpected in a search for objective truth. Descartes’ criterion here is internal: the truth of a proposition becomes apparent from an examination of the idea (if it is perceived clearly and distinctly). A more common view is that a criterion of truth must, in fact, be external: a proposition is true because of some relation it has to the world (resemblance, for example, or correspondence). The internal criterion allows for the possibility that what is clear and distinct to Descartes may not be clear and distinct to another observer; hence, the question of truth becomes oddly subjective. There is obviously a crucial difference between someone feeling certain and a proposition being certain: it is no contradiction to say that I feel certain about something, but I am wrong. Descartes needs to eliminate this gap: the two things must necessarily coincide if he is to proceed with his psychological criterion. And for that to be the case, he needs a guarantee that internal certainty always corresponds to external truth: that the certainty he feels proceeds from the truth of things. That guarantee, of course, is God’s benevolence.
Descartes will seek to prove the existence of God precisely to provide this epistemic warrant: but at this point he faces something of a problem. The types of belief that he perceives clearly and distinctly are a priori truths of reason and mathematics:
... 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, so long as I continue to think I am something; or 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. M3 p25
But, of course, Descartes has been here before in the First Meditation. Even such self-evident truths may be illusions generated by a deceiving God, and therefore cannot be considered beyond doubt. Descartes admits as much here, although he makes light of it: such doubt is ‘a very slight and, so to speak, metaphysical one’ (p25). But the fact that he can doubt such knowledge suggests that he does not perceive it with the clarity and distinctness he claims; or if he does, that such clarity and distinctness cannot be immune to doubt.
Sometimes Descartes seems to suggest that nothing is immune to the Deceiving God Argument; and sometimes he suggests that certain beliefs are immune if, like the cogito, they are perceived with sufficient clarity and distinctness. His argument in this Meditation is best served by taking the second line. The truths of arithmetic, for example, seem to be immune to doubt. That is not to say that mistakes are not made: it is of course possible that an elementary error of arithmetic may mean that any sum, even 2 + 3 = 5, is wrongly calculated. But if someone does believe that 2 + 3 = 4, say, surely that is only because they are not seeing the numbers clearly and distinctly: an unclouded and attentive mind will see that 2 + 3 = 5 and recognise its truth with total certainty. In the case of the cogito, Descartes’ certainty persisted ‘for as long as I am thinking’: and clear-sighted mathematicians will have similar certainty for as long as they clearly and distinctly perceive that 2 + 3 = 5. Perhaps tomorrow the mathematicians will have lost that certainty, but as soon as they attend to the problem again, it will return. Without these special cases of certainty, Descartes has nowhere to go. In order to prove that God is not a deceiver, he will need some truths that are immune to the Deceiving God Argument. We have here the first intimations of the Cartesian Circle.
Still, this is not entirely satisfactory as Descartes is now assuming as indubitably true propositions which were earlier open to doubt. It appears that the sweeping scepticism of the First Meditation was not, in fact, as coherent and persuasive as it seemed. But that need not be a problem, since Descartes was only using such techniques to discover the limits of scepticism. And those limits appear to have been reached in the case of clear and distinct perceptions.
Descartes has already identified four faculties of the mind: intellect (or understanding), will, imagination and sensation. Corresponding roughly to these four faculties are different classes of thought. By introspecting, Descartes discovers three kinds: ideas proper (that is, concepts); volitions (or emotions); and judgements. Judgements are, technically, the only thoughts that can be true or false:
And the chief and most common mistake which is to be found here consists in my judging that the ideas which are in me resemble, or conform to, things located outside me. M3 p26
This is the first suggestion of Descartes’ theory of error, a looming problem for a philosopher about to prove that God never deceives. The account of human error will focus on such judgements; that is, wrongly believing that ideas resemble real things. As an example, Descartes describes two different ideas of the sun: one derived from his senses which makes the sun appear small; and one derived from astronomical reasoning which shows the sun to be much larger than the earth (p27). Clearly both ideas cannot be accurate, and we know that the visual impression of the sun bears no resemblance to its real size. To judge that it does on the testimony of his senses, is to fall into error.
Judgements and volitions (desires, fears and so on) are joint operations of the intellect and will. But Descartes is most interested here in the third kind of thought which he properly terms ‘ideas’:
... as it were the images of things... for example, when I think of a man, or a chimera, or the sky, or an angel, or God. M3 p25
The qualification ‘as it were’ is important there: Descartes does not intend a pictorial representation of God, for example. Some ideas do present themselves as images, no doubt: but Descartes means something closer to our term ‘concept’.
Now as far as ideas are concerned, provided they are considered solely in themselves and I do not refer them to anything else, they cannot strictly speaking be false; for whether it is a goat or a chimera that I am imagining, it is just as true that I imagine the former as the latter. M3 p26
Later on in this Meditation, Descartes will suggest that such ideas can be considered ‘materially false’ (p30) if they ‘represent non-things as things’. Ideas that lack clarity and distinctness can lead the thinker to believe in external objects that are not as they appear (like the sun), and such ideas could loosely be termed false. But for now, Descartes is more interested in the source of these ideas.
By a process of elimination, ideas will be the objects of the senses or the imagination (the two faculties not yet discussed). Ideas coming from outside through the senses are described as ‘adventitious’; those generated by the imagination are ‘invented’. But Descartes also offers a third category: ‘innate’ ideas (which will turn out to be discoverable by the intellect alone). Although the term derives from ‘in-born’, it is not necessary for Descartes that such innate ideas are present at birth. Rather, they are somehow hardwired into the human mind, already part of the operating system (as it were). By contrast, think of an adventitious idea (like the tree outside the window) or an invented one (a chimera). Innate ideas are crucial for Descartes (and his rationalist successors) but they were flatly rejected by empiricists like John Locke who insisted that all ideas must be adventitious or invented.
At this point, however, Descartes is more curious about those ideas which he takes to originate from outside himself. Since they are not subject to his will (he cannot choose what to see or taste or hear) he is inclined to believe that they resemble the external objects that cause them. But of course he might be dreaming; or, as the example of the sun demonstrates, there may be no significant resemblance between an idea and its object. That is the problem that the existence of God is designed to solve.
By reflecting on these ideas, particularly their ‘objective reality’, Descartes arrives at the first proof(s) of the existence of a good God who guarantees that clear and distinct perceptions truthfully represent their objects. The Trademark Argument and the Contingency Argument allow Descartes to construct a bridge from the internal certainty of the cogito to the external reality of the material world.