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Belief that I have hands and Locke on simple ideas


To: Alistair L.
From: Geoffrey Klempner
Subject: Belief that I have hands and Locke on simple ideas
Date: 30th April 2010 11:39

Dear Alistair,

Thank you for your email of 24 April with your one hour timed essays (hand written, scanned) for the University of London Epistemology BA Module, in response to the question, 'Must one have independent grounds for thinking that one has hands? If not, explain why not. If so, explain the consequences for one's belief that one has hands', and also for the Modern Philosophers: Descartes et. al. module, in response to the question, 'What kind of idea is a simple idea, according to Locke?"

I understand that you are under a lot of pressure at the moment. My advice with regard to the examination is that once you are in the examination room, you need to forget about how well or badly your revision has gone. There is everything to play for. Attack the question, be bloody minded, don't just rely on arguments you've memorised -- be prepared to think thoughts you haven't thought before. If things go wrong and the answer doesn't work out the way you'd hoped, say so, and explain why you think that it has gone wrong.


You discuss the 'brain in a vat' scenario and also mention G.E. Moore's famous 'proof' of our knowledge of an external world. However, you don't go into the critique of brain in a vat arguments -- such as Putnam's 'brain in a vat' article, or contemporary discussions of the 'principle of closure', i.e. whether knowledge is 'closed' under entailment. (Just to jog your memory: If I have hands then I am not a brain in a vat. So if I know I have hands I must know that I am not a brain in a vat. But I don't know this. Therefore, I don't know that I have hands.)

However, what you offer instead is a version of the brain in a vat scenario which raises a whole lot of new issues, which deserve to be discussed. Well done for that.

The scenario you describe seems to be a version of the Surrogates movie (2009) The difference, however, is that the surrogate 'you' (the robot facsimile which you control) exists and acts in a world exactly like the world that you inhabited before (without your knowledge) you were envatted. So that when you 'look' at your 'hands', your external robot body really is looking at its hands. Indeed, we can simplify things and make the two worlds the same world. Your friends don't know that they are interacting with the robot AL and not the 'real' AL. So to all intents and purposes, its hands are your hands.

The situation is no different in principle, you say, from the one which actually obtains, where you or I are 'brains' in 'vats' (brains in skulls) which interact with an external world through a reliable causal mechanism. That seems initially plausible.

You go on to say, 'There is a position taken in questions of this type suggest that the reality we exist in would be 'wrong' if it was in some way the product of agencies existing in some other reality. I find this position too narrowly focused on the 'reality' of one particular reality at the expense of others...'.

I would like to have seen this idea developed further. For example, imagine that a famous painter goes blind, and friendly aliens secretly pipe visual experiences directly into the artist's visual cortex, so that he is able to continue painting. The aliens take great care to ensure that the experiences are just what they would be if the artist's eyes were working, but (here comes the catch) it is totally a matter of their free choice whether to do this or not. When he sees a yellow flower, does he 'know' that he is seeing a yellow flower? Your position seems to be that there is knowledge, provided that the causal mechanism is reliable -- even if we have totally false beliefs about the nature of that mechanism.

The alternative view would be that the presence of false assumptions invalidate any claim to knowledge. The problem with this line is that it does rather quickly lead to scepticism. It is impossible to investigate *all* of one's assumptions.

Modern Philosophy

Questions like this are always difficult because the look on the surface to be questions merely about exposition. Once you have stated which kinds of 'idea' are 'simple' according to Locke, what more is there to say?

You do manage to say a bit more: you attempt to put Locke's project within the context of his empiricism and his rejection of 'innate ideas'.

As you remark, Locke's use of the term 'idea' is rather wider than current usage. In fact, not only does Locke talk of 'ideas of sensation', he also describes sensations as 'ideas'. However, we can make some headway by attempting to translate what Locke says into more modern terminology.

As an initial stab, one might say that there are, for Locke, two kinds of concept. Those whose meaning can be explained in terms of other concepts, and those whose meaning can only be grasped ostensively, by having the 'object' which falls under the concept present, and being told, 'That is an example of an F'.

For Locke, examples of these 'objects' are, as you say, very varied. Not only do they include colours, tastes, sounds, feels etc. but also actions of the mind such as 'perception, reasoning, knowing and willing'.

Apart from raising the question whether such things as perception and knowledge can, contra Locke, be defined, the only criticism that you make of Locke's theory is in the very last two sentences. Locke's theory is open to sceptical attack. To make this more explicit, the reason is that for Locke ideas form what has been termed a 'veil of perception' between the mind and the actual world. When I perceive a tree, what my mind actually perceives is a collection of ideas from which I infer the existence of a tree.

However, there is a puzzle here, because this doesn't follow simply from the thesis that there are 'two kinds of concept, those which are defined ostensively and those which are defined in terms of other concepts'. So there is an extra -- very important -- assumption or step here which is needed to get Locke's theory of ideas from the uncontroversial observation that not all concepts can be defined in terms of other concepts, but must be defined ostensively.

Homing in on this point is really the heart of the essay: For Locke, 'ostension' isn't, as one would normally construe it, a matter of persons interacting in an external world, pointing things out to one another, but rather something necessarily internal. We can't take 'the external world' for granted, but have to construct it out of 'ideas'. So ostension becomes a private 'ceremony' which one enacts within the confines of one's own mind. It is this assumption which Wittgenstein's argument against a private language was intended to defeat.

All the best,