There can be no doubt that we do know one another. We know that others exist and we know a good deal about others. The question is how we know others. To say that others do not exist would be to assert a solipsism—a theory which no serious philosopher has ever maintained. Solipsism is absurd. Not because it is self-contradictory, for there is nothing self-contradictory in the notion that I alone exist having the experiences and thoughts which I do have and that apart from me nothing and no one else exists. It is absurd simply because others do exist and I know this; because, that is to say, it contradicts the known evidence. This is the sole—but the adequate—ground for concluding solipsism to be absurd. Any discussion of this present problem, therefore, must begin with, the recognition of the fact that knowledge of others occurs.
1 In substance, though considerably altered, this paper is the Dr. Williams Trust Lecture delivered at Carmarthen in October 1942.