There is in the philosophy of sensation what is true and what is false. The false is the pretension of explaining all human knowledge by the acquisitions of the senses; this pretension is the system itself; we reject it, and the system with it. The true is that sensibility, considered in its external and visible organs, and in its internal organs, the invisible seats of the vital functions, is the indispensable condition of the development of all our faculties, not only of the faculties that evidently pertain to sensibility, but of those that seem to be most remote from it. This true side of sensualism we have everywhere recognized and elucidated in metaphysics, aesthetics, ethics, and theodicea. For us, theodicea, ethics, aesthetics, metaphysics, rest on psychology, and the first principle of our psychology is that the condition of all exercise of mind and soul is an impression made on our organs, and a movement of the vital functions. Man is not a pure spirit; he has a body which is for the spirit sometimes an obstacle, sometimes a means, always an inseparable companion. The senses are not, as Plato and Malebranche have too often said, a prison for the soul, but much rather windows looking out upon nature, through which the soul communicates with the universe. There is an entire part of Locke's polemic against the theories of innate ideas that is to our eyes perfectly true. We are the first to invoke experience in philosophy. Experience saves philosophy from hypothesis, from abstraction, from the exclusively deductive method, that is to say, from the geometrical method. It is on account of having abandoned the solid ground of experience, that Spinoza, attaching himself to certain sides of Cartesianism,[267] and closing his eyes to all the others, forgetting its method, its essential character, and its most certain principles, reared a hypothetical system, or made from an arbitrary definition spring with the last degree of rigor a whole series of deductions, which have nothing to do with reality. It is also on account of having exchanged experience for a systematic analysis, that Condillac, an unfaithful disciple of Locke, undertook to draw from a single fact, and from an ill-observed fact, all knowledge, by the aid of a series of verbal transformations, whose last result is a nominalism, like that of the later scholastics. Experience does not contain all science, but it furnishes the conditions of all science. Space is nothing for us without visible and tangible bodies that occupy it, time is nothing without the succession of events, cause without its effects, substance without its modes, law without the phenomena that it rules.[268] Reason would reveal to us no universal and necessary truth, if consciousness and the senses did not suggest to us particular and contingent notions. In aesthetics, while severely distinguishing between the beautiful and the agreeable, we have shown that the agreeable is the