How we come in general to assume that there is something exterior, and that changes perceived by us only in our organism can have causes which are not in the organism itself, is a question over which metaphysics has cudgelled its brain for centuries. So little has it found an answer, that, in order to put an end to this difficulty anyhow, it has simply denied the very question, and jumped to the conclusion that the ‘I’ has actually no knowledge of a ‘not-I,’ of an external world, and cannot have it because there is no external world at all, that what we so call is a creation of our mind, and exists only in our thought as a presentation, but not outside our ‘I’ as a reality. It is a fact characteristic of the soporific action exercised by the sound of a word on the human mind that this wholly senseless cackle, glib, well arranged and formed into the philosophical system of idealism, should have thoroughly satisfied for nearly eight generations the greater number of professional metaphysicians, from Berkeley to Fichte, Schelling and Hegel. These wise men repeated, in a tone of conviction, the doctrine of the non-existence of the ‘not-I,’ and it did not trouble them that they themselves contradicted constantly, in all their actions, their own fustian; that they devoted themselves from their birth to their death to an uninterrupted series of absolutely absurd actions, if there were no objective external world; that therefore they themselves recognised their system to be but wind and shadow, a childish game with words devoid of sense. And the most logical among these grave drivellers, Bishop Berkeley, did not even observe that after all he had not obtained, even at the price of the total abdication of common sense, the answer he sought to the fundamental question of knowledge, for his dogmatic idealism denies, it is true, the reality of the external world, but admits with frivolous thoughtlessness that there are other minds outside of him, Berkeley, and even a universal mind. Thus, then, even according to him, the ‘I’ is not all; there is still something outside of the ‘I,’ a ‘not-I’; there does exist an external world, if only under the form of immaterial spirits. This, however, brings up the question, How does Berkeley’s ‘I’ come to conceive the existence of something outside of itself, the existence of a ‘not-I’? That was the question which had to be answered, and, in spite of its sacrificing the whole world of phenomena, Berkeley’s idealism, like the idealism of every one of his successors, makes no reply to it whatsoever.