THE CREED OF A PHYSIOLOGIST.* Tuie little book consists of
four lectures delivered to senior students at Guy's Hospital, and forms, as the author says, an attempt to bring the great biological movement of the nine- teenth century into definite relation with the main stream of human thought. In the first lecture Dr. Haldane gives very fully and fairly the arguments for the mechanistic theory of life—which regards a living organism as no more than a com- plex system of physico-chemical mechanisms—and shows the weakness of the ordinary vitalist argument, which is only- an unproved hypothesis invented to cover ignorance. In the next lecture he examines more closely the mechanistic
• Mechanism, Life, and Personality : an Paamitudion of the Yeah n • tie Theory of Life and Mind. By I. S. Haldane, M.D., P.B.S. London:'.41 hlarrey, 0a, seta
• doctrine, and points out how, even on its own hypothesis, it provides no answer to the difficulties. For example, there is no warrant for identifying, as the mechanists do, the " stimulus " and " response "of physiology with physical cause and effect, and modern progress in physiology, so far from verifying the mechanistic theory, tends to show that physico- chemical explanations of physiological processes are wholly inadequate to the facts. Thus, "the mechanistic theory of heredity is not merely unproven, it ie impossible. It involves such absurdities that no intelligent person who has thoroughly realized its meaning and implications can continue to hold it." Dr. Haldane then gives us a brief survey of the history of mechanistic theory, and explains how in biology we use a fundamental conception different from those of the physical sciences—the conception of a living organism. He illustrates its use from the actual course of physiological investigation, and shows that the ideal of biology is not to reduce the organic to the inorganic, like the mechanists, but the inorganic to the organic. Even physicists and chemists to-day are groping after biological ideas. The last lecture deals with the characteristics of the higher organism, consciousness and personality. A person is not related merely externally to his surroundings, for the surroundings are teleologically determined in relation to his organic life. A person is more than a mere organism, as an organism is more than mere matter ; the relation between the three is that of different degrees of nearness to reality. Personality or spirit is the central and concrete reality of the universe
The astronomer or the physiologist seems, at first sight, to be presenting to us a gigantic and absolutely inhuman universe, in which man and human activity is but a tiny speck. Most people simply shut their eyes to this picture in its entirety. Few have the courage to face it. But it was faced by the eighteenth- century philosophers. Hume pointed out that there is one all- important element in the picture which most people leave out of account, and this is that the picture is only a picture.. . . Kant and his successors taught us to see in part how the picture is painted, and to realise that it is only one expression of human per- sonality—the personality typified in the lonely and heroin figure of Copernicus. Those who have read Heine's Deutschland will remember his account, scintillating with the flashes of his wonder- ful literary genius, of Immanuel Kant, whom he represented as the Robespierre of an intellectual revolution far more wide-reaching in its effects than the French Revolution. The victim of this intellectual revolution was pictured as no mere earthly king, but the God of Hebrew and Christian tradition. ' I can hear the bell. Kneel down. They are bringing the sacraments to a dying God.' Heine was right in his estimate of the importance of Kant's work. But it was the god of materialism, and not of Christianity, that was dying."
Dr. Haldane's little book is written with exceptional clear- ness and distinction. The illustrations from his own branch of science are skilfully chosen, and the whole argument is a model of what philosophical argument should be. The book deserves to he read and re-read by all who are interested in the modern relations of philosophy and the natural sciences.
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