another opinion appear not to have thought enough upon the consequences of the difference which there is between necessary or eternal truths and the truths of experience, as I have already observed, and as all our discussion shows. The original proof of the necessary truths comes from the understanding alone, and the other truths come from experience or from the observation of the senses. Our mind is capable of knowing both; but it is the source of the former, and, whatever number of particular experiences we may have of a universal truth, we could not be assured of it forever by induction without knowing its necessity through the reason. Ph. But is it not true that if the words, to be in the understanding, involve something positive, they signify to be perceived and comprehended by the understanding? Th. They signify to us wholly another thing. It is enough that what is in the understanding can be found there, and that the sources or original proofs of the truths which are in question are only in the understanding; the senses can hint at, justify, and confirm these truths, but cannot demonstrate their infallible and perpetual certainty. . Ph. Nevertheless, all those who will take the trouble to reflect with a little attention upon the operations of the understanding will find that this consent, which the mind gives without difficulty to certain truths, depends upon the faculty of the human mind. Th. Very well. But it is this particular relation of the human mind to these truths which renders the exercise of the faculty easy and natural in respect to them, and which causes them to be called innate. It is not, then, a naked faculty ,which consists in the mere possibility of understanding them; it is a disposition, an aptitude, a preformation, which determines our soul and which makes it possible for them to be derived from it. Just as there is the difference between the figures G which are given to the stone or the marble indifferently, and between those which its veins already indicate, or are disposed to indicate, if the workman profits by them. Ph. But is it not true that the truths are subsequent to the ideas of which they are born? Now, the ideas come from the senses. Th. The intellectual ideas, which are the source of necessary truths, do not come from the senses; and you admit that there are some ideas which are due to the reflection of the mind upon itself. For the rest, it is true that the express knowledge of truths is subsequent {tempore vel natura) to the express knowledge of ideas; as the nature