Philosophy

4

LECTURE: Introduction to Descartes

Rationalism versus empiricism

We’ve discussed how early modern thinkers adopted the “mechanical world picture” in place of the Aristotelian understanding of the natural world. You can think of this as a revolution in metaphysics, a revolution in the way people thought about the general structure of reality. There was also, around the same time, a revolution in epistemology, in their thinking about the nature of knowledge. But here there was not one view that replaced the older one associated with Aristotle and Aquinas. There were two main competing candidates: rationalism and empiricism.

Rationalism was the dominant tendency on the European continent. Hence historians of philosophy traditionally speak of “continental rationalism.” The three main thinkers here are Descartes, Spinoza, and Leibniz. Empiricism was the dominant tendency in the British Isles. Hence historians traditionally speak of “British empiricism.” The three main thinkers here are Locke, Berkeley, and Hume.

Marvel’s Civil War, the original line-up

The common and simplest (though in fact oversimplified) way of explaining the difference is to say that rationalists hold that all knowledge is based on what can be known through pure reason apart from the senses, and empiricists hold that all knowledge is based on what can be known through the senses. But there’s a lot more to it than that.

Recall that Aristotelian thinkers like Aquinas were committed to two main claims that are especially relevant here: (a) that nothing can get into the intellect except through the senses, but also (b) that the intellect is to be sharply distinguished from the senses and the imagination.

Rationalists and empiricists each essentially took half of this picture of knowledge while rejecting the other half. The rationalists rejected (a) while keeping (b); the empiricists rejected (b) while keeping (a).

So, rationalism agrees with the Aristotle’s and Aquinas’s point (b) – which, you will recall, is that concepts are radically different from mental images, so that the intellect is therefore radically different from the senses and imagination. But then, the rationalist says, how can we accept (a)? If concepts are so radically different from sensory images, how could it be true that the intellect needs the senses for input?

So, the rationalists end up denying (a). They deny that all concepts have to arise from the senses. Instead, the rationalists adopt the doctrine of innate ideas . This is the claim that certain concepts are innate or built into the human mind even before we have any sensory experience at all. And these innate ideas, they claim, are the necessary starting point or foundation of all knowledge. In that way, the ultimate basis of knowledge, for the rationalists, is not the senses, but rather what pure reason can know even apart from the senses.

Now, the empiricists drew a very different lesson. The empiricists reject the doctrine of innate ideas. They agree with Aristotle and Aquinas about point (a) – that nothing can get into the intellect except through the senses. The foundation of all knowledge, according to the empiricists, must be found in sensory experience.

But in that case, the empiricists say, how can we accept (b)? How could concepts be different from mental images – from faint copies of sensory experiences? So, the empiricists end up rejecting (b). They take the view (either implicitly or explicitly) that a concept is really just a kind of mental image, and that the intellect is really just the same as the imagination. To understand something, on this view, requires being able to form some sensory image.

Enter Descartes

This sets the stage for the “father of modern philosophy,” Rene Descartes (1596-1650). Here he is:

Hi there!

Now, why is he the “father” of modern philosophy, given that there are other early modern thinkers who were writing at the same time or even earlier? There are two main reasons.

First, recall that the Aristotelian system is vast, encompassing theories not only in all the main branches of philosophy, but also in theology and in the various sciences, and having enormous implications for morality, religion, politics, and culture. If one was going to replace it, then – which the early moderns wanted to do – it isn’t enough just to criticize it on this or that particular point. One has to come up with some wholesale replacement, something equally comprehensive, with alternative answers and approaches to the same problems it dealt with.

Descartes’s philosophy was really the first system of thought with the scope to do that. Of the early modern thinkers, he’s really the first who was a contender for being a “new Aristotle” or a “new Aquinas.” (And keep in mind that he was a physicist and mathematician no less than he was a philosopher. So his system of thought had a very wide range.)

The second, and related, reason is that pretty much everything that has happened in philosophy since Descartes’ time has been a reaction to him. Later thinkers either carried forward certain themes originating in Descartes, or they criticized him. But either way, his philosophy effectively set the agenda.

To situate Descartes with respect to the ideas we’ve looked at so far, we can say the following. Like Aristotle and Aquinas, he is a kind of dualist – he thinks human beings are composites of soul and body, of something immaterial and something material. However, he does not spell this out the way Aristotle and Aquinas would. He wants to replace their metaphysics with one inspired by the “mechanical world picture.” He also wants to replace their epistemology, but not in an empiricist way. Rather, he defends a rationalist account of knowledge.

The aims of Descartes’ Meditations

Probably the most famous of Descartes’ works is the Meditations, and that’s the one I have assigned some reading selections from. Let’s begin by noting the general aims of the book. There are six of them. The first two are:

1. To demonstrate the existence of God

2. To establish the real distinction between soul and body

You might think that these aims make Descartes sound like a thinker in the mold of Aristotle and Aquinas, and they are indeed very traditional aims of the sort you would see in a medieval work on metaphysics. But that is precisely part of the point. Descartes puts emphasis on these aspects of his project because they are the aspects that would be least offensive to the tradition he was criticizing, which was dominant at the time he was writing. That is not to say that he is insincere about these aims. On the contrary, we’ll see that aims 1 and 2 are crucial parts of Descartes’ overall system. But he needs to put special emphasis on these in part so as to make it easier for the readers of his day to accept aims 3-6, which are more revolutionary and modern.

From medieval to modern

As we’ll see, he also argues for God and the soul in a way that is very different from the way a thinker like Aristotle or Aquinas would. The next aim is:

3. To lay down the metaphysical foundations for Descartes’ new system of physics

Here Descartes wants to re-interpret physics according to his version of the modern “mechanical world picture” – which, as we’ve seen, involved a replacement of the Aristotelian understanding of nature (in terms of act and potency, the four causes, etc.). Because that general way of understanding the natural world influenced so many other things – from arguments about God’s existence and nature, to human nature, to morality, and so on and on – overthrowing it entailed a potentially very radical intellectual and cultural revolution. So, again, with aims 1 and 2 he is hoping in part to “soften” the blow he’s aiming at the tradition represented by Aristotle and Aquinas.

4. To subject existing knowledge claims to doubt, but then to reconstruct all knowledge on a foundation of truths knowable with certainty

Both parts of this fourth aim are crucial to keep in mind. Some of what Descartes says, especially in Meditation One, might make him sound like a radical skeptic – like someone who thinks we can’t really know anything. That is by no means true. In fact he thinks we can know a lot for certain – including in science, philosophy, religion, and other areas of controversy – but he disagrees with the specific way that Aristotelian thinkers tried to show this. He wants to replace their approach with a different one of his own, which he thinks will provide an absolutely secure and certain basis for knowledge. The next aim is:

5. To refute the Aristotelian and empiricist view that knowledge derives from sensation

Again, Descartes is a rationalist. He thinks that all knowledge must rest on innate ideas, which can be known via pure reason, apart from sensory experience. The Meditations – including the weird skeptical arguments we’ll see in Meditation One – are intended to support this claim. The last aim is:

6. To determine the essence of matter and its qualities

Here Descartes wants to argue that the nature of matter is entirely captured by mathematics (and, as we’ll see, by geometry specifically). And he wants to argue that it is what we have called primary qualities (size, shape, motion, etc.) rather than secondary qualities (color, sound, taste, etc.) that are the qualities matter really has intrinsically. You’ll recall that these are key themes of the “mechanical world picture,” of which Descartes is a proponent.

Next time we’ll see how Descartes begins to carry out these aims in Meditation One.

Here are some optional YouTube videos of a couple of prominent Descartes scholars giving overviews of Descartes’s philosophy:

John Cottingham on Descartes:

https://www.youtube.com/watch?v=abVVKe5zObU

Bernard Williams on Descartes:

https://www.youtube.com/watch?v=iL5FYgRdNDo