The Cartesian Circle

(selections from the Objections and Replies)


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. [Cf. Med. iii, above p.25, marginal number 35-36; Med. v, above p.48, marginal number 70-71.] 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. [Second Objections: CSM II 89, pp. 102-103.]


When I said that we can know nothing for certain until we are aware that God exists, 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 dialecticians...

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 knowledge. 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.  [Second Replies: CSM II 100-101, p. 103.]

There are other truths which are perceived very clearly by our intellect so long as we attend to the arguments on which our knowledge of them depends; and we are therefore incapable of doubting them during this time. But we may forget the arguments in question and later remember simply the conclusions which were deduced from them. The question will now arise as to whether we possess the same firm and immutable convic­tion concerning these conclusions, when we simply recollect that they were previously deduced from quite evident principles (our ability to call them 'conclusions' presupposes such a recollection). My reply is that the required certainty is indeed possessed by those whose knowledge of God enables them to understand that the intellectual faculty which he gave them cannot but tend towards the truth; but the required certainty is not possessed by others. This point was explained so clearly at the end of the Fifth Meditation' that it does not seem necessary to add anything further here. [Second Replies: CSM II 102-5, pp. 105-106.]

I have one further worry, namely how the author avoids reasoning in a circle when he says that we are sure that what we clearly and distinctly perceive is true only because God exists. But we can be sure that God exists only because we clearly and distinctly perceive this. Hence, before we can be sure that God exists, we ought to be able to be sure that whatever we perceive clearly and evidently is true. [Fourth Objections: CSM II 150, p. 106.]


Lastly, as to the fact that 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: I have already given an adequate explanation of this point in my reply to the Second Objections, where I made a distinction between what we in fact perceive clearly and what we remember having perceived clearly on a previous occasion. To begin with, we are sure that God exists because we attend to the arguments which prove this; but subsequently it is enough for us to remember that we perceived something clearly in order for us to be certain that it is true. This would not be sufficient if we did not know that God exists and is not a deceiver.     [Fourth Replies: CSM II 171, p. 106.]


But what about when I was considering something very simple and straightforward in arithmetic or geometry, for example that two and 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 judgment 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 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. 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.  [Third Meditation,  pp. 24-25, nn. 36-36.]

Although it needed close attention for me to perceive this, I am now just as certain of it as I am of everything else which appears most certain. And what is more, I see that the certainty of all other things depends on this, so that without it nothing can ever be perfectly known.

Admittedly my nature is such that so long asI 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 judgment 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 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.

Now, however, I have perceived that God exists, and at the same time I have understood that everything else depends on him, and that he is no deceiver; and I have drawn the conclusion that everything which I clearly and distinctly perceive is of necessity true. Accordingly, even if I am no longer attending to the arguments which led me to judge that this is true, as long as I remember that I clearly and distinctly perceived it, there are no counter-arguments which can be adduced to make me doubt it, but on the contrary I have true and certain knowledge of it. And I have knowledge not just of this matter, but of all matters which I remember ever having demonstrated, in geometry and so on. For what objections can now be raised?That the way I am made makes me prone to frequent error? But I now know that I am incapable of error in those cases where my understanding is transparently clear. Or can it be objected that I have in the past regarded as true and certain many things which I afterwards recognized to he false? But none of these were things which I clearly and distinctly perceived: I was ignorant of this rule for establishing the truth, and believed these things for other reasons which I later discovered to be less reliable. So what is left to say? Can one raise the objection I put to myself a while ago, that I may be dreaming, or that everything which I am now thinking has as little truth as what comes to the mind of one who is asleep? Yet even this does not change anything. For even though I might be dreaming, if there is anything which is evident to my intellect, then it is wholly true.

Thus I see plainly that the certainty and truth of all knowledge depends uniquely on my awareness of the true God, to such an extent that I was in­capable of perfect knowledge about anything else until I became aware of him. And now it is possible for me to achieve full and certain knowledge of countless matters, both concerning God himself and other things whose nature is intellectual, and also concerning the whole of that corpo­real nature which is the subject-matter of pure mathematics.1


1          . . . and also concerning things which belong to corporeal nature in so far as it can serve as the object of geometrical demonstrations which have no concern with whether that object exists' (French version). [Fifth Meditation, pp. 48-9, nn. 69-71.]