PHL302 Background

Ports of Call


Descartes 2

Descartes, Copernicanism and the foundations of knowledge

First sightings

Readings for this part of your journey
Meditation II and the beginning of Meditation III

Meditation II

In this section we are going to explore how Descartes creates a foundation for knowledge in Meditation II, and how he establishes a criterion for certainty, explores the nature of perception and ideas, and proves the existence of God in Meditation III. Having established that the self exists for certain (at least while it is thinking), Descartes goes on to establish that the essence of the self is to be a thinking thing, and that the essence of material objects is to be extended in space (that is to occupy space) and to be flexible and movable. In the begining of Meditation III he reflects on these truths known for certain and argues that they share certain features which can serve as a criterion for certainty.


Descartes and the condemnation of Galileo

Galileo was the most notable defender of the Copernican system in Europe. There are debates among scholars about Galileo's motives which are similar to the debates about Descartes' motives. Some scholars see Galileo as a Copernican zealot who, without adequate scientific evidence, battled for the Copernican system against reactionary Church authorities. On another, though similar view, Galileo is an irresponsible troublemaker who injured the cause of science by taunting the authorities responsible for maintaing social order. Stillman Drake has offered yet another hypothesis: "Galileo was a zealot not for Copernican astronomy, but for the future of the Catholic Church and for the protection of religious faith against any scientific discove ry that might be made." Drake offers persuasive evidence on behalf of this hypothesis.

Still, Galileo did defend Copernicanism, and given the difficulty of telling which of the two hypotheses was best supported by the evidence, arguments were needed to prove the superiority of the Copernican system. Galileo worked at providing these arguments through much of Descartes' early career --from 1610 until the 1630. His report of his telescopic observations in the Starry Messanger was one of his first efforts in this direction. He eventually produced a work which gave natural philosophical arguments for Copernicanism. These arguments were contained in a book called Dialogue Concerning the Two Chief World Systems. Galileo used the theory of the tides, the movement of sunspots, and a doctrine of inertia in which motions in which one shares (such as the Earth's rotation and motion around the sun) are undetectable. The most important of these arguments had to do with the theory of the tides. He considered these arguments so important that the original title of the Dialogue was The Ebb and Flow of the Tides. The change in title was one of the compromises which Galileo made with the Roman censors. It looked like a series of similar compromises would allow the book to be published. There was, however, a change in political climate, and as a result the book was condemned.

Descartes learned of the condemnation of Galileo's book as he was arranging to publish Le Monde (The World). He wrote to Mersenne:

I had intented to send you Le Monde as a New Year gift...but in the meantime I tried to find out in Leiden and Amsterdam whether Galileo World System was available, as I thought I had heard that it was published in Italy last year. I was told that it had indeed been published, but that all copies had been burned at Rome, and that Galileo had been convicted and fined. I was so surprised by this that I nearly decided to burn all my papers, or at least let no one see them. For I couldn't imagine that he--an Italian and, I believe, in favor with the Pope--could have been made a criminal, just because he tried, as he certainly did, to establish that the earth moves...I must admit that if this view is false, then so too are the entire foundations of my philosophy, for it can be demonstrated from them quite clearly. And it is so integral to my treatise that I couldn't remove it without making the whole work defective. But for all that, I wouldn't want to publish a discourse which had a single word that the Church disapproved of; so I prefer to suppress it rather than to publish it in a mutilated form.

Note that the 'foundations' which Descartes is talking about here are not the foundations provided in the Meditations but rather the principles of Descartes' physics. So, the problem presented to Descartes by the condemnation of Galileo is this. On the one hand he was a committed Copernican -- he believed that the earth moves. On the other hand, he was a committed Catholic, and the Church was now officially on record as condemning the doctrine of Copernicus. What was Descartes to do?

Descartes was clearly devastated by the condemnation of Galileo and the course of his career changed at this point. Previously he had shown some interest in methahysics, he had been largely engaged in natural philosophy. Galileo had given natural philosophical arguments on behalf of Copernicanism. Now, with the condemnation, such arguments were no longer appropriate.

Descartes was also unlikely to accept Fiedism -- the view that skepticism shows that faith and not reason or the senses is the only proper approach to religious knowledge. This was in part because mechanism was incompatible with the kinds of traditional sources of faith, from the Bible to the Christian teachings as set out by the scholastic philosophers. This was true even of Father Mersene, who was orthodox in religious matters.

One possibility is that Descartes wanted to put his own mechanistic system, and thus Copernicanism, on such a certain foundation, that it would not be a matter of faith, but something which is known by reason. Descartes, while intensely religious, had a clear place for reason in his philosophy.

Is there evidence which suggests that Descartes is attempting to provide foundations for his physical system in the Meditations? There is some reason to think this is correct. Part of the argument which Descartes is making in the Meditations is against atomism. Atomism holds that there are two basic components of the universe -- atoms and the void in which the atoms move. Descartes' rejection of atomism is crucial to the physical system which he had worked out in Le Monde. Descartes holds that the universe is entirely filled with matter, and that there is no void space. He is a plenum theorist, rather than an atomist. ('Plenum' means 'full').The debate over whether a vacume existed was a live one for Descartes, sharpened by the development of thermometers, barometers and the air pump, which could remove the air from a glass tube, for example. In the Meditations Descartes rejects the vacume and atomism with it.

In Descartes' theory, matter is composed of three different kinds, rarified, more dense, and most dense. If the universe is filled with matter, how can anything move? In atomic theories, it is precisely the role of the void to provide empty space through which matter can move. Descartes answer is that movement occurs by matter pushing other matter. All matter moves in votices (a vortex is like a whirlpool) and the denser kinds of matter move through the less dense forms of matter. It turns out that from this starting point, given Descartes' laws of motion, he can deduce a Copernican world system. So, if it turns out that one can know for certain that material things are extended, and that there is no void, then Descartes would be a long way towards putting his physical system on a certain foundation.

How does the argument against atomism go? In Meditation II, after having proved that the self exists and going on to argue that its essence is to be a thinking thing, Descartes turns to our knowledge of the external world. He argues that we do have certain knowledge of the essence of material things on the basis of reason alone. We will consider this argument in more detail in the Commentary section. For present purposes, it is simply worth noting that he meditates on the nature of a piece of wax in order to come to demonstrate that the essence of physical objects is known by reason and not by the senses. He argues that the nature of the wax is to be flexible, movable and extended, that is to occupy space. He does not add a characteristic like 'solidity' which would distinguish a solid atom from the void (as we shall find Locke doing later). Later in Meditation VI he claims that there are some things which he thought were taught to him by nature, but which turned out to have been accepted "out of habit of thoughtless judgement" which may well be false. The first example he gives of these is that "that a space is empty if nothing in it happens to affect my senses." (Rubin, Pg. 47) So matter is extended, and there is no void. These reflections may show us just how important Descartes regards putting knowledge of the external world (and indeed knowledge of the basic features of his own mechanistic system) on a secure foundation.


  1 of 5   NEXT