17 June 1997
Thank you for your letter of 8 June, with your essay on units 4-6 of Reasons, Values and Conduct, on the question of solipsism.
In the light of the issues you raise, I think it would be worth looking back at the relevant units of The Ultimate Nature of Things for the discussion of what we can conclude from the refutation of subjectivism/solipsism. (I apologise for not being consistent in my terminology, by the way! I still haven't made up my mind which is the best term to use. But 'solipsism' is potentially less confusing in the context where one talks of moral subjectivism and objectivism.) The main difference now in the ethics programme is that I attempt to go further, beyond anti-subjectivism/anti-solipsism, to produce a 'synthesis' that recognises the reality of both egocentric and nonegocentric views. However, for the purposes of the present discussion that development may be ignored. Let's concentrate on just what is involved in rejecting solipsism.
First, we need to get right out of the way worries about whether my subjective experience of the taste of chocolate is changing over time. The transcendental solipsist the solipsist who has learned from Kant's 'Refutation of Idealism' rejects the idea of a 'private object' whose qualities or changes have no consequences for an external world. The transcendental solipsist's 'external world' is a world of objects fit for forming judgements about: for example, the physical stuff I call chocolate. (Of course we remember all the while that all this is just a 'theory', that ultimately there is only this. But Kant's point is that this can only be coherently described in objective terms.)
I can be wrong about whether something is chocolate. It may be synthetic chocolate. That is something which I am perfectly equipped, in principle, to find out, say, by conducting a chemical analysis. As to irrecoverable facts about the past, they remain for the anti-solipsist every bit as much as for the solipsist an open, 'undecidable' question. To imply that as a solipsist all I have to go by is my own impression of the taste is therefore to miss the point. Every means of empirical investigation, including asking others including the relevant experts is available as much to the solipsist as to the anti-solipsist!
Part of the potential confusion here lies in the temptation to present the issue of solipsism and anti-solipsism in sceptical terms. ('How do I/we know that....?') Ultimately, I can be wrong in believing that I am one of several hundred persons working in the University Arts Tower. Perhaps I am the last human being alive, asleep on a laboratory bench in far Andromeda, having experiences fed into my brain. Or we can all be wrong in thinking that we are inhabitants of the planet Earth, orbiting a minor star we call 'the sun'. (I leave you to think up the appropriate scenario.) But that is not the question at issue, the metaphysical question. The metaphysical question is whether, ultimately, what there is (whatever that may be) necessarily exists for just this perspective, or whether it is presented, or at least capable of being presented, to a plurality of perspectives. (Alone in the computer room, it is just possible for me to imagine that I am the last conscious being left alive in the universe. To reject solipsism in this context is to believe in the possibility of perspectives other than my perspective.)
The refutation of solipsism is the refutation of the claim that there ultimately cannot be any perspective other than my perspective, the claim that all my talk of other subjects, other 'perspectives' is ultimately talk about 'characters in the story of my world'.