of Synopsis the following six Meditations
In the First Meditation reasons are provided which give us possible grounds for doubt about all things, especially material things, so long as we have no foundations for the sciences other than those which we have had up till now. Although the usefulness of such extensive doubt is not apparent at first sight, its greatest benefit lies in freeing us from all our preconceived opinions, and providing the easiest route by which the mind may be led away from the senses. The eventual result of this doubt is to make it impossible for us to have any further doubts about what we subsequently discover to be true. In the Second Meditation, the mind uses its own freedom and supposes the non-existence of all the things about whose existence it can have even the slightest doubt; and in so doing the mind notices that it is impossible that it should not itself exist during this time. This exercise is also of the greatest benefit, since it enables the mind to distinguish without difficulty what belongs to itself, i.e. To an intellectual nature, from what belongs to the body. But since some people may perhaps expect arguments for the immortality of the soul in this section, I think they should be warned here and now that I have tried not to put down anything which I could not precisely demonstrate. Hence the only order which I could follow was that normally employed by geometers, namely to set out all the premises on which a desired proposition depends, before drawing any conclusions about it. Now the first and most important prerequisite for knowledge of the immortality of the soul is for us to form a concept of the soul which is as clear as possible and is also quite distinct from every concept of body; and that is just what has been done in this section. A further requirement is that we should know that everything that we clearly and distinctly understand is true in a way which corresponds exactly to our understanding of it; but it was not possible to prove this before the Fourth Meditation. In addition we need to have a distinct concept of corporeal nature, and this is developed partly in the Second Meditation itself, and partly in the Fifth and Six Meditations. The inference to be drawn from these results is that all the things that we clearly and distinctly conceive of as different substances (as we do in the case of mind and body) are in fact substances which are really distinct one from the other; and this conclusion is drawn in the Sixth Meditation. This conclusion is confirmed in the same Meditation by the fact that we cannot understand a body except as being divisible, while by contrast we cannot understand a mind except as being indivisible. For we cannot conceive of half of a mind, while we can always conceive of half of a body, however small; and this leads us to recognize that the natures of mind and body are not only different, but in some way opposite. But I have not pursued this topic any further in this book, because these arguments are enough to show that they decay of the body does not imply the destruction of the mind, and are hence enough to give mortals the hope of an after-life, and secondly because the premises which lead to the conclusion that the soul is immortal depend on an account of the whole of physics. This is required for two reasons. First, we need to know that absolutely all substances, or things which must be created by God in order to exist, are by their nature incorruptible and cannot ever cease to exist unless they are reduced to nothingness by God's denying his concurrence (The continuous divine action necessary to maintain things in existence) to them. Secondly, we need to recognize that body, taken in the general sense, is a substance, so that it too never perishes. But the human body, in so far as it differs from other bodies, is simply made up of a certain configuration of limbs and other accidents (Descartes here uses this scholastic term to refer to those features of a thing which may alter, e.g. the particular size, shape, etc. of a body, or the particular thoughts, desires, etc. of a mind) of this sort; whereas human the mind is not made up of any accidents in this way, but is a pure substance. For even if all the accidents of the mind change, so that it has different objects of the understanding and different desires and sensations, it does not on that account become a different mind; whereas a human body loses its identity merely as a result of a change in the shape of some of its parts. And it follows from this that while the body can very easily perish, the mind
(Added in French version "... or the soul of man, for I take no distinction between them) is immortal by its very nature. In the Third Meditation I have explained quite fully enough, I think, my principal argument for proving the existence of God. But in order to draw my readers' minds away from the senses as far as possible, I was not willing to use any comparison taken from bodily things. So it may be that many obscurities remain; but I hope they will be completely removed later, in my Replies to the Objections. One such problem, among others, is how the idea of a supremely perfect being, which is in us, possesses so much objective (For Descartes' use of the this term, see the Third Meditation) reality that it can come only from a cause which is supremely perfect. In the Replies this is illustrated by the comparison of a very perfect machine, the idea of which is in the mind of some engineer. Just as the objective intricacy belonging to the idea must have some cause, namely the scientific knowledge of the engineer, or of someone else who passed the idea on to him, so the idea of God which is in us must have God himself as its cause. In the Fourth Meditation it is proved that everything that we clearly and distinctly perceive is true, and I also explain what the nature of falsity consists in. These results need to be known both in order to confirm what has gone before and also to make intelligible what is to come later. But here it should be noted in passing that I do not deal at all with sin, i.e. the error which is committed in pursuing good and evil, but only with the error that occurs in distinguishing truth from falsehood. And there is no discussion of matters pertaining to faith or the conduct of life, but simply of speculative truths which are known solely by means of the natural light (Descartes added this passage on the advice of Arnauld. He told Mersenne "Put the words between brackets so that it can be seen that they have been added" in a letter of 18 March 1641). In the Fifth Meditation, besides an account of corporeal nature taken in general, there is a new argument demonstrating the existence of God. Again, several difficulties may arise here, but these are resolved later in the Replies to the Objections. Finally I explain the sense in which it is true that the certainty even of geometrical demonstrations depends on the knowledge of God. Lastly, in the Sixth Meditation, the intellect is distinguished from the imagination; the criteria for this distinction are explained; the mind is proved to be really distinct from the body, but is shown, not withstanding, to be so closely joined to it that the mind and the body make up a kind of unit; there is a survey of all the errors which commonly come from the senses, and an explanation of how they may be avoided; and, lastly, there is a presentation of all the arguments which enable the existence of material things to be inferred. The great benefit of these arguments is not, in my view, that they prove what they establish namely that there really is a world, and that human beings have bodies and so on since no sane person has ever seriously doubted these things. The point is that in considering these arguments we come to realize that they are not as solid or as transparent as the arguments which lead s to knowledge of our own minds and of God, so that the latter are the most certain and evident of all possible objects of knowledge for the human intellect. Indeed, this is the one thing that I set myself to prove in these Meditations. And for that reason I will not now go over the various other issues in the book which are dealt with as they come up.