This effort has led to the theory of two substances, the soul and the body, which are represented as being as thoroughly separated as possible. The soul has not its origin in the body, and it derives none of its properties from its fellow; it is a substance created in complete independence relatively to the body; the soul, in its essence, has nothing in common with matter. The essence of the soul, said Descartes, is thought; the essence of the body is extent. It follows from this that the soul, in its determinations and actions, is liberated from the laws and necessities of the corporeal nature; it is a free power, a power of indetermination, capable of choice, capable of introducing new, unforeseen, and unforeseeable actions, and on this point opposes itself to corporeal phenomena, which are all subject to a determinism so rigorous that any event could be foreseen if its antecedents were known. Another consequence of spiritualism is the admission of the immortality of the soul, which, being widely distinct from the body, is not affected by its dissolution; it is, on the contrary, liberated, since death cuts the link which binds them together. But there is a link, and the explanation of this link brings with it the ruin of the whole system. One is forced to admit that this principle of the separation of body and soul is liable, in fact, to many exceptions. Even if they are two isolated powers, the necessities of life oblige them to enter continually into communication with each other. In the case of perceptions, it is the body which acts on the soul and imparts sensations to it; in movements, it is the soul, on the contrary, which acts on the body, to make it execute its desires and its will. Spiritualists must acknowledge that they are at some trouble to explain this traffic between the two substances; for, with their respect for the principle of heterogeneity mentioned above, they do not manage to conceive how that contact of the physical and the mental can be made which is constantly necessary in the life of relation. By what means, have they long asked themselves, can that which is only extent act on that which is only thought? How can we represent to ourselves this _local_ union of matter with an immaterial principle, which, by its essence, does not exist in space? The two substances have been so completely separated, to insure the liberty of the soul and its superiority over the body, that it has become impossible to bring them together. The scission has been too complete. They cannot be sewn together again. Such are the principal objections raised against spiritualism. These objections are derived from points of view which are not ours, and we have therefore no need to estimate their value.