Science and miracle have been fighting out their battle during the last fifty years along the whole line, and science has been at every point victorious. Miracle, in the sense in which our fathers believed in it, has been not only repulsed, but annihilated so completely, that really little remains but to bury the dead. The result of these discoveries has been to make a greater change in the spiritual environment of a single generation than would be made in their physical environment if the glacial period suddenly returned and buried Northern Europe under polar ice. The change is certainly greater in the last fifty years than it had been in the previous five hundred, and in many respects greater than in the previous five thousand. It may be sufficient to glance shortly at the equally great corresponding changes which this period has witnessed in the practical conditions of life and of society. If astronomy and geology have extended the dominion of the mind over space and time, steamers, railways, and the electric telegraph have gained the mastery over them for practical purposes. Commerce and emigration have assumed international proportions, and India, Australia, and America are nearer to us, and connected with us by closer ties, than Scotland was to England in my schoolboy days. Education and a cheap press have even in a greater degree revolutionised society, and knowledge, reaching the masses, has carried with it power, so that democracy and free-thought are, whether for good or evil, everywhere in the ascendant, and old privileges and traditions are everywhere decaying. With such a great change of environment it is evident that many of the old creeds, institutions, and other organisms, adapted to old conditions, must have become as obsolete as a schoolboy’s jacket would be as the comfortable habiliment of a grown-up man. But as a lobster which has cast its shell does not feel at ease until it has grown a new one, so thinking men of the present day are driven to devise, to a great extent each for themselves, some larger theory which may serve them as a ‘working hypothesis’ with which to go through life, and bring the ineradicable aspirations and emotions of their nature into some tolerable harmony with existing facts. To me, as one of those thinking units, this theory, of what for want of a better name I call ‘Zoroastrianism,’ has approved itself as a good working theory, which reconciles more intellectual and moral difficulties, and affords a better guide in conduct and practical life than any other; and, in a word, enables me to reduce my own individual Chaos into some sort of an intelligible and ordered Cosmos. I feel moved, therefore, to preach through the press my little sermon upon it, for the benefit of those whom it may concern, feeling assured that the process of evolution, by which The old order changes, giving place to new,