We must distrust our intellectual vision: it is with chemical theories as with psychological systems. The mind, in order to account for phenomena, works with atoms, which it does not and can never see, as with the ME, which it does not perceive: it applies its categories to everything; that is, it distinguishes, individualizes, concretes, numbers, compares, things which, material or immaterial, are thoroughly identical and indistinguishable. Matter, as well as spirit, plays, as we view it, all sorts of parts; and, as there is nothing arbitrary in its metamorphoses, we build upon them these psychologic and atomic theories, true in so far as they faithfully represent, in terms agreed upon, the series of phenomena, but radically false as soon as they pretend to realize their abstractions and are accepted literally. 2. But what, then, is the source of this supposition that matter is impenetrable, which external observation does not justify and which is not true; and what is its meaning? Here appears the triumph of dualism. Matter is pronounced impenetrable, not, as the materialists and the vulgar fancy, by the testimony of the senses, but by the conscience. The ME, an incomprehensible nature, feeling itself free, distinct, and permanent, and meeting outside of itself another nature equally incomprehensible, but also distinct and permanent in spite of its metamorphoses, declares, on the strength of the sensations and ideas which this essence suggests to it, that the NOT-ME is extended and impenetrable. Impenetrability is a figurative term, an image by which thought, a division of the absolute, pictures to itself material reality, another division of the absolute; but this impenetrability, without which matter disappears, is, in the last analysis, only a spontaneous judgment of inward sensation, a metaphysical a priori, an unverified hypothesis of spirit. Thus, whether philosophy, after having overthrown theological dogmatism, spiritualizes matter or materializes thought, idealizes being or realizes ideas; or whether, identifying SUBSTANCE and CAUSE, it everywhere substitutes FORCE, phrases, all, which explain and signify nothing,--it always leads us back to this everlasting dualism, and, in summoning us to believe in ourselves, compels us to believe in God, if not in spirits. It is true that, making spirit a part of Nature, in distinction from the ancients, who separated it, philosophy has been led to this famous conclusion, which sums up nearly all the fruit of its researches: In man spirit KNOWS ITSELF, while everywhere else it seems NOT TO KNOW ITSELf--"That which is awake in man, which dreams in the animal, and sleeps in the stone," said a philosopher.