There was little trouble for Descartes in conceiving the movements of inanimate bodies, plants, and all the lower animals as purely mechanical and automatic, with their first cause in God. From his own investigations he felt obliged to regard many of the human functions as automatic also. But his ethical and theological interests compelled him to think of man as exalted above the rest of creation. Theology has always been in a sense aristocratic, and has drawn a line between man and other things. Man alone has a soul in his body. The soul of man is immortal and free, and must therefore have control over the body; nevertheless the soul of man must be conscious of the impressions that come through the body. Here the science of the Renaissance and the scholasticism of the Middle Ages refuse to be reconciled in the philosophy of Descartes. When it became a question between Descartes’ scientific theory of matter operating itself mechanically and the church doctrine of a spiritual will operating the matter of the human body, the scientific theory had to yield. How does Descartes yield gracefully to the theological requirements and bring together the two unlike worlds of matter and mind in the human personality? Descartes’ explanation of the relation of human mind and body reminds us of the mythical explanations of Paracelsus. The soul is united to all parts of the body, but its point of contact with the body is the pineal gland, and this contact is made possible through the animal spirits (_spiritus animales_) or the fire atoms in the blood, a revived Greek conception. The pineal gland is a ganglion in the centre of the brain, which biologists tell us is a defunct eye, but which Descartes conceived to be the seat of the soul. Descartes maintained that the animal spirits, having been distilled by the heart, ascend by mechanical laws from the heart to the brain, and then descend to the nerves and muscles. When they pass through the pineal gland, they come in contact with the soul. The soul exercises influence on the body by slightly moving the gland and diverting the animal spirits. In this way the emotions and sensations are to be explained. The movement of the pineal gland by the animal spirits causes sensations in the soul; the movement of the gland by the soul changes the movement of the animal spirits, and is an exhibition of free action. But this does not add to or subtract from the energy. It merely changes the direction of energy.