94. Purely experimental cognitions are confined to the sphere of experience; the idea of time extends to the whole real and possible order, it teaches us not only what _is_, but what _may_, and what _must_ be; its relations are of absolute necessity, and may be subjected to the strictest calculation; therefore it contains something more than the elements furnished by sensible or insensible experience. It is not otherwise possible to explain the necessity which it involves, or to pass beyond a collection of contingent facts to arrive at the possession of an element of science. 95. Let us observe, as we pass, that here is found another proof that the system of Condillac is neither true nor subsistent. His system has been found insufficient to explain any fundamental idea, and it does not explain the idea of time, any more than the rest, although it seems as though this idea must have the most intimate relations to the sensible order. 96. If the idea of time is not merely experimental, how explain the priority and necessity of time? CHAPTER XIII. KANT'S OPINION. 97. Kant uses the same theory to explain time that he used to explain space. Time, according to him, is nothing in itself, neither is it any thing in things; it is a subjective condition of intuition, a form of the internal sense, by means of which phenomena are presented to us as successive, just as space was the form by which they are presented as continuous. To speak frankly, it seems to me that this is saying nothing; it affirms a well-known fact, but does not explain it. Who does not know that what we perceive we perceive in succession--that we perceive even our own perceptions in succession? But what is succession? This is what he ought to have explained. 98. Kant says that time is only in us; but I should like to ask him, if succession is only in us. He pretends that we know nothing of the external world, but that we perceive certain appearances, or phenomena; but he does not deny that beyond the appearance there may be a reality. If this reality is possible, changes are possible in it; and change cannot be conceived without succession, nor succession without time. 99. According to Kant, the ideas of space and time are _à priori_, they cannot be empirical, or experimental; for in that case they could not be the basis of science; we could only affirm what we had experienced, and this only with respect to the cases in which we have experienced it. This is true, and I have demonstrated it in the last chapter; but, conceding this priority, it proves nothing in favor of Kant's system. The ideas of space and time, although _à priori_, may nevertheless correspond to something in reality, as follows from the theory by which I have explained them.