'We know that with the very first awakening of knowledge, man is confronted with two obvious facts:
The existence of the world in which he lives; and the existence of psychic life in himself.
Neither of these can he prove or disprove, but they are facts: they constitute reality for him.
It is possible to meditate upon the mutual correlation of these two facts. It is possible to try to reduce them to one; that is, to regard the psychic or inner world as a part, reflection, or function of the world, or the world as a part, reflection, or function of that inner world. But such a procedure constitutes a departure from facts, and all such considerations of the world and of the self, to the ordinary non-philosophical mind, will not have the character of obviousness. On the contrary the sole obvious fact remains the antithesis of I and Not-I — our inner psychic life and the outer world.'