To: Ruy R.
From: Geoffrey Klempner
Subject: Evaluating Descartes' method of doubt
Date: 20th September 2011 15:05

Dear Ruy,

Thank you for your email of 10 September, with your essay (or essay sketch) for the University of London BA Modern Philosophy: Descartes, Spinoza, Leibniz module, in response to the question, 'Why did Descartes choose to begin the Meditations with a method of doubt? Does the doubt go too far, or does it not go far enough?'

There is much room for improvement. You say some of the things that need to be said -- in particular the point about private language is a telling one -- but the essay as a whole is not very persuasive, and lacks any sense of conviction.

Descartes, as you observe, 'brought back to the history of philosophy the central question of knowledge'. That is in itself a remarkable fact. Scepticism had appeared before (in late Greek philosophy). But this scepticism is different. Descartes is sceptical with a purpose.

As you state, Descartes was seeking a 'solid ground' for the 'edifice' of science. But he also announces, in the full title of the Meditations, that '... the existence of God and the distinction of the soul from the body are demonstrated.' Was this just cover, to protect his defence of science from the criticisms of the Church? That's a possible view, but not a very convincing one. Descartes' argument for mind-body dualism is still in one form or other regarded as a challenge today.

Descartes is offering nothing less than a full-blown metaphysic: a theory or definition of the nature of reality, as such, an answer to Aristotle's question about 'Being qua Being'. There are two basic substances, mental substance and material substance, both of which depend for their continued existence on the ever-present creative power of God.

There is a stated aim, right at the beginning of Meditation 1, which we have to read to some extent as heuristic or rhetorical. Yes, up to the time of Descartes there have been disputes about what is known or what can be known. When you cannot find any agreed proposition to start from, you have to retreat, go back to the 'foundations' wherever they may be. So it perfectly suits Descartes' purpose to represent his enterprise as seeking 'indubitable foundations' of knowledge. Something that no-one can dispute. Then, from that basis, an argument which step by step reconstructs the scientific edifice.

I would rather say that Descartes had two aims, in pursuing the method of doubt: to establish a metaphysical theory, and to construct a foundationalist epistemology. The latter aim is one which philosophers have pursued right up to recent times. A.J. Ayer's sense datum theory is one notorious example. (See below.)

As I said, you do mention, although too briefly, key issues regarding the extent of the systematic doubt: the ability to reason, and the possession of language. This poses a problem, however, for understanding the intention of the question. Because one could say that the explanation of why the doubt 'goes too far' and also 'not far enough' is exactly the same in both cases!

The doubt goes too far because Descartes is prepared to doubt the existence of an external world, together with the community of language speakers etc. The doubt does not go far enough because Descartes fails to consider that the ability to reason and employ language itself depends, ultimately, on my belonging to such a community of language users. I think you see this, but you need to state the point more explicitly.

In other words (in my view) this is really a trick question. There really isn't an alternative here. It is not as if some kind of super-Descartes is likely to come along who (with the aid of a conjuring trick) solves the problem of knowledge on an even narrower basis or foundation than Descartes does himself. Although, on reflection, I suppose A.J. Ayer's theory goes further at least in not requiring that sense data logically entail the existence of a subject, the non-physical 'I'. That's a point you could make.

Nor is it a valid option to simply refuse to see the reasons for doubt that Descartes sees. The closest philosopher who takes that view would be someone like G.E. Moore in his 'common sense' defence of knowledge and realism. I just 'know' that I have two hands, and nothing could induce me to doubt that fact. On the contrary, it takes a transcendental argument -- Wittgenstein's argument against a private language -- to establish the a priori necessity of a social context and an external world, in effect, to prove that I have two hands.

I am just gesturing here at the sorts of line that you could explore. I think this is a prime case where you can just attack the question, question the assumptions behind it, and offer your reflections on the shortcomings of Descartes' project.

All the best,

Geoffrey