Though this general caution is at least equally applicable to the amateur excursions of the student whose mental training has been confined to some special group of experimental sciences into the field of metaphysical criticism, it would be a good rule for practice if every student of Metaphysics would consider it part of his duty to make himself something more than an amateur in at least one branch of empirical science; probably Psychology, from its historical connection with philosophical studies, presents unique advantages for this purpose. And conversely, no specialist in experimental science should venture on ultimate metaphysical construction without at least a respectable acquaintance with the principles of Logic, an acquaintance hardly to be gained by the perusal of Jevons’s _Elementary Lessons_ with a supplement of Mill. § 2. Cosmology, then, means the critical examination of the assumptions involved in the recognition of the physical as a distinct order of existence, and of the most general hypotheses employed by popular thought and scientific reflection respectively for the description of specially physical existence. It is clear that this very recognition of a distinction between the physical and other conceivable forms of existence implies a degree of reflective analysis more advanced than that embodied in the naïve pre-scientific view with which we started in our last two chapters. In the simple conception of the world of existence as consisting of the changing states of a plurality of interacting things, there was not as yet any ground for a distinction between the psychical and the purely physical. That there really exists a widespread type of thought for which this distinction has never arisen, is put beyond doubt by the study of the psychology of the child and the savage. Both, as we know, draw no hard-and-fast line between the animated and the inanimate, and the savage, in his attempts to account for the phenomena of life, does so habitually by supposing the physical organism to be tenanted by one or more lesser organisms of the same order of existence. The “soul” he ascribes to things is simply a smaller and consequently less readily perceptible body within the body.