an act of integrating. That is to say, there must be a continuous integration of states of consciousness. These are the two antagonist processes by which consciousness subsists-the centrifugal and centripetal actions by which its balance is maintained. That there may be the material for thought, consciousness must every moment have its state differentiated. And for the new state hence resulting to become a thought, it must be integrated with before-experienced states. This perpetual alternation is the characteristic of all consciousness from the very lowest to the very highest. It is distinctly typified in that oscillation. between two states, constituting the simplest conceivable. form of consciousness; and it is illustrated in the most complex thinkings of the most cultivated man. This law is displayed also in the general progress of thought. These small differentiations and integrations that go on from moment to moment, result in those great differentiations and integrations which constituto mental development. Every case in which an advancing intelligence distinguishes between objects, or phenomena, or laws, that were previously confounded together, implies a differentiation of states of consciousness. And every case in which such advancing intelligence recognizes as of the same essential nature, objects, or phenomena, or laws, that were previously thought distinct, implies an integration of states of consciousness. Under its most general aspect, therefore, all mental action whatever is definable as the continuous differentiation and integration of states of consciousness. §383. The only fact of importance remaining to be pointed out, is the harmony which subsists between this final result and that reached by a kindred science. The widest truth disclosed by the inquiries of biologists is parallel to the one at which we have just arrived. As there are two antagonist processes by which cou sciousness is maintained, so there are two antagonist processes by which bodily life is maintained. By the actions it is exposed to every tissue is being differentiated; and every tissue is integrating the materials supplied by the blood. No function can be performed without the differentiation of the tissue performing it; and no tissue is enabled to perform its function save by the integration of nutriment. In the balance of these two actions the organic life is maintained. By each new integration an organ is fitted for being again differentiated; while each new differentiation enables the organ again to integrate. as with the psychical life, so with the physical-the stopping of either process is the stopping of both. And Moreover the parallel equally holds under the second aspect. Commencing as a uniform mass of matter, every organism is evolved by the differentiation and integration of parts. So, too, on contemplating the phenomena of organization at large as exhibited throughout creation, we find that the integration of elements which perform the same function, goes on pari passu with the differentiation of elements which perform diverse functions. That advance from homogeneity to heterogeneity, in which all organization consists, is wholly effected by this duplex action. Thus, in two senses, there is a continuous differentiation and integration throughout the body; as, in two senses, there is a continuous differentiation and integration throughout the mind. When we remember that the laws of structure and function must necessarily harmonize; and that the structure and function of the nervous system must conform to the laws of structure and function in general; we shall see that the parallelism here roughly indicated is such as might be expected. We shall see that the ultimate generalizations of Psychology and Physiology must be, as they here appear, different sides of the same primordial truth: both are expressions of the same fundamental process of Life. CHAPTER I. THE FINAL QUESTION § 384. When at the outset "The scope of Psychology was considered, it was pointed out (§ 53) that "that which distinguishes Psychology from the sciences on which it rests, is, that each of its propositions takes account both of the connected internal phenomena and of the connected external phenomena to which they refer. * * Suppose that * A and B are two related manifestations in the environment -say, the colour and taste of a fruit; then, so long as we contemplate their relation by itself, or as associated with other external phenomena, we are occupied with a portion of physical science. Now suppose that a and b are the sensations produced in the organism by this peculiar light which the fruit reflects, and by the chemical action of its juice on the palate; then * * * we pass into the domain of Psychology the moment we inquire how there comes to exist within the organism a relation between a and b that in some way or other corresponds to the relation between A and B." The problem of Psychology as thus posited, presents different aspects according as one or other of the interdependencies among these relations is made the dominant topic. Bearing in mind that the law of the relation A B, is the problem of Objective Science, which takes for granted that a b answers to it, we have to cbserve that the problem of Subjective Science is divisible into two problems, |