To: Diane F.
From: Geoffrey Klempner
Subject: The significance of philosophical scepticism
Date: 12 February 2008 11:51

Dear Diane,

Thank you for your email of 28 January, with your second essay for the Possible World Machine, entitled 'The Significance of Philosophical Scepticism.'

This is a good essay. I have the impression that you sat down and pondered the question of significance and came up with, not one but several equally valid answers. This suggests that we should be cautious in talking of 'the' significance of philosophical scepticism.

What is significance? That is a philosophical question in its own right. Scepticism might be significant as a symptom of some kind of error or illusion. Or, it might be a necessary corollary of what you describe as 'a compulsion to know, to seek knowledge'. Or, it might be rooted in contingent historical circumstances which might, had the course of history taken a different turn, have been otherwise.

What is it that the sceptic claims? You say, 'Extreme scepticism claims that nothing is certain.' However, it looks as though a possible reply would simply be to say that knowledge doesn't require 'absolute certainty'. I know I am writing this email to you even though I can imagine that this is exactly how things would seem if I was in the Matrix. Can I still say I am 'certain'? Well, maybe yes if certainty is ultimately a mental attitude tied to action. There is nothing I can do to 'exhibit' my slight 'uncertainty'. On the other hand, if we are defining certainty as the impossibility of an alternative, then it seems that I cannot be 'certain' in this sense that I am writing this email. There is a possible alternative, however improbable it may seem at this moment.

So there is something to say here about our notion of what is required for 'knowledge'. It could be (as some critics of Descartes have argued) that scepticism is the inevitable result of setting the bar for knowledge too high. Descartes wrongly equates knowledge with certainty. That would be a possible answer to the question of 'significance'.

Going back to historical roots, you suggest in your account of Pyrrhonian scepticism that the sceptics sought to oppose 'the dogmatists'. Was this a problem then, but not now? Did the ancient sceptics succeed in making their point? what was the point anyway?

It is said that the ancient sceptics 'missed' a point that Descartes grasped. While the Pyrrhonians based their claim merely on the observation that equally valid arguments can be presented for opposite conclusions, Descartes focused on foundational questions, arguing that any structure of beliefs which rests on premisses or foundations whose truth can be doubted, cannot stand. If this is right, then this answers the question about certainty I raised above. Descartes is not claiming that all knowledge is 'certain' but only that there must be something certain at the base of knowledge, for there to be any knowledge at all.

As you point out, Descartes was arguably wrong in thinking that he was justified in claiming certainty for his statement, 'I exist.' This does not necessarily wreck the foundational enterprise, however. A.J. Ayer, at least in his earlier years, is an example of an epistemologist who looked to individual experiences as the certain foundation for empirical knowledge (see his 'Foundations of Empirical Knowledge').

Cartesian epistemology gave birth to Cartesian dualism, which as you note may be seen as an impetus for the science of psychology. This is 'significance' in a different sense from what we have considered up to now, a kind of significance which a historian of ideas would be interested in.

Finally, you come to the question of the coherence of scepticism itself. This is the deepest question one can raise about its significance. Is scepticism valid? Or, as the argument about logic seems to suggest, is it self-refuting?

Hume argues at the end of the section of his 'Treatise of Human Nature' entitled, 'On scepticism with regard to the senses' that there is no rational response to extreme scepticism with regard to knowledge of the external world. The only thing left to do is leave philosophical speculation behind. So he goes off to play a game of backgammon. What kind of response is this? It is different, arguably more radical, then anything we have considered up to this point. Humean scepticism was designed to make way for his 'science of human nature' which would reduce epistemology to psychology, his associationist theory of 'ideas and impressions'.

That conclusion is not so very different from the conclusion reached by philosophers like W.V.O. Quine who argue for a 'naturalized epistemology' which rejects altogether foundational questions in favour of scientific inquiry into the way human beings have evolved into beings capable of forming beliefs and constructing theories.

Epistemologists still ask, 'How do you know?' This is not necessarily a sceptical question. It is something we naturally do. You tell me that there's a hurricane coming and I ask you how you know, expecting an answer. The last thing I want to hear is, 'No-one ever knows whether or not a hurricane is coming.'

All the best,

Geoffrey