But, if I am asked to justify my belief that other selves, beside my own, are in the world, the answer must be this. I arrive at other souls by means of other bodies, and the argument starts from the ground of my own body. My own body is one of the groups which are formed in my experience. And it is connected, immediately and specially, with pleasure and pain, and again with sensations and volitions, as no other group can be.[1] But, since there are other groups like my body, these must also be qualified by similar attendants.[2] With my feelings and my volitions these groups cannot correspond. For they are usually irrelevant and indifferent, and often even hostile; and they enter into collision with one another and with my body. Therefore these foreign bodies have, each of them, a foreign self of its own. This is briefly the argument, and it seems to me to be practically valid. It falls short, indeed, of demonstration in the following way. The identity in the bodies is, in the first place, not exact, but in various degrees fails to reach completeness. And further, even so far as the identity is perfect, its consequence might be modified by additional conditions. And hence the other soul might so materially differ from my own, that I should hesitate, perhaps, to give it the name of soul.[3] But still the argument, though not strict proof, seems sufficiently good.
It is by the same kind of argument that we reach our own past and future. And here Solipsism, in objecting to the existence of other selves, is unawares attempting to commit suicide. For my past self, also, is arrived at only by a process of inference, and by a process which also itself is fallible.
