It is, indeed, too late in the world's history to try to revive the crude materialism of the past. Whatever else the philosophers have done, they have fixed our attention upon the striking distinction between mental phenomena and physical. He who has once grasped this may be a semi-materialist—an unconscious materialist—as is the plain man to-day, notwithstanding his assertion that the mind is immaterial; and as is his more learned neighbor the 'interactionist' psychologist, of whom I spoke in a recent paper in this journal. But he can scarcely be a materialist out-and-out.
Hence, men have felt impelled to turn to other ways of making clear the relation of mind and body. Some have said that consciousness is a function of the brain; some, that it is the inside of that which, regarded from the outside, is brain-change; some, that it is the reality to which physical phenomena may be referred as appearance.
It is not well to let any one of these statements pass without scrutiny. What do we mean when we say that the mind is a function of the brain? Do we mean only that, given certain changes in the brain, certain mental phenomena come into being? It still remains to ask how the mental phenomena are related to the brain. Are they in there? and if not, where are they? or are they anywhere, in any intelligible sense of the word? The word 'function' is not a word to conjure with. We may call motion a function of brain molecules, if we choose; but evidently a memory or a feeling of pain is not a function of this kind, and the question still confronts us: What kind of a function is it?
As to the statement that mental phenomena may be regarded as the inside of that which, looked at from the outside, is brain-change—this we may take as merely 'a manner of speech,' as a something to say to troublesome persons who ask us difficult questions and must be answered at all hazards. When we say that seeds are inside of an orange, we know what we mean. They are things that occupy space, and can be found in the spaces that they occupy. A leather purse may be lined with silk, and it may contain silver; but try to line a leather purse with painful emotions, and to fill it with hopes and expectations! We play with the words 'inside' and 'outside' when we talk in this way, and it is not proper to play when one is philosophizing, some learned men to the contrary notwithstanding.
Nor should the words 'appearance' and 'reality' be abused recklessly. They have a proper meaning, and we ought to keep to it. We say that a tree seen at a distance looks small, but really is large; and we say that a stick stuck into water looks crooked, but really is straight. Certain experiences we look upon as appearances, and certain others, which for some reason we regard as more satisfactory or more normal,
- Popular Science Monthly, February, 1907.