We saw in the last lecture that the pragmatic method, in its dealings with certain concepts, instead of ending with admiring contemplation, plunges forward into the river of experience with them and prolongs the perspective by their means. Design, free-will, the absolute mind, spirit instead of matter, have for their sole meaning a better promise as to this world's outcome. Be they false or be they true, the meaning of them is this meliorism. I have sometimes thought of the phenomenon called 'total reflexion' in optics as a good symbol of the relation between abstract ideas and concrete realities, as pragmatism conceives it. Hold a tumbler of water a little above your eyes and look up through the water at its surface--or better still look similarly through the flat wall of an aquarium. You will then see an extraordinarily brilliant reflected image say of a candle-flame, or any other clear object, situated on the opposite side of the vessel. No candle-ray, under these circumstances gets beyond the water's surface: every ray is totally reflected back into the depths again. Now let the water represent the world of sensible facts, and let the air above it represent the world of abstract ideas. Both worlds are real, of course, and interact; but they interact only at their boundary, and the locus of everything that lives, and happens to us, so far as full experience goes, is the water. We are like fishes swimming in the sea of sense, bounded above by the superior element, but unable to breathe it pure or penetrate it. We get our oxygen from it, however, we touch it incessantly, now in this part, now in that, and every time we touch it we are reflected back into the water with our course re-determined and re-energized. The abstract ideas of which the air consists, indispensable for life, but irrespirable by themselves, as it were, and only active in their re-directing function. All similes are halting but this one rather takes my fancy. It shows how something, not sufficient for life in itself, may nevertheless be an effective determinant of life elsewhere. In this present hour I wish to illustrate the pragmatic method by one more application. I wish to turn its light upon the ancient problem of 'the one and the many.' I suspect that in but few of you has this problem occasioned sleepless nights, and I should not be astonished if some of you told me it had never vexed you. I myself have come, by long brooding over it, to consider it the most central of all philosophic problems, central because so pregnant. I mean by this that if you know whether a man is a decided monist or a decided pluralist, you perhaps know more about the rest of his opinions than if you give him any other name ending in IST. To believe in the one or in the many, that is the classification with the maximum number of consequences. So bear with me for an hour while I try to inspire you with my own interest in the problem.