[Whether God's essence implies his existence]

You next attempt to demonstrate the existence of God, and the thrust of your argument is contained in the following passage:

When I concentrate, it is quite evident that existence can no more be separated from the essence of God than the fact that its three angles equal two right angles can be separated from the essence of a triangle, or than the idea of a mountain can be separated from the idea of a valley. Hence it is just as much of a contradiction to think of God (that is, a supremely perfect being) lacking existence (that is, lacking a perfection) as it is to think of a mountain without a valley.

But we must note here that the kind of comparison you make is not wholly fair.

It is quite all right for you to compare essence with essence, but instead of going on to compare existence with existence or a property with a property, you compare existence with a property. It seems that you should have said that omnipotence, for example, can no more be separated from the essence of God than the fact that its angles equal two right angles can be separated from the essence of a triangle. Or, at any rate, you should have said that the existence of God can no more be separated from his essence than the existence of a triangle can be separated from its essence. If you had done this, both your comparisons would have been satisfactory, and I would have granted you not only the first one but the second one as well. But you would not for all that have established that God necessarily exists, since a triangle does not necessarily exist either, even though its essence and existence cannot in actual fact be separated. Real separation is impossible no matter how much the mind may separate them or think of them apart from each other – as indeed it can even in the case of God's essence and existence.

[Cogito ergo sum (‘I am thinking, therefore I exist’)]

I see that you conclude that this proposition, I am, I exist, is true whenever it is put forward by you or conceived in your mind. But I do not see that you needed all this apparatus, when on other grounds you were certain, and it was true, that you existed. You could have made the same inference from any one of your other actions, since it is known by the natural light that whatever acts exists. [Fifth Objections: CSM II 180]

When you say that I ‘could have made the same inference from any one of my other actions’ you are far from the truth, since I am not wholly certain of any of my actions, with the sole exception of thought (in using the word ‘certain’ I am referring to metaphysical certainty, which is the sole issue at this point). I may not, for example, make the inference Ί am walking, therefore I exist’, except in so far as the awareness of walking is a thought. The inference is certain only if applied to this awareness, and not to the movement of the body which sometimes – in the case of dreams – is not occurring at all, despite the fact that I seem to myself to be walking. Hence from the fact that I think I am walking I can very well infer the existence of a mind which has this thought, but not the existence of a body that walks. And the same applies in other cases. [Fifth Replies: CSM II 244]

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 without existing.

[The real distinction between mind and body]

It is clear that the question he promised to answer still remains outstanding: how does it follow, from the fact that he is aware of nothing else belonging to his essence, that nothing else does in fact belong to it? I must confess that I am somewhat slow, but I have been unable to find anywhere in the Second Meditation an answer to this question. As far as I can gather, however, the author does attempt a proof of this claim in the Sixth Meditation, since he takes it to depend on his having clear knowledge of God, which he had not yet arrived at in the Second Meditation. This is how the proof goes:

We must pause a little here, for it seems to me that in these few words lies the crux of the whole difficulty.

First of all, if the major premiss of this syllogism is to be true, it must be taken to apply not to any kind of knowledge of a thing, nor even to clear and distinct knowledge; it must apply solely to knowledge which is adequate.

I have a very good reason for offering this book to you, and I am confident that you will have an equally good reason for giving it your protection once you understand the principle behind my undertaking; so much so, that my best way of commending it to you will be to tell you briefly of the goal which I shall be aiming at in the book.

I have always thought that two topics – namely God and the soul – are prime examples of subjects where demonstrative proofs ought to be given with the aid of philosophy rather than theology. For us who are believers, it is enough to accept on faith that the human soul does not die with the body, and that God exists; but in the case of unbelievers, it seems that there is no religion, and practically no moral virtue, that they can be persuaded to adopt until these two truths are proved to them by natural reason. And since in this life the rewards offered to vice are often greater than the rewards of virtue, few people would prefer what is right to what is expedient if they did not fear God or have the expectation of an after-life. It is of course quite true that we must believe in the existence of God because it is a doctrine of Holy Scripture, and conversely, that we must believe Holy Scripture because it comes from God; for since faith is the gift of God, he who gives us grace to believe other things can also give us grace to believe that he exists. But this argument cannot be put to unbelievers because they would judge it to be circular. Moreover, I have noticed both that you and all other theologians assert that the existence of God is capable of proof by natural reason, and also that the inference from Holy Scripture is that the knowledge of God is easier to acquire than the knowledge we have of many created things – so easy, indeed, that those who do not acquire it are at fault.

There are many matters which remain to be investigated concerning the attributes of God and the nature of myself, or my mind; and perhaps I shall take these up at another time. But now that I have seen what to do and what to avoid in order to reach the truth, the most pressing task seems to be to try to escape from the doubts into which I fell a few days ago, and see whether any certainty can be achieved regarding material objects.

But before I inquire whether any such things exist outside me, I must consider the ideas of these things, in so far as they exist in my thought, and see which of them are distinct, and which confused.

Quantity, for example, or ‘continuous’ quantity as the philosophers commonly call it, is something I distinctly imagine. That is, I distinctly imagine the extension of the quantity (or rather of the thing which is quantified) in length, breadth and depth. I also enumerate various parts of the thing, and to these parts I assign various sizes, shapes, positions and local motions; and to the motions I assign various durations.

Not only are all these things very well known and transparent to me when regarded in this general way, but in addition there are countless particular features regarding shapes, number, motion and so on, which I perceive when I give them my attention. And the truth of these matters is so open and so much in harmony with my nature, that on first discovering them it seems that I am not so much learning something new as remembering what I knew before; or it seems like noticing for the first time things which were long present within me although I had never turned my mental gaze on them before.

But I think the most important consideration at this point is that I find within me countless ideas of things which even though they may not exist anywhere outside me still cannot be called nothing; for although in a sense they can be thought of at will, they are not my invention but have their own true and immutable natures.

[The rejection of previous beliefs]

[It is objected that] I am asking for something impossible in wanting us to give up every kind of preconceived opinion … But [my critic] has not realized that the term ‘preconceived opinion’ applies not to all the notions which are in our mind (which I admit it is impossible for us to get rid of) but only to all the opinions which we have continued to accept as a result of the previous judgements that we have made. And since making or not making a judgement is an act of will (as I have explained in the appropriate place) it is evident that it is something in our power. For, after all, in order to get rid of every kind of preconceived opinion, all we need to do is resolve not to affirm or deny anything that we have previously affirmed or denied until we have examined it afresh. But this does not entail that we cease to retain all the same notions in our memory. Nevertheless, I did say that there was some difficulty expelling from our belief everything we have previously accepted. One reason for this is that before we can decide to doubt, we need some reason for doubting; and that is why in my First Meditation I put forward the principal reasons for doubt. Another reason is that no matter how much we resolved not to assert or deny anything, we easily forget our resolution afterwards if we have not strongly impressed it on our memory; and this is why I suggested that we should think about it very carefully. [Appendix to Fifth Objections and Replies: CSM II 270]

Here I shall employ an everyday example to explain to my critic the rationale for my procedure, so as to prevent him misunderstanding it, or having the gall to pretend he does not understand it, in future. Suppose he had a basket full of apples and, being worried that some of the apples were rotten, wanted to take out the rotten ones to prevent the rot spreading. How would he proceed? Would he not begin by tipping the whole lot out of the basket?

So serious are the doubts into which I have been thrown as a result of yesterday's meditation that I can neither put them out of my mind nor see any way of resolving them. It feels as if I have fallen unexpectedly into a deep whirlpool which tumbles me around so that I can neither stand on the bottom nor swim up to the top. Nevertheless I will make an effort and once more attempt the same path which I started on yesterday. Anything which admits of the slightest doubt I will set aside just as if I had found it to be wholly false; and I will proceed in this way until I recognize something certain, or, if nothing else, until I at least recognize for certain that there is no certainty. Archimedes used to demand just one firm and immovable point in order to shift the entire earth; so I too can hope for great things if I manage to find just one thing, however slight, that is certain and unshakeable.

I will suppose then, that everything I see is spurious. I will believe that my memory tells me lies, and that none of the things that it reports ever happened. I have no senses. Body, shape, extension, movement and place are chimeras. So what remains true? Perhaps just the one fact that nothing is certain.

Yet apart from everything I have just listed, how do I know that there is not something else which does not allow even the slightest occasion for doubt? Is there not a God, or whatever I may call him, who puts into me the thoughts I am now having? But why do I think this, since I myself may perhaps be the author of these thoughts? In that case am not I, at least, something? But I have just said that I have no senses and no body. This is the sticking point: what follows from this? Am I not so bound up with a body and with senses that I cannot exist without them? But I have convinced myself that there is absolutely nothing in the world, no sky, no earth, no minds, no bodies. Does it now follow that I too do not exist?