It might have been thought that the principle of Development had exhausted its powers, and achieved its highest triumphs, when it had been applied successively to account, first, for the creation of planets and astral systems, and, secondly, for the production of vegetable and animal life; and that little could remain for it to do after it had succeeded in tracing the genealogy of MAN back, in a direct line through many generations, to the nebulous matter or luminous Fire-Mist which was diffused at the beginning of time throughout the Universe. But, on a more careful study of its last and highest product,--MAN, with his intellectual and moral nature, his religious beliefs, his social history, and his immortal hopes,--it seemed as if there were still some phenomena which remained to be accounted for, some facts of palpable reality and great magnitude which had not yet been adequately explained. The mental faculties and their operations, the moral laws that are universally recognized and appealed to, the social institutions which have been established, the religious beliefs and feelings which have generally prevailed, and the rites of worship which have been observed in all ages and climes, were so widely different from the phenomena of mere vegetable or animal life, that they seemed to demand a distinct account of their origin; and it might not be apparent, at first sight, how they could be reduced under the same all-pervading law by which the planets were formed, so as to exclude all idea of Divine supernatural interposition. This Herculean task was fearlessly undertaken, however, by M. AUGUSTE COMTE, and it has been elaborated with singular ability in his ponderous work, the "Cours de Philosophie Positive." M. Comte's Course of Positive Philosophy began to be delivered at Paris in the winter of 1829-30, and was completed in its published form in 1842-43. It comprehends a general outline of all the branches of Inductive Science, and of the relations which they bear to each other; and they are expounded in a style singularly copious, clear, and forcible. He has acquired, in consequence, a high reputation as a philosophical thinker, and has already found, in our own country, some able allies, and not a few enthusiastic admirers. The "System of Logic," by John Stuart Mill, and "The Biographical History of Philosophy," by G. H. Lewes, are avowedly indebted to his speculations for some of their most characteristic contents; while the outline of his theory has been presented to the more popular class of readers in England through the columns of "The Leader," and in Scotland through those of "The Glasgow Mechanics' Journal."