Will Large

In this course, we hope to come to some understanding of the roots of what has comes to be called rationalism. We shall do so by investigating and reading in depth in the works of the philosopher Descartes and more specifically the Meditations. Descartes is important because he marks a break with Aristotelian ontology and in so doing ushers in the modern period of philosophy that begins with consciousness, rather than substance. Like every break with a previous metaphysics, or indeed like any new philosophy, Descartes begins with scepticism. From a sophistical point of view, the purpose of scepticism is to destroy the possibility of philosophy. We can already see this at the beginning of Plato’s Theatetus, which portrays, in the clearest fashion, the outline of classical scepticism. It is not possible to trust our senses; therefore, we can have no certain knowledge of the world. Descartes also begins with scepticism about the world, but his aim is not to undermine philosophy, but to build it up again on more secure foundations. This is clear from the architectural metaphor, which is quite famous, that he employs in the Discourse:
Admittedly, we never see people pulling down all the houses of a city for the sole purpose of rebuilding them in a different style to make the streets more attractive; but we do see many individuals having their houses pulled down in order to rebuild them, some even being forced to do so when the houses are in danger of falling down and their foundations are insecure [AT, Vol. VI, p. 13-4].
It is not a question of wholesale destruction, but of rebuilding our knowledge of the world such that scepticism is defeated once and for all. Descartes makes this clear again and again in his reply to the objections to the Meditations. For example, in his reply to Hobbes, in the third set of objections, he argues that his scepticism has three purposes: one, to make a distinction between intellectual and sensory knowledge of things, two, to set up these arguments so that they could be refuted at a later stage in the Meditations and three, that the truths that Descartes does present later are certain, because they cannot be shaken by these ‘metaphysical doubts’ [AT, VII, 171-2]. Scepticism is not employed for its own sake, or even to make philosophy impossible, but on the contrary, to make our knowledge of the world even more certain, by showing that sceptical arguments can be defeated if our metaphysics is robust enough. This exactly the same method that Plato employs in the Theatetus, and indeed we might claim that it is the opening gambit of rationalism as such, since its aim is to show that the sceptical argument against the senses is valid, but that this argument fails because it does not see that our true knowledge of the world is based upon reason and not the senses. The weakness of the senses is made up by the strength of reason, and it is Descartes' aim, like all rationalism; to demonstrate that our scientific understanding of the world has is basis in reason, and not sensible knowledge, as common sense might imagine.

This does not mean that Descartes’ scepticism is exactly the same as classical scepticism. In fact, we might say that it is even more extreme, but his aim is always the same as Plato, to demonstrate that these sceptical arguments are invalid and that our knowledge of the world can have a secure foundation through a rational metaphysics, whose ultimate foundation is the proof of the existence of God. This is why Descartes’ scepticism is not completely identical to classical scepticism. For, as we shall see, he not only doubts the evidence of the senses, but also intellectual knowledge. For Plato, intellectual knowledge might lead to knowledge of God, but does not itself require the proof of the existence of God in order to be valid. It belongs to the ascent of the philosophy from the darkness of the cave to the light of truth. For Descartes, on the contrary, with the proof of the existence of God, even intellectual knowledge, like mathematics, remains uncertain. God is the lynchpin of his metaphysics. This ‘metaphysical doubt’ as Descartes calls it, is something completely different from classical scepticism.

Let us now look at the Meditation 1 in more detail. Again it opens with the metaphor of foundations that runs through out Descartes’ writings:
Some years ago I was struck by the large number of falsehoods that I had accepted as true in my childhood, and by the highly doubtful nature of the whole edifice that I had subsequently based on them. I realised that it was, once in the course of my life, to demolish everything completely and start again from the foundations if I wanted to establish anything at in the sciences that was stable and likely to last [AT VII, p. 17.]
Philosophy already begins with doubt for Descartes not to accept those truths of ‘my childhood’. We are not told what these truths are, but we might hazard a guess that they refer to Descartes’ Scholastic education.  We are also told that these ‘truths’ are of a ‘doubtful nature’ and for this reason we need to completely rebuild the foundations of knowledge. But what is the purpose of this endeavour? It is for the sake of offering a secure foundation to our scientific understanding of the world. The reason why Scholastic philosophy is doubtful is that it cannot offer such a foundation. There is a conflict between the new discoveries of science, discoveries that Descartes himself was a part of, and the old Aristotelian metaphysics. The method of doubt is, therefore, not aimless, and not without context. It aims to offer a secure foundation to the new sciences.

Descartes makes it quite clear how doubt operates: ‘I should hold back my assent from opinions which are not completely certain and indubitable…’ [AT VII, p. 18]. Now this seems simply enough from the beginning, but we have to determine what is obvious and what is not, what can be doubted and what cannot be doubted. For something to be doubted, Descartes argues, I only need the slightest suspicion of it, for I am looking for absolute certainty that can act as the foundation of my scientific understanding of the world. First of all, it might seem that most obvious knowledge that I do have about myself and the world is gained through my senses. Can I not see the objects that are before, and is this not the most certain knowledge that I have. Just as in classical scepticism, Descartes wants us to think again as to whether this sensible knowledge really is as certain and indubitable as we think it might be:
Whatever I have up till now accepted as most true I have acquired either from the senses or through the senses. But from time to time I have found that the senses deceive, and it is prudent never to trust them completely those who have deceived us even once [AT VII, p. 18].
In others words, I know that sometimes what I see is not how things really are (think of Plato’s example of the bent stick in water). It is enough that some times my senses deceive and not all the time, because remember we are looking for absolute and not merely everyday certainty.  But even these example of my senses deceiving me, Descartes argues cannot cause me doubt more obvious things. The fact, for example that I am sitting in this room now, that I am listening to this lecture, and so on. The only people who imagine that these things are not real are madmen. But how can I be certain that all that seems real and vivid to me now is actually not a dream, for have I not had dreams that are equally vivid, where I have been sitting in a room and listening to a lecture, but where in fact there is no room or no lecture. Descartes is not trying to prove that reality is a dream, but that I cannot be absolutely certain that it is not:
As I think about this more clearly, I see plainly that there are never any sure signs by means of which being awake can be distinguished from being asleep. The result is that I begin to feel dazed, and this very feeling only reinforces the notion that I may be asleep [AT VII, p. 19].
But are not the things that are present in dreams actually caused by something real and even if individual things are not real, like the room and the lecture that I am listening to, are not the basics components of reality, which these things are made of, themselves real? What does Descartes mean by the basic components of reality? He means those aspects of reality that are described by science, such as extension, quantity, size, number and place, and which belong universally to all things no matter what they are. Surely I cannot doubt that these exist, even though I might doubt that individual things exist:
The class that appears to include corporeal nature in general, and its extension; the shape of extended things; the quantity, or size and number of these things; the place in which they may exist, the time through which they may endure, and so on [AT VII, p. 20].
Descartes’ point seems to be that even though individual things might be a figment of your imagination, you cannot really know whether the cat is real, the basic nature of matter must be real. You don’t know whether it is a real cat or not, but you know there is stuff over there, that it has a shape, size and quantity. Thus I can doubt the science of particulars, such as astronomy, that describes particular things, but I cannot doubt the abstract sciences like mathematics, for everyone knows that a triangle has 3 sides, and 2+2=4. This is indeed what some one like Plato might say, since mathematics is the ideal of absolute certainty, but here Descartes, if we might put it like this, takes a step beyond classical scepticism by introducing a God who has absolute power to deceive me. What if, Descartes asks, all these ideas that I think are certain, are ideas that God has placed in my mind, but do not correspond with anything in reality?
Any yet firmly rooted in my mind is the long-standing opinion that there is an omnipotent God who made me the kind of creature that I am. How do I know that he has not brought about that there is no earth, no sky, no extended thing, no shape, no size, no place, while at the same time ensuring that all these things appear to me to exist just as they do now [AT VII, p. 21]?
But could not someone reply that even this idea of God could be fiction, so I cannot know whether he had put these false ideas in my mind? But even if we were to accept that this idea of God where a fiction, and therefore that God did not exist, then this would mean that the origin of my own existence would be something less perfect than God.  I must have arrived at my present existence through a chain of events, which must have an origin. If I make this origin less powerful than the absolute power of God, then it is even more likely that I am deceived, since my origin would an imperfection. The closing words of the meditation reinforce the arguments that none of my former beliefs, even what first appeared to be absolute, can be trusted:
I will suppose therefore not God, who is supremely good and the source of truth, but rather some malicious demon of the utmost power and cunning has employed all his energies in order to deceive me. I shall think that the sky, the air, the earth, colours, shapes, sounds and all external things are merely the delusions of dreams which he has devised to ensnare my judgement. I shall consider myself as not having hands or eyes, or flesh, or blood or senses, but as falsely believing that I have all these things [AT VII, pp. 22-3].