On the other hand, if the question is of the hypothetical origin of mind, we are at once brought face to face with an ultimate metaphysical problem which the new psychology impatiently ignores, which Spencer grudgingly acknowledges, but which Wundt and Kantians like Riehl find confronting them at every stage of their analysis. Conscious mind cannot conceive of its own origin, and therefore all psychological theories of development must postulate in some form the elements of consciousness and will. Nothing that I could add to the dialectics of this question would influence those who feel no difficulty here. They require a long course of Kantian criticism or its equivalent. At any rate it is not fair polemic to class a thinker as unscientific merely because he recognises this difficulty and gives it expression in his psychology, instead of contemptuously relegating it to metaphysics. After thus laying the foundations in the doctrine of apperception for the psychology both of cognition and of the will, Wundt proceeds to restate the associationist analysis of Mill and Spencer in a more elaborate terminology but in substantial agreement with Spencer till he reaches the “concept,” when the introduction of apperception gives rise to a seeming difference. Spencer distinguishes simultaneous from successive association as carefully as Wundt. What Wundt, after Herbart calls “complications,” namely the joint reference to one object of a number of disparate presentations of sense, is clearly described by Spencer (“Principles of Psychology,” §§ 315-355); and Wundt’s “assimilations” do not differ appreciably from Spencer’s “still less conscious” processes of “organic classification” (“Principles of Psychology,” § 320). Into the metaphysics of the ultimate relations of contiguity and similarity as laws of association I cannot enter here. Similarity will always be recognised as ultimate by those who, like Spencer, approach the problem first from the psychical side, while a purely materialistic treatment in terms of nervous currents, such as we find in James, will endeavor to do away altogether with similarity, which simply cannot be expressed in terms of nerve-structure without reasoning in a circle. Wundt retains similarity but endeavors to coördinate it with contiguity. The problem is really identical with the final question of the relations of “mind” and “body,” and cannot be profitably discussed apart from that question.