Another comprehensive system was worked out by an Englishman, Herbert Spencer. Like Comte’s, it was based on science, and attempts to show how, starting with a nebular universe, the whole knowable world, psychical and social as well as physical, can be deduced. His Synthetic Philosophy perhaps did more than anything else to make the idea of evolution familiar in England. I must mention one other modern explanation of the world, that of Haeckel, the zoologist, professor at Jena, who may be called the prophet of evolution. His Creation of Man (1868) covered the same ground as Darwin’s Descent, had an enormous circulation, and was translated, I believe, into fourteen languages. His World-riddles (1899) enjoys the same popularity. He has taught, like Spencer, that the principle of evolution applies not only to the history of nature, but also to human civilization and human thought. He differs from Spencer and Comte in not assuming any unknowable reality behind natural phenomena. His adversaries commonly stigmatize his theory as materialism, but this is a mistake. Like Spinoza he recognizes matter and mind, body and thought, as [188] two inseparable sides of ultimate reality, which he calls God; in fact, he identifies his philosophy with that of Spinoza. And he logically proceeds to conceive material atoms as thinking. His idea of the physical world is based on the old mechanical conception of matter, which in recent years has been discredited. But Haeckel’s Monism, [1] as he called his doctrine, has lately been reshaped and in its new form promises to exercise wide influence on thoughtful people in Germany. I will return later to this Monistic movement. It had been a fundamental principle of Comte that human actions and human history are as strictly subject as nature is, to the law of causation. Two psychological works appeared in England in 1855 (Bain’s Senses and Intellect and Spencer’s Principles of Psychology), which taught that our volitions are completely determined, being the inevitable consequences of chains of causes and effects. But a far deeper impression was produced two years later by the first volume of Buckle’s History of Civilization in England (a work of much less permanent value), which attempted to apply this principle to history. Men act in consequence of motives; their motives are the results of preceding facts; so that “if we were acquainted with the whole of the antecedents [189] and with all the laws of their movements, we could with unerring certainty predict the whole of their immediate results.” Thus history is an unbroken chain of causes and effects. Chance is excluded; it is a mere name for the defects of our knowledge. Mysterious and providential interference is excluded. Buckle maintained God’s existence, but eliminated him from history; and his book dealt a resounding blow at the theory that human actions are not submitted to the law of universal causation.