and externalization, or the expansion and growth of mind, it would seem almost as if the existence of mind were assumed. At any rate, its existence is not absolutely denied or made identical with matter.
There are scientists who think of mind as they think of matter, and therefore study its operations as if it were the product of physical forces alone. They are not surprised at the conclusions of Cabanis that thought is a product of the brain as organized matter. These conclusions seem to them the logical outcome of Locke's theory of knowledge and of the philosophy taught by the Frenchmen Abbé Condillac and Helvetius. To them there seems to be no good reason why phrenology should not be able to locate the different powers of the brain, as Gall and Spurzheim tried to do at the beginning of the last century, even if no attempt were made to account for the existence of that something called mind which makes use of the brain.
However close we admit the relations to be between mind and matter, however fully we may believe in the influence of the physical upon the mental machine in man, it is well-nigh impossible to escape the conviction that mind and matter are diverse in their nature, that even if mind makes use of matter in its operations and is aided by it so that mind and matter may properly be studied together as a new science, they are not thereby made one and the same thing. There are many who still look upon physiology and psychology as different sciences, and while recognizing their close relationship and welcoming the results of studies and experiments in the border land between the two, they still feel as if there were a science of mind which demands other experiments and studies than those which physiology is able to furnish. Nevertheless, it is certain that in all future studies of mental philosophy the physical nature of man will be taken into account.
From this brief review of theories concerning the universe, its origin and meaning, each of which has been prominent in its turn, each of which indicates a different point of view on the part of its defenders, and each of which has in it a great deal of truth, it is clear that no one of them can now be accepted as completely satisfactory or as covering all the problems which meet us in trying to explain the universe. Taken together, they disclose and give a reason for many of the processes of nature, but they do not explain them all. Indeed, with every new discovery new vistas open, new questions arise, new difficulties are to be met. We may, therefore, content ourselves by accepting that as true which is proved to be true by all the theories. The fact of gravitation is undeniable, even if the astronomical theory is no longer received as adequate. Although no one has ever yet seen an atom, sound reasoning seems to require us to admit the existence of atoms and justifies us in appealing to mathematics to prescribe the laws of an atomic world. Nor can we deny the evidences of universal motion, or that the kinetic theory has a good basis upon which to stand. Equally evident is it