I suppose that to nearly everybody who sets himself down to think seriously about the riddle of the Universe there very soon occurs the question whether Materialism may not contain the solution of all difficulties. I think, therefore, our present investigation had better begin with an enquiry whether Materialism can possibly be true. I say 'can be true' rather than 'is true,' because, though dogmatic Materialists are rare, the typical Agnostic is one who is at least inclined to admit the possibility of Materialism, even when he does not, at the bottom of his mind, practically assume its truth. The man who is prepared to exclude even this one theory of the Universe from the category of possible but unprovable theories is not, properly speaking, an Agnostic. To know that Materialism at least is not true is to know something, and something very important, about the ultimate nature of things. I shall not attempt here any very precise definition of what is meant by Materialism. Strictly speaking, it ought to mean the view that nothing really exists but matter. But the existence, in some sense or {6} other, of our sensations and thoughts and emotions is so obvious to Common-sense that such a creed can hardly be explicitly maintained: it is a creed which is refuted in the very act of enunciating it. For practical purposes, therefore, Materialism may be said to be the view that the ultimate basis of all existence is matter; and that thought, feeling, emotion--consciousness of every kind--is merely an effect, a by-product or concomitant, of certain material processes. Now if we are to hold that matter is the only thing which exists, or is the ultimate source of all that exists, we ought to be able to say what matter is. To the unreflecting mind matter seems to be the thing that we are most certain of, the one thing that we know all about. Thought, feeling, will, it may be suggested, are in some sense appearances which (though we can't help having them) might, from the point of view of superior insight, turn out to be mere delusions, or at best entirely unimportant and inconsiderable entities. This attitude of mind has been amusingly satirised by the title of one of Mr. Bradley's philosophical essays--'on the supposed uselessness of the Soul.'[1] In this state of mind matter presents itself as the one solid reality--as something undeniable, something perfectly intelligible, something, too, which is pre-eminently {7} important and respectable; while thinking and feeling and willing, joy and sorrow, hope and aspiration, goodness and badness, if they cannot exactly be got rid of altogether, are, as it were, negligible quantities, which must not be allowed to disturb or interfere with the serious business of the Universe.