I. No one who possesses even a superficial acquaintance with physical science can read Comte's "Lecons" without becoming aware that he was at once singularly devoid of real knowledge on these subjects, and singularly unlucky. What is to be thought of the contemporary of Young and of Fresnel, who never misses an opportunity of casting scorn upon the hypothesis of an ether--the fundamental basis not only of the undulatory theory of light, but of so much else in modern physics--and whose contempt for the intellects of some of the strongest men of his generation was such, that he puts forward the mere existence of night as a refutation of the undulatory theory?[15] What a wonderful gauge of his own value as a scientific critic does he afford, by whom we are informed that phrenology is a great science, and psychology a chimaera; that Gall was one of the great men of his age, and that Cuvier was "brilliant but superficial"![16] How unlucky must one consider the bold speculator who, just before the dawn of modern histology--which is simply the application of the microscope to anatomy--reproves what he calls "the abuse of microscopic investigations," and "the exaggerated credit" attached to them; who, when the morphological uniformity of the tissues of the great majority of plants and animals was on the eve of being demonstrated, treated with ridicule those who attempt to refer all tissues to a "tissu generateur," formed by "le chimerique et inintelligible assemblage d'une sorte de monades organiques, qui seraient des lors les vrais elements primordiaux de tout corps vivant;"[17] and who finally tells us, that all the objections against a linear arrangement of the species of living beings are in their essence foolish, and that the order of the animal series is "necessarily linear,"[18] when the exact contrary is one of the best-established and the most important truths of zoology. Appeal to mathematicians, astronomers, physicists,[19] chemists, biologists, about the "Philosophie Positive," and they all, with one consent, begin to make protestation that, whatever M. Comte's other merits, he has shed no light upon the philosophy of their particular studies. To be just, however, it must be admitted that even M. Comte's most ardent disciples are content to be judiciously silent about his knowledge or appreciation of the sciences themselves, and prefer to base their master's claims to scientific authority upon his "law of the three states," and his "classification of the sciences." But here, also, I must join issue with them as completely as others--notably Mr. Herbert Spencer--have done before me. A critical examination of what M. Comte has to say about the "law of the three states" brings out nothing but a series of more or less contradictory statements of an imperfectly apprehended truth; and his "classification of the sciences," whether regarded historically or logically, is, in my judgment, absolutely worthless.