§ 1. Relativity.—"By the principle of relativity it is denied that any psychic factor, or complex psychosis,* can exist without having its own definite quality, quantity, tone of feeling, value in combination, and influence upon simultaneous or successive factors and psychoses, determined by the relation in which it stands to other factors and psychoses in the entire mental life. Or—stated positively—every individual element, or state, or form of mental life is what it is only as relative to other elements, states, and forms of the same mental life."+More briefly we may say: Mental development depends on modes of consciousness being determined by their psychological relations and subject to modification accordingly. This statement, though sufficiently comprehensive, is proportionately vague. The vagueness lies mainly in the phrase "psychological relations." What is the nature of the psychological relations through which modes of consciousness are enabled to interact ? To understand this we must consider the unity and continuity of consciousness. This topic falls under two heads, (1) general unity and continuity, and (2) the special unity and continuity constituted by conation.

* Psychos is = total state of consciousness as existing at any one moment. +Ladd, Psychology, Descriptive and Explanatory, pp. GG12.

§ 2. General Unity and Continuity.—The partial constituents of our conscious life are, as Dr. Ward puts it, not disjoined from one another by something which is disparate in nature from consciousness. They are not separated "as one island is separated from another by the intervening sea, or one note in a melody from the next by an interval of silence."* The unity and continuity of consciousness conceived in this most abstract and general form enables us to recognise what we may call relations of immediate contiguity. Whatever components of any given moment enter into the composition of a single state of consciousness are immediately contiguous. Similarly, successive states are in immediate contiguity if and so far as the termination of one coincides with the commencement of another. "At any given moment," says Dr. Ward, we have "a field of consciousness,' psychologically one and continuous; at the next, we have not an entirely new field but a partial change within this field."In as much as the emergence of the new is a modification of the old, they are continuous and so far psychologically contiguous. We have not merely A and then B, but also the passage of A into B; and this passage as such is a modification of consciousness. The transition is itself an experience. It is the more obviously so the more abrupt it is. The interruption, being a felt interruption, itself constitutes a relation between the two states, however unlike they may be. Take for instance an illustration given by Dr. Ward in another context—the "passing from the scent of a rose to the sound of a gong or a sting from a bee."+Professor Ladd well remarks, that in "the case of so abrupt a transition in the content and feeling-tone of two successive mental states, the law of relativity would not be violated, but the more amply illustrated. The amount of our absorption in the scent of the rose would influence the redistribution of attention to the sound of the gong, and even to the sting of the bee; the degree of pain which the succeeding sensations of sounds or smarting gave would be enhanced by the preceding pleasure; the control of the motor results of [movements prompted by] the new sensation would bo determined by the perceptions, etc., into which the sensation abruptly broke; and so on, and so on."*

*Article "Psychology," in the Encyclopaedia Britannica, 9th edition, part xx., p. 45.

+Ibid.                                    + Op. cit., p. 50.

Thus there are relations arising out of the unity of a single state of consciousness as it exists at any moment, and there are also relations arising out of the transition from one state to another. These relations involve immediate contiguity in time; either in the way of simultaneous existence or of continuous succession. But there is another kind of psychical connexion independent of direct proximity in time, and arising out of a more special and intimate continuity than that which is characteristic of the flow of consciousness in general.

* Psychology, Descriptive and Explanatory, p. 663.