Monday, August 1, 2011

Dreaming scenario vs. the evil demon

To: Paul M.
From: Geoffrey Klempner
Subject: Dreaming scenario vs. the evil demon
Date: 9 February 2004 13:53

Dear Paul,

Thank you for your e-mail of 2 February, with your second timed University of London essay, in response to the exam question, 'The doubt based on dreaming calls as much into question as does the doubt based on a deceiving God. So Descartes has no need to include both in the First Meditation.' Discuss.

My first thought on seeing this was, 'What a great question!' As you will see in what follows, this is a question which would get me working hard in the exam room. I do not have the answer off pat.

As it stands, you have given an excellent answer. I very much liked your use of the distinction between the 'intervention hypothesis' and the 'defective design hypothesis'. Another point in your favour is that you stick closely to the argument of the First Meditation.

I suspect you are wrong about what the question implies. To my ear, the question is completely neutral as to whether the dreaming or deceiving God hypotheses has priority. It merely claims that Descartes 'has no need to include both'. In other words, both hypotheses are equally up for grabs. Dreaming is mentioned first because it occurs first in the text.

However, there is scope here for asking why someone might think that the dreaming hypothesis or the deceiving God hypothesis has priority, looking at plausible arguments for either view and looking for flaws in those arguments.

One thing that occurred to me is that it is worth asking *how* similar are Descartes version of the dreaming hypothesis and the contemporary brain in a vat thought experiment.

The brain in a vat hypothesis requires an external world. 'I' am not at my desk as I thought, but floating in a jar of nutrient. Whereas Descartes' dreaming hypothesis makes no reference to the external scenario. Prior to raising the spectre of a deceiving God, Descartes is prepared to consider that all his experiences arise from himself in some unfathomable way. In other words, for my present experiences to be exactly as they are in their subjective character, there is no logical necessity for an external world of objects in space.

It is also worth noting that Descartes never goes so far as to consider a truly solipsistic view, according to which there is no objective account to be given. His scepticism always assumes that there is something objectively there that ultimately accounts for the character my subjective experiences. He never says, 'Maybe these subjective experiences are *all* there is.'

Maybe this should make us reconsider how important the God story is.

It is tempting to say that so far as the effectiveness of the sceptical hypothesis is concerned, it is irrelevant whether one conceives this as an intelligent agency at work, or blind cause and effect. All the stuff about intervention and defective design serves to make the sceptical hypothesis more vivid, but seeing as we are in the business of being sceptical for scepticism's sake we are not required to tell a story which would render the hypothesis more probable. Judgements of probability have been thrown out the window. All that counts is the bare possibility that I am deceived - never mind who or what might be doing the deceiving.

Continuing this line of thought, the obvious reason that God gets mentioned is the same reason that the evil scientist appears in the brain in a vat hypothesis. It is pretty implausible that brains in vats should have just existed. There is no theory of evolution for brains in vats. But the sceptic isn't asking me to seriously consider the probability that I am a brain in a vat in a Matrix world. Only its logical possibility.

If that's correct (I'm not saying that it is) then there would still be scope for explaining, as you do, why the deceiving God hypothesis suits the purposes of Descartes' exposition of the sceptical case.

In the infamous 'Cartesian Circle', Descartes is accused of relying on his powers of reasoning in order to prove the existence of a benevolent God, whose existence is required in order for reasoning to be reliable. Maybe it suits the evil demon's purposes to make me think there's a God, in which case any attempt to come to any conclusion is invalid. However, Meditation 2 will show that there is one thing that the evil demon *can't* deceive me about. With that established, the door is opened to considering the possibility that some other idea might have the same aura of absolute indubitability - the idea of God or infinite perfection. Once again, however, we don't have to mention an evil demon/ deceiving god here.

One last thought. Could there be a difference between failing to add up 5 and 7 correctly because I have a defective design, and failing to add up 5 and 7 correctly because an intelligent agency is actively seeking to confuse me? If this could be shown, then that might be a case after all for saying that the deceiving God hypothesis is no mere rhetorical device, but demanded by the logic of the argument.

All the best,