Neither position seems a sensible one.  Are we justified in assuming what cannot be proved? or is the argument “from analogy” really a proof of some sort?  Is it right to close our eyes to what “may very well be,” just because we choose to do so?  The fact is that both of these writers had the conviction, shared by us all, that there are other minds, and that we know something about them; and yet neither of them could see that the conviction rested upon an unshakable foundation.

Now, I have no desire to awake in the mind of any one a doubt of the existence of other minds.  But I think we must all admit that the man who recognizes that such minds are not directly perceived, and who harbors doubts as to the nature of the inference which leads to their assumption, may, perhaps, be able to say that he feels certain that there are other minds; but must we not at the same time admit that he is scarcely in a position to say:  it is certain that there are other minds?  The question will keep coming back again:  May there not, after all, be a legitimate doubt on the subject?

To set this question at rest there seems to be only one way, and that is this:  to ascertain the nature of the inference which is made, and to see clearly what can be meant by proof when one is concerned with such matters as these.  If it turns out that we have proof, in the only sense of the word in which it is reasonable to ask for proof, our doubt falls away of itself.

41.  THE ARGUMENT FOR OTHER MINDS.—­I have said early in this volume (section 7) that the plain man perceives that other men act very much as he does, and that he attributes to them minds more or less like his own.  He reasons from like to like—­other bodies present phenomena which, in the case of his own body, he perceives to be indicative of mind, and he accepts them as indicative of mind there also.  The psychologist makes constant use of this inference; indeed, he could not develop his science without it.

John Stuart Mill (1806-1873), whom it is always a pleasure to read because he is so clear and straightforward, presents this argument in the following form:[3]—­

“By what evidence do I know, or by what considerations am I led to believe, that there exist other sentient creatures; that the walking and speaking figures which I see and hear, have sensations and thoughts, or, in other words, possess Minds?  The most strenuous Intuitionist does not include this among the things that I know by direct intuition.  I conclude it from certain things, which my experience of my own states of feeling proves to me to be marks of it.  These marks are of two kinds, antecedent and subsequent; the previous conditions requisite for feeling, and the effects or consequences of it.  I conclude that other human beings have feelings like me, because, first, they have bodies like me, which I know, in my own case, to be the antecedent condition of feelings;