748 POPULAR SCIENCE MONTHLY.
tastes, and touches flow round liim in limitless variety. Of many, perhaps of most, he is never conscious ; to only a few does he respond.
Objection may be made to the analogy, but on examination I am sure it will be found to be sufficiently close for our own pur- pose. To the mind, sounds, tastes, colors, odors, and sights are what foods are to the sponge they are stimuli. Specialists on the eye tell us that the range of light vibrations to which the human eye responds is but a little break in a great series, like a short stretch cut out of the middle of an inclined plane. So, too, with our ears. They can intercept only a few of the possible sound vibrations that make up the world of noises. As the sponge, then, comes in contact with but the merest vialful of the great ocean, the human organism also makes contact with mere fragments of the world's infinity of stimuli.
There is a second respect in which the analogy holds good. Just as, out of the limited flow of food-laden sea water that passes its doors, the sponge chooses what it needs, what it can assimilate, so the human organism, out of the limited variety of stimuli to which it is competent to reach, chooses such to respond to as are important.
Now, what has this to do with belief ? Simply this, that belief, whatever else it may be, is a human function, and in so far as it is vital and important it must be subject to the fundamental laws of the organism. We can neither believe nor disbelieve what we never come in contact with, and the stress of life causes us to believe only what is important to us, as the sponge absorbs only what will nourish it. I do not say we are incapable of be- lieving a thing that is useless for us. It is possible for an organ- ism to take and to treat as food that which is valueless. But in the main, life means taking what is good, and taking what is not good means death. This is as true of the mental life as it is of the physical life, and for the most part the process of choice is instinctive and unconscious. When the thermometer falls we have sensations of discomfort we may respond by taking off our clothing. It is conceivable that we should believe it is getting hot. But we do actually respond by putting on our overcoats, which is good evidence that we believe it is cold.
This, I take it, is what Prof. Bain meant when he said, " In its essential character belief is a phase of our active nature," and I do not think it conflicts in any way with Hume's account of belief as a " more vivid, lively, forcible, firm, steady conception than the imagination is able to attain." In fact, both of these accounts seem to me very true. What I mean by believing my friend's word is not that I have a clear perception that his words repre- sent definite things, but that I conceive the main thing he de-