ABSTRACT
The postulates hitherto considered have been such as are required for knowledge of the physical world. Broadly speaking, they have led us to admit a certain degree of knowledge as to the space-time structure of the physical world, while leaving us completely agnostic as regards its qualitative character. But where other human beings are concerned, we feel that we know more than this; we are convinced that other people have thoughts and feelings that are qualitatively fairly similar to our own. We are not content to think that we know only the space-time structure of our friends’ minds, or their capacity for initiating causal chains that end in sensations of our own. A philosopher might pretend to think that he knew only this, but let him get cross with his wife and you will see that he does not regard her as a mere spatio-temporal edifice of which he knows the logical properties but not a glimmer of the intrinsic character. We are therefore justified in inferring that his scepticism is professional rather than sincere.
