To: Max T.
From: Geoffrey Klempner
Subject: Significance of scepticism
Date: 4 February 2002 10:55

Dear Max,

Thank you for e-mail of 22 January, with your second essay for the Introduction to Philosophy program, on 'The Significance of Scepticism".

In the first three paragraphs you carefully different forms of scepticism that have appeared in philosophy, and also the different subject areas in which we make claims to knowledge, where sceptical doubt has been, or might be entertained.

You say, "This paper is concerned with the type of scepticism that says that we can know nothing of the physical world around us - by physical world is meant all those object which one normally senses such as trees, animals, rainbows and mountains."

It is significant that you have chosen the question of our knowledge of the physical world, rather than our knowledge of an *external* world. Bishop Berkeley believed that his philosophy of immaterialism was the best defence against scepticism about our knowledge of the physical world. He would have had no hesitation in asserting that we do have knowledge of such things as "trees, animals, rainbows and mountains". Such empirical knowledge is possible, Berkeley argued, on the condition that we accept the metaphysical theory according to which the things mentioned are all ideas in the mind of God.

This involves the denial that there exists an *external* world concerning which one can raise Descartes' question whether our experiences of things around us are only ideas produced in our minds by some non-physical cause (Descartes' 'evil demon'), or whether those experiences are caused by material things existing in the spatio-temporal reality to which we ourselves belong.

However, we can bracket the Berkeley-Descartes debate by concentrating instead on more moderate versions of scepticism of the 'Matrix' dream-machine variety: i.e. the idea that we might, for all we can prove, be living in a physical world where our experiences are produced by physical means (by wires attached to the brain) but not by our perception of the things around us.

Following Barry Stroud's analysis, you make the point that it is not necessary to *prove* that one is not connected to a dream machine. All one needs to be able to do is 'eliminate' the dream machine hypothesis on the basis of the evidence available. Now, I am assuming that we eliminate a hypothesis, when we are able to put forward a *better* hypothesis, a better explanation. Otherwise, there would be no difference between proving that a hypothesis is false, and eliminating it. The problem is that if we are questioning all our knowledge of the physical world, there is no basis on which we can say whether one hypothesis is 'better' than another. The same point can be made by saying that judgements of probability are relative to prior evidence.

I used to think - though I don't any more - that the point about the approaching car was sufficient to refute this kind of scepticism about the physical world. Belief and doubt have a function which is to enable us to deal with the demands made by the world around us. The thought, 'Maybe I'm attached to a dream machine' has no such function, and is therefore not a meaningful example of something one can doubt.

However, I have now finally come around to the view that there is something fundamentally wrong about the concept 'know' - which does not, however, prevent us from being able to use the word for ordinary purposes. If we follow through the strict logic implied by the concept of 'know', no-one knows anything. What makes the concept useful, however, is that we apply it illogically.

'Know' is by no means unique in this way. Notoriously, it is impossible to give a logic for vague concepts, or indeed any concept whose definition involves fuzzy edges. Yet we 'get along' with vague concepts, indeed it would be impossible to do without them. The problem with 'know' is not that it is vague, but is rather illustrated by various forms of sceptical argument to which, in my view, there is no adequate logical response.

You will find four examples of sceptical argument on my most recent page for my Glass House Philosopher notebook:

http://sophist.co.uk/glasshouse/notebook/page130.html

The only argument which I do not find convincing is Pyrrho's argument (argument 2.) according to which no reason for believing that P can be a 'good' reason. In my view, the problem is not with reason (as Hume was later to claim in his 'Treatise') but rather with this particular concept, the concept, X 'knows' that P.

All the best,

Geoffrey