This objection, be it observed, _assumes_ that there are so many globes similar to the earth, and like her revolving,—some accompanied as she is, by satellites,—on their axis, and that therefore it is reasonable to suppose the destination and office of all, the same;—that there are so many stars, each, like our sun, a source of light, probably also of heat; and that it is consequently reasonable to suppose their light and heat, like his, imparted, as from so many centres of systems, to uphold life;—and that all this affords strong ground for believing all such planets, as well those of our own as of other systems, inhabited like our planet. But the Essayist again directs the eye of the questioner to the state of our own planet, as demonstrated by Geology, in order to show the precariousness, if not futility, of supposing such an analogy to exist. It would lead us to a palpably false conclusion—viz., that during all the vast successive periods of the Earth’s history, that Earth was occupied with life of the same order—nay, even, that since the Earth is now the seat of an intelligent population, it must have been so in all its former conditions. For it was then able, and adapted, to support animal life, and that of creatures pretty closely resembling man[31] in physical structure. Nevertheless, if evidence go for anything, the Earth did not do so! “Even,” says Dr Whewell, “those geologists who have dwelt most on the discovery of fossil monkeys, and other animals nearest to man, have not dreamed that there existed, before him, a race of rational, intelligent, and progressive creatures.”[32] Here, however, he is mistaken, as we shall presently see Sir David Brewster revelling in such a dream. As, then, the notion that one period of time in the Earth’s history must resemble another in the character of its population, because it resembles it in physical conditions, is negatived by the history of the Earth itself; so the notion that one part _of the universe_ must resemble another in its population, because it has a resemblance in physical conditions, is negatived, as a law of creation. Analogy really affords no support to such a notion. IV. Nay, continues Dr Whewell,[33] we may go further: instead of the analogy of creation pointing to such entire resemblance of similar parts, it points in the opposite direction: it is not entire resemblance, but universal difference, that we discover: not the repetition of exactly similar cases, but a series of cases perpetually dissimilar, presents itself: not constancy, but change—perhaps advance; not one permanent and pervading scheme, but preparation, and completion of successive schemes:—not uniformity, and a fixed type of existences, but progression and a climax.