Although men may sometimes take a God’s eye view of the universe, they cannot consistently think of themselves as not being covered by any universal account they give of the world or of humanity. For they are men, and live in the world. It is a fair criticism of many philosophies, and not only determinism, that they are hoist with their own petard. The Marxist who says that all ideologies have no independent validity and merely reflect the class interests of those who hold them can be told that in that case his Marxist views merely express the economic interests of his class, and have no more claim to be adjudged true or valid than any other views. So too the Freudian, if he makes out that everybody else’s philosophy is merely the consequence of childhood experiences, is, by parity of reasoning, revealing merely his delayed response to what happened to him when he was a child. So too the determinist. If what he says is true, he says it merely as the result of his heredity and environment, and nothing else.

[I]f there were a drug that caused one to hallucinate one’s doctor calling to say that one was not susceptible to the effects of the drug, presumably doctors would find some other way to inform their patients of their immunity than by calling them on the telephone!

Naive realism leads to physics, and physics, if true, shows that naive realism is false. Therefore, naive realism, if true, is false; therefore it is false.

Scepticism, while logically impeccable, is psychologically impossible, and there is an element of frivolous insincerity in any philosophy which pretends to accept it. Moreover, if scepticism is to be theoretically defensible it must rejectall inferences from what is experienced; a partial scepticism, such as the denial of physical events experienced by no one, or a solipsism which allows events in my future or in my unremembered past, has no logical justification, since it must admit principles of inference which lead to beliefs that it rejects.