But even this _minimum_ of religious reflection which is required, according to M. Renan, for the perception of the unity of God, he grudges to the Semitic nations, and he is driven in the end (p. 73) to explain the Semitic Monotheism as the result of a religious instinct, analogous to the instinct which led each race to the formation of its own language. Here we miss the usual clearness and precision which distinguish most of M. Renan's works. It is always dangerous to transfer expressions from one branch of knowledge to another. The word 'instinct' has its legitimate application in natural history, where it is used of the unconscious acts of unconscious beings. We say that birds build their nests by instinct, that fishes swim by instinct, that cats catch mice by instinct; and, though no natural philosopher has yet explained what instinct is, yet we accept the term as a conventional expression for an unknown power working in the animal world. If we transfer this word to the unconscious acts of conscious beings, we must necessarily alter its definition. We may speak of an instinctive motion of the arm, but we only mean a motion which has become so habitual as to require no longer any special effort of the will. If, however, we transfer the word to the conscious thoughts of conscious beings, we strain the word beyond its natural capacities, we use it in order to avoid other terms which would commit us to the admission either of innate ideas or inspired truths. We use a word in order to avoid a definition. It may sound more scientific to speak of a monotheistic instinct rather than of the inborn image or the revealed truth of the One living God; but is instinct less mysterious than revelation? Can there be an instinct without an instigation or an instigator? And whose hand was it that instigated the Semitic mind to the worship of one God? Could the same hand have instigated the Aryan mind to the worship of many gods? Could the monotheistic instinct of the Semitic race, if an instinct, have been so frequently obscured, or the polytheistic instinct of the Aryan race, if an instinct, so completely annihilated, as to allow the Jews to worship on all the high places round Jerusalem, and the Greeks and Romans to become believers in Christ? Fishes never fly, and cats never catch frogs. These are the difficulties into which we are led; and they arise simply and solely from our using words for their sound rather than for their meaning. We begin by playing with words, but in the end the words will play with us.