Some brains in a vat

Consider the story of the brain in a vat (Pollock: 152-154).

The story of the brain in a vat raises some interesting questions:

1 What is real? (METAPHYSICS)

What would the brain in a vat come to think of as real? Presumably he would think that whatever he experienced was real. Of course he would be mistaken about this. His sense experience does not deliver to him accurate information about the nature of the world.

What does this story suggest about us? We also tend to take to be real just what we have immediate sense experience of. And we are also reluctant to admit as real anything that cannot be immediately experienced.

The story suggests that it may be dangerous for us to think of sense experience

(a) as revealing all there is to reality; and
(b) as revealing the true nature of reality.

2 What can we know? (EPISTEMOLOGY)

How could we know anything beyond sense experience? And how could we know that sense experience is itself reliable? How could we know whether or not reality is coextensive with human sense experience? How could we know whether there are any things which cannot be seen, touched, heard or smelt? What resources have we got?

One answer: we haven’t got anything - our senses are the sole source of knowledge (Empiricism). Sense experience is reliable (it really does give us access to the way things are) and it is exhaustive (there is nothing that is not, in principle, accessible to our sense experience).

But this solution is problematic. For if sense experience is our only source of knowledge then, since we cannot,by sense experience alone, distinguish between a vat-existence and what we take to be our current existence, we cannot know whether sense experience gives us any knowledge at all. That is to say, if empiricism is true then we cannot know that it is true. Empiricism seems to undermine itself.

Another answer: We have reason. Indeed, the little argument I just gave you shows how we can gain some interesting insights by reason alone.

3 What is good? (ETHICS)

Suppose you have a conception of what a good life would be like. Maybe you would like to do Nobel-prize winning work in some discipline like Physics or Economics. Maybe you would like to teach handicapped people. Maybe you would like to write a best-selling novel.

Suppose I now offer you the following deal. If you will donate your brain to scientific research we will place it in a vat and engineer for you the experience of living the very kind of life you would really love to lead. Of course, you would not be leading that life. You would merely be having experiences of leading such a life.

Would the experience of such a life be just as valuable as the life itself? If so you would be crazy to give up the certainty of having such an experience for the fairly low probability of having real experiences which would at best only resemble the kind of life you would like to lead. Moreover, you should be indifferent between the vat-experience and the real-life experience of the same sort.

Not many of us are indifferent. And that tells us something important about what we take to be really valuable.

The little story of the brain in a vat is thus a rich source of questions and insights. These are the sorts of questions and insights which philosophy is about.