Our author, having expounded this doctrine with much precision, proceeds to criticize it with equal sagacity. He points out what is illusory in this law of the three states; shows that it confuses metaphysic with scholasticism; and proves, finally, that, in aiming at merging mind in knowledge, and subordinating, as he says, the subjective to the objective, Positivism does not understand what it is speaking of, since all knowledge is ultimately referable to facts of consciousness--that is to say, to something subjective, which is in effect, as Descartes has pointed out, the only order of absolutely certain truths. Besides which, let positive science, or rather the positive philosophy, in the name of positive facts, proscribe metaphysic as it will, is it not evident that the fundamental conceptions of all science--number, atom, force, matter, cause, law--are metaphysical conceptions? Is it not evident that all science whatever is impossible without a certain number of principles or notions,--in a word, of intellectual laws, which even govern experience itself? As yet the positive school has not answered the learned demonstration of Kant on the necessity of the _à priori_ principle, or rather it has ignored it. It has made no addition to that old empiricism which the school of Leibnitz and of Kant had refuted. But since the Positivism of Auguste Comte, too little versed in metaphysical knowledge to discuss it authoritatively, there have arisen two important schools, the one of association, the other of evolution. The former has endeavoured to base experience on an experimental and positive law; the latter has generalized this law, and made of it a particular case of a more general law embracing the whole of Nature--namely, the law of evolution.