The suggestion, then, that the chess-men may be moved with a purpose is not rejected, but is set aside as useless for a scientific comprehension of the game. Invisible agents--and we are all invisible, though our bodies are not--moving the chess-men with a purpose, or cross-purposes, are hypotheses valueless for science, which aims only at positive facts, the laws according to which the pieces actually do move. By the aid of these laws our philosopher might succeed in reconstructing the past history of the game which he was watching. From the positions occupied by the pieces now he might infer the positions from which they came (or think he could), and so back, step by step, until he reached the order in which the pieces are arranged at the beginning of a game. When he reviewed the knowledge thus obtained he would see in the process of the game a certain evolution from the relatively simple movements of the pawns which began the game to the highly complex movements of the queen. Then, whatever the order in which the pieces happened to be brought out and their qualities developed in the particular game he was watching, he might argue on the theory of necessity that that was the only order in which those properties could have been evolved. On the principle that efficient and mechanical causes were sufficient to provide a scientific explanation of the game it would follow that the higher powers manifested by castles and queens, the latest pieces to come out into the game, were caused by the previous action and movements of the less highly developed pawns--that life and consciousness are due to material causes. The idea that the movements of queens and pawns alike were due to the will of an unseen agent acting with purpose is, as we have said, a suggestion quite valueless to science, because any conclusions it might lead to would not be scientific knowledge. If we assumed the existence of purpose, and even could conjecture dimly its nature, we still should have made no addition to those positive facts which are the only things that science is concerned to establish: it would be neither more nor less true than before that bishops move diagonally, pawns one square at a time, gravitating bodies at the rate of sixteen feet in the first second, and so on. It would be neither more nor less true than before that pawns actually were the first pieces to move in the game, that lifeless matter preceded the evolution of organisms. Above all, it would be neither more nor less true than before that the conclusions of science are the only conclusions that a rational man will accept. FOOTNOTES: [37] To say that my consciousness offers no such evidence is, if true, irrelevant. We are concerned with the consciousness of mankind generally. In astronomy the personal equation is allowed for; and in science generally the observations of one _savant_ are subject to confirmation or correction by others. XI. THE COMMON FAITH OF MANKIND