Descartes on Second Replies

Suppose someone does not discern any cause cooper ating in the production of a fly which possesses all the degrees of perfection possessed by the fly; suppose further that he is not sure whether there is any additional cause beyond those which he does discern: it would be quite irrational for him to take this as a basis for doubting something which, as I shall shortly explain at length, is manifest by the very light of nature.  [135]

Those who give the matter their careful attention and spend time meditating with me will clearly see that there is within us an idea of a supremely powerful and perfect being, and also that the objective reality of this idea cannot be found in us, either formally or eminently. I cannot force this truth on my readers if they are lazy, since it depends solely on their exercising their own powers of thought. [136]

But what about when I was considering something very simple and straightforward in arithmetic or geometry, for example that two and 36 three added together make five, and so on? Did I not see at least these things clearly enough to affirm their truth? Indeed, the only reason for my later judgement that they were open to doubt was that it occurred to me that perhaps some God could have given me a nature such that I was deceived even in matters which seemed most evident. And whenever my preconceived belief in the supreme power of God comes to mind, I cannot but admit that it would be easy for him, if he so desired, to bring it about that I go wrong even in those matters which I think I see utterly clearly with my mind's eye. Yet when I turn to the things them selves 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. And since I have no cause to think that there is a deceiving God, and I do not yet even know for sure whether there is a God at all, any reason for doubt which depends simply on this supposition is a very slight and, so to speak, metaphysical one. But in order to remove even this slight reason for doubt, as soon as the opportunity arises I must examine whether there is a God, and, if there is, whether he can be a deceiver. For if I do not know this, it seems that I can never be quite certain about anything else. [25]

Admittedly my nature is such that so long as' I perceive something very clearly and distinctly I cannot but believe it to be true. But my nature is also such that I cannot fix my mental vision continually on the same thing, so as to keep perceiving it clearly; and often the memory of a previously made judgement may come back, when I am no longer attending to the arguments which led me to make it. And so other arguments can now occur to me which might easily undermine my opinion, if I were unaware of God: and I should thus never have true and certain knowledge about anything, but only shifting and changeable opinions. For example, when I consider the nature of a triangle, it appears most evident to me, steeped as I am in the principles of geometry, that its three angles are equal to two right angles; and so long as I attend 7o to the proof, I cannot but believe this to be true. But as soon as I turn my mind's eye away from the proof, then in spite of still remembering that I perceived it very clearly, I can easily fall into doubt about its truth, if I am unaware of God. For I can convince myself that I have a natural disposition to go wrong from time to time in matters which I think I perceive as evidently as can be. This will seem even more likely when I remember that there have been frequent cases where I have regarded things as true and certain, but have later been led by other arguments to judge them to be false. [48]

Thirdly, you are not yet certain of the existence of God, and you say that you are not certain of anything, and cannot know anything clearly and distinctly until you have achieved clear and certain knowledge of the existence of God.' It follows from this that you do not yet clearly and distinctly know that you are a thinking thing, since, on your own admission, that knowledge depends on the clear knowledge of an existing God; and this you have not yet proved in the passage where you draw the conclusion that you clearly know what you are.

Moreover, an atheist is clearly and distinctly aware that the three angles of a triangle are equal to two right angles; but so far is he from supposing the existence of God that he completely denies it. According to the atheist, if God existed there would be a supreme being and a supreme good; that is to say, the infinite would exist. But the infinite in every category of perfection excludes everything else whatsoever — every kind of being and goodness, as well as every kind of non-being and evil. Yet in fact there are many kinds of being and goodness, and many kinds of non-being and evil. We think you should deal with this objection, so that the impious have no arguments left to put forward. [89]

Thirdly, when I said that we can know nothing for certain until we are aware that God exists,2 I expressly declared that I was speaking only of knowledge of those conclusions which can be recalled when we are no longer attending to the arguments by means of which we deduced them.' Now awareness of first principles is not normally called 'knowledge' by dialectitians. And when we become aware that we are thinking things, this is a primary notion which is not derived by means of any syllogism. When someone says 'I am thinking, therefore I am, or I exist', he does not deduce existence from thought by means of a syllogism, but recognizes it as something self-evident by a simple intuition of the mind. This is clear from the fact that if he were deducing it by means of a syllogism, he would have to have had previous knowledge of the major premiss `Everything which thinks is, or exists'; yet in fact he learns it from experiencing in his own case that it is impossible that he should think 141 without existing. It is in the nature of our mind to construct general propositions on the basis of our knowledge of particular ones.

The fact that an atheist can be 'clearly aware that the three angles of a triangle are equal to two right angles'' is something I do not dispute. But I maintain that this awareness of his is not true knowledge, since no act of awareness that can be rendered doubtful seems fit to be called know ledge.' Now since we are supposing that this individual is an atheist, he cannot be certain that he is not being deceived on matters which seem to him to be very evident (as I fully explained). And although this doubt may not occur to him, it can still crop up if someone else raises the point or if he looks into the matter himself. So he will never be free of this doubt until he acknowledges that God exists.

It does not matter that the atheist may think he has demonstrations to prove that there is no God. For, since these proofs are quite unsound, it will always be possible to point out their flaws to him, and when this happens he will have to abandon his view. [100-101]

"'Nothing," you reply, "absolutely nothing".' I have explained, in D several places, the sense in which this 'nothing' is to be understood. It is this. So long as we attend to a truth which we perceive very clearly, we cannot doubt it. But when, as often happens, we are not attending to any truth in this way, then even though we remember that we have previously perceived many things very clearly, nevertheless there will be nothing which we may not justly doubt so long as we do not know that whatever we clearly perceive is true. 1 But my careful critic here takes 'nothing' quite differently. From the fact that at one point I said that there was nothing that we might not doubt — namely in the First Meditation, in which I was supposing that I was not attending to anything that I clearly perceived — he draws the conclusion that I am unable to know anything certain, even in the following Meditations. This is to suggest that the reasons which may from time to time give us cause to doubt something are not legitimate or sound unless they prove that the same thing must be permanently in doubt.

[Descartes] 'I was not guilty of circularity when I said that the only reason we have for being sure that what we clearly and distinctly perceive is true is the fact that God exists, but that we are sure that God exists only because we perceive this clearly.' CSMK  334

[Burman] It seems there is a circle. For in the Third Meditation the author uses axioms to prove the existence of God, even though he is not yet certain of not being deceived about these.

[Descartes] He does use such axioms in the proof, but he knows that he is not deceived with regard to them, since he is actually paying attention to them. And for as long as he does pay attention to them, he is certain that he is not being deceived, and he is compelled to give his assent to them.

[Burman] But our mind can think of only one thing at a time, whereas the proof in question is a fairly long one involving several axioms. Then again, every thought occurs instantaneously, and there are many thoughts which come to mind in the proof. So one will not be able to keep the attention on all the axioms, since any one thought will get in the way of another. [334-335]

[Descartes] Firstly, it is just not true that the mind can think of only one thing at a time. It is true that it cannot think of a large number of things at the same time, but it can still think of more than one thing. For example, I am now aware and have the thought that I am talking and that I am eating; and both these thoughts occur at the same time. Then, secondly, it is false that thought occurs instantaneously; for all my acts take up time, and I can be said to be continuing and carrying on with the same thought during a period of time.

[Burman] But on that showing, our thought will be extended and divisible.

[Descartes] Not at all. Thought will indeed be extended and divisible with respect to its duration, since its duration can be divided into parts. But it is not extended and divisible with respect to its nature, since its nature remains unextended. It is just the same with God: we can divide his duration into an infinite number of parts, even though God himself is not therefore divisible ... Accordingly, since our thought is able to grasp more (149) than one item in this way, and since it does not occur instantaneously, it is clear that we are able to grasp the proof of God's existence in its entirety. As long as we are engaged in this process, we are certain that we are not being deceived, and every difficulty is thus removed.

'The fact that there can be nothing in the mind, in so far as it is a thinking thing, of which it is not aware, seems to me to be self-evident.

[Burman] But how can it be aware, since to be aware is itself to think? In order to have the thought that you are aware, you must move on to another thought; but if you do this, you can no longer be thinking of the thing you were thinking of a moment ago. It follows that you cannot be aware that you are thinking, but only that you were thinking.

[Descartes] It is correct that to be aware is both to think and to reflect on one's thought. But it is false that this reflection cannot occur while the previous thought is still there. This is because, as we have already seen, the soul is capable of thinking of more than one thing at the same time, and of continuing with a particular thought which it has. It has the power to reflect on its thoughts as often as it likes, and to be aware of its thought in this way...

'But if we did not know that everything real and true within us comes from a perfect and infinite being, then however clear and distinct our ideas were, we would have no reason to be sure that they had the perfection of being true."

If we did not know that all truth has its origin in God, then however clear our ideas were, we would not know that they were true, or that we were not mistaken -I mean, of course, when we were not paying attention to them, and when we merely remembered that we had clearly and distinctly perceived them. For on other occasions, when we do pay atten tion to the truths themselves, even though we may not know God exists, we cannot be in any doubt about them. Otherwise, we could not prove that God exists.
CSMK  353

There may be some doubt here about our reason for suggesting another mode of knowing in addition to intuition, viz. deduction, by which we mean the inference of something as following necessarily from some other propositions which are known with certainty. But this distinction had to be made, since very many facts which are not self-evident are known with certainty, provided they are inferred from true and known principles through a continuous and uninterrupted movement of thought in which each individual proposition is clearly intuited. This is similar to the way in which we know that the last link in a long chain is connected to the first: even if we cannot take in at one 3 70 glance all the intermediate links on which the connection depends, we can. have knowledge of the connection provided we survey the links one after the other, and keep in mind that each link from first to last is attached to its neighbour. Hence we are distinguishing mental intuition from certain deduction on the grounds that we are aware of a movement or a sort of sequence in the latter but not in the former, and also because immediate self-evidence is not required for deduction, as it is for intuition; deduction in a sense gets its certainty from memory. It follows that those propositions which are immediately inferred from first principles can be said to be known in one respect through intuition, and in another respect through deduction. But the first principles themselves are known only through intuition, and the remote conclusions only through deduction. CSM 15 [Rules 3]

It is necessary to observe the points proposed in this Rule if we are to admit as certain those truths which, we said above, are not deduced immediately from first and self-evident principles. For this deduction sometimes requires such a long chain of inferences that when we arrive at such a truth it is not easy to recall the entire route which led us to it. That is why we say that a continuous movement of thought is needed to make good any weakness of memory. If, for example, by way of separate operations, I have come to know first what the relation between the magnitudes A and B is, and then between B and C, and between C and D, and finally between D and E, that does not entail my seeing what the relation is between A and E; and I cannot grasp what the relation is just 388 from those I already know, unless I recall all of them. So I shall run through them several times in a continuous movement of the imagina tion, 'simultaneously intuiting one relation and passing on to the next, until I have learnt to pass from the first to the last so swiftly that memory is left with practically no role to play, and I seem to intuit the whole thing at once. In this way our memory is relieved, the sluggishness of our intelligence redressed, and its capacity in some way enlarged. CSM 25 [Rules 7]