However, we must consider carefully. Having thoroughly reflected, we shall ask if this fortress be real, or if, on the contrary, it be not, perhaps, a representation without object, a pure phantom, like those sunken cities whose bells still ring for great festivals, but are heard only by those who believe in their mysterious life. This doubt will lead us to re-examine the reasoning of Berkeley and of Kant, and see if it be well constructed. Does it start from the senses to reach the mind? Or may it not, perchance, be one of those mental conceptions which fall back upon the senses like an avalanche, freezing and smothering them? How have the senses been formed? Such is the question. Has there always been an opposition between the ego and the non-ego? There is nothing in the intelligence that has not first been in the senses. By intelligence, we must in this philosophic dictum, due to Locke, understand the psychologic consciousness. Let us leave aside the consciousness, which can only serve to complicate the problem. Consciousness is a phenomenon of secondary order and of an entirely sentimental utility, if it be restricted to man; commonplace and of pure reflex, if extended to all sensible matter. Let us consider this matter in perhaps its humblest manifestations, taking account only of the actions and reactions, exactly as we might observe the influence of heat, of light, or of cold on milk, wine or water. In living matter there will, however, be something more--the decomposition will be compensated by assimilation, and if the assimilation be abundant, there will be generation. Other forms, resembling the first, will detach themselves from the matrix form. This represents life essentially, a living being, a being limited in duration by the very fact of its growth, which constitutes an effort and a loss. Let us consider a being whose senses are not differentiated, and let us see how it gets on with the rest of the world, how it knows it.