endeavoured to explain in the last chapters. But, if so, does it not follow that great as the importance of self-consciousness afterwards proves to be as a condition to the higher development of ideation, in itself, or in its first beginning, it does not betoken any very perceptible improvement upon those powers of pre-conceptual ideation which it immediately follows? In other words, there is thus shown to be even less reason to regard the advent of self-consciousness as marking a psychological difference of kind, than there would be so to regard the advent of those higher powers of conceptual ideation which subsequently—though as gradually—supervene between early childhood and youth. Yet no one has hitherto ventured to suggest that the intelligence of a child and the intelligence of a youth display a difference of kind. Or, otherwise stated, the psychological interval between my cebus and my child (when the former successfully investigated the mechanical principle of the screw by means of his highly developed receptual faculties, while the latter unsuccessfully attempted to solve a most simple topographical problem by means of her lowly developed conceptual faculties), was assuredly much less than that which afterwards separated the intelligence of my child from this level of its own previous self. Therefore, on merely psychological grounds, I conclude that there would be better—or _less bad_—reasons for alleging that there is an observable difference of kind between the lowest and the highest levels of conceptual ideation, than there is to allege that any such difference obtains between the lowest level of conceptual ideation and the highest level of receptual. “The greatest of all distinctions in biology,” when it first arises, is thus seen to lie in its _potentiality_ rather than in its _origin_. Self-consciousness is, indeed, the condition to an immeasurable change in the mind which presents it; but, in order to become so, it must be itself conditioned: it must itself undergo a long and gradual development under the guiding principles of a natural evolution. * * * * *