The place of the conception of the Ego in Kant's and Fichte's theory of knowledge is well known. Equally well known is Kant's treatment of the soul-reality or soul-substance in his examination of Rational Psychology. Whereas the (logical) unity of consciousness, or "synthetic unity of apperception," is assumed as a fundamental starting-point in explanation of our objective judgments, or of our knowledge of objective existence, its real (as opposed to its formal) foundation in a "substantial" soul is set aside as an illegitimate interpretation of, or inference from, the facts of inner experience. The belief in the separate unity and persistence of the soul, said Kant, is not a scientifically-warranted conclusion. Its true place is as an ineffaceable postulate of the faith which inspires human life and action. Herbart did not rest content with either of these--as he believed--dogmatic assumptions of his master. He did not fall in cheerfully with the idealism which seemed ready to dispense with a soul, or which justified its acceptance of empirical reality by referring to the fundamental unity of the function of judgment. With a strong bent towards fully-differentiated and individualised experience Herbart conjoined a conviction of the need of logical analysis to prevent us being carried away by the first-come and inadequate generalities. The Ego which, in its extremest abstraction, he found defined as the unity of subject and object, did not seem to him to offer the proper guarantees of reality: it was itself a problem, full of contradictions, waiting for solution. On the other hand, the real Ego, or self of concrete experience, is very much more than this logical abstract, and differs widely from individual to individual, and apparently from time to time even in the same individual. Our self, of which we talk so fluently, as one and the self-same--how far does it really possess the continuity and identity with which we credit it? Does it not rather seem to be an ideal which we gradually form and set before ourselves as the standard for measuring our attainments of the moment,--the perfect fulfilment of that oneness of being and purpose and knowledge which we never reach? Sometimes even it seems no better than a name which we move along the varying phenomena of our inner life, at one time identifying it with the power which has gained the victory in a moral struggle, at another with that which has been defeated(26), according as the attitude of the moment makes us throw now one, now another, aspect of mental activity in the foreground.