In order to reject the postulate admitted by philosophers before him, he appeals at the same time to arguments founded on facts and demonstration; but we must notice that, in his doctrine, these two orders of arguments logically reduce themselves to one another. Indeed he says, up to the present time no philosophy which commands acceptance by all minds has been established. Idealisms, materialisms, pantheisms from all sources and in every shape have never done more than ruin the doctrines opposed to them, without becoming finally established themselves. Those systems claimed to give a rational knowledge of that which by nature is beyond the reach of science. They prided themselves upon explaining the essence, the cause, the end and the order of the phenomena of the universe. Thus they could only build up temporary conceptions which were undoubtedly indispensable at the time but which were doomed to die. Metaphysics is never anything but a rationalised theology which is weakened by this very fact, and deprived of what constituted its strength during the period when it was an object of belief. But in the name of what principle can Comte discern what is and what is not “beyond the reach of science?” In order to justify a distinction of this kind should he not before everything begin by a criticism of the human mind, that is to say by a theory of knowledge similar to that proposed by Kant in his “Criticism of Pure Reason”? M. Renouvier endeavours to show that, through the absence of this preliminary criticism, with which Comte dispensed, his philosophy remains superficial. Mr. Max Muller expressly says that there is no need to take into account a philosophical doctrine which proceeds as if the “Criticism of Pure Reason” had not been written. On the whole the objection reduces itself to reproaching Comte with not having attempted to do what he considered to be impracticable: namely, not to have determined the intellectual laws by the analysis of the mind reflecting upon itself. But, it is said, by what right does he affirm that this is impossible? Because, like all the others, these laws can only be discovered by means of the observation of facts, and because the only method which is suitable for the discovery of intellectual facts is the sociological method: the nature of these facts being such that, especially from the dynamic point of view, they can only be grasped in the evolution of humanity. The theory of knowledge demanded by M. Renouvier and Mr. Max Muller is not wanted in positive philosophy. It is not seen in this philosophy, because it is not presented in its traditional form. It is there none the less; but, instead of consisting in an analysis _a priori_ of thought, as a preliminary to philosophy, it is not separated from the philosophy itself. It is one of the many aspects of sociology.