8. We pass by the physics of Descartes, which has only a subordinate philosophical interest, and notice next his views of anthropology. From this dualistic relation between mind and matter, there follows a dualistic relation between soul and body. If matter is essentially extension, and mind essentially thought, and if the two have nothing in common, then the union of soul and body can be conceived only as a mechanical one. The body is to be regarded as an artistic automaton, which God has made, as a statue or machine formed by God from the earth. Within this body the soul dwells, closely but not internally connected with it. The union of the two is only a powerful bringing of the two together, since each is not only an independent factor, but is essentially distinct from and even opposed to the other. The body by itself is a machine fully prepared, in which nothing is changed by the entrance of the thinking soul, except that through it certain motions are secured: the wheel-work of the machine remains as it was. It is only thought which distinguishes this machine from every other; hence, therefore, brutes which are not self-conscious nor thinking, must be ranked with all other machines. From this standpoint arose especially the question concerning the seat of the soul. If body and soul are independent substances, each essentially opposed to the other, they cannot interpenetrate each other, but can touch only at one point when they are powerfully brought together. This point where the soul has its seat, is, according to Descartes, not the whole brain but the pineal gland, a little kernel in the middle of the brain. The proof for this claim, that the pineal gland is the only place where the soul immediately exhibits its energy, is found in the circumstance that all other parts of the brain are twofold, which should not be in an organ where the soul has its seat, else objects would appear double. There is, therefore, no other place in the body where impressions can be so well united as in this gland. The pineal gland is, therefore, the chief seat of the soul, and the place where all our thoughts are formed.