It is the attempted unification of mind and body which brings us to the doctrine of monism. Under this general theory we find spiritual monism, materialism, panpsychism, epiphenom enon, mind-dust, etc. The most obvious means of reconciliation is that of resolving either one of the ultimate factors into the other. The metaphysical conception of materialism is the doctrine by which all substance whatsoever is conceived of as being reduced to matter, of which conscious mind is but a product. The chief objections urged against it are (1) that it makes our mental states, which of all knowl edge we know most immediately and directly, subordinate to our indirect and inferential knowledge of things; (2) that consciousness is a reality distinct from material phenomena, and therefore incapable of being analyzed into it; and (3) that no external world is possible apart from a perceiving subject. Spiritualism, on the other hand, escapes these objections by positing mind as the primordial substance, and further regarding material things as in themselves es sentially expressive of spirit. It encounters, however, certain difficulties in the concomi tance and juxtaposition of its elements for which, as yet, it has afforded no adequate solu tion.
According to Spinoza's doctrine of monism, both spirit and matter, or the mental and the material, are posited as real, self-existent reali ties, but not standing independent of each other. There is a common °substance," and in this, consciousness and extension, the funda mental attributes of external reality, find them selves connected. Hence the doctrine is neither
purely materialistic nor purely spiritualistic, but includes both these theories. The parallelism which physiological psychology demonstrates, then, in the two classes of phenomena, indicates not only their ultimate inseparability, but the fact that they are but different modes of mani festation of a common substance. Manifestly, then, this doctrine calls for no interaction theory and disposes of the troublesome ques tion of causal connection above referred to. There is no interaction, merely a parallelism. This parallelism, indeed, extends throughout all material objects, all of which thus assume a certain mental aspect also. It is at this point especially that monism parts company, in its speculation, from the teachings of non-specula tive psychology, according to which mind and consciousness are invariably coextensive.
Bain, A., 'Mind and Body' (1873; new ed., 1897) ; Binet, A., (L'ame et le corps' (Paris 1905) : Busse, L., 'Geist und Korper, Seele und Leib' (Leipzig 1903) ; James, W., 'Psychology) (New York 1890) ; Kuelpe, W., 'Outlines of Psychology' (London 1909) ; McDougall, W., 'Body and Mind' (London 1911); Strong, C. A., 'Why the Mind Has a Body' (New York 1903); Titchener, E. B., 'Textbook of Psychology' (New York 1910); Wundt, W., 'Human and Animal Psychology' (English translation, London 1901).