persistently declining to accept anything without sufficient evidence. In ordinary life, says the man of science, we do not swallow any statement that anybody chooses to make--we ask for some evidence; and if science waxes every day, and religion wanes, it is merely because science has made it the rule of her being never to believe anything without sufficient evidence, and religion has not. Naturally, then, we wish to know what is "sufficient evidence" in the eyes of science, since everything, we are told, depends on that. The reply is brief: whatever is based on the Uniformity of Nature has sufficient evidence. If we are inclined to be puzzled by the "Uniformity of Nature," we are soon reassured; it is literally the most ordinary thing in the world, there is no difficulty about it. Man is born into a world in which changes are unceasingly taking place. Some things change even as the clouds shift--every second, and in a way patent to all beholders. Others change imperceptibly and with great slowness, as _e.g._ the level of the dry land or the shape of the coast-line. But all things change, _πάντα ῥεῖ_. Nothing abideth long in one stay. It is these changes which bring all things good to man, and also all things ill. If, then, man is to survive, he must learn to evade the latter changes, which threaten to crush him, and he must be there in time to profit by the former. Such was the problem presented to primitive man, and such it still is for every one of us to-day: the successful man is the one who is beforehand with the world, and, if he is beforehand it is because he has learned to read the signs of the times and the seasons. In a word, he has learned to recognise that changes are not always mere chances, that some changes are uniformly preceded by certain others, and may consequently be foreseen. In the beginning the changes that man can forecast are few indeed: his prevision is no greater than the brute's. The child does not foresee that fire will burn; he learns by experience. And whatever man can forecast, he has learned it all by experience. It is a slow way of learning, it has taken man thousands upon thousands of years to learn what he knows now; still he has learned to know the causes of countless things, to control the causes and to anticipate the effects of many. But more important, more valuable than all his experience and all his knowledge of what produces what, of what uniformly precedes or follows what, is the final and comprehensive truth which at last he reaches, that nothing happens arbitrarily, that everything in nature is uniform. That, the Uniformity of Nature, is the great truth in which all others are summed up: to its establishment have gone the labours of all past generations of mankind, to its support the whole experience of the race contributes. It is the truth of truths, the test of truth: whatsoever is established on it shall not be shaken, whatever contravenes it shall not endure.