What is a body, extension, movement, colour, smell and taste? What do I possess of them, or know of them, except through the images, sensations and feelings which they call up in my receptive mind? No single thing wanders into me as itself, or reveals itself to me directly; only through the way in which they affect me, the peculiar changes which they work in me, do things reveal to me their existence and their special character. I have no knowledge of an apple-tree or of an apple, except through the sense perceptions they call up in me. But these sense perceptions, what are they but different peculiar states of my consciousness, peculiar determinations of my mind? I see that the tree stands there, but what is it to see? What is the perception of a colour, of light, of shade, and their changes? Surely only a peculiar change of my mind itself, a particular state of stimulus and awareness brought about in myself. And in the same way I can feel that the apple lies there. But what is the perception of resistance, of hardness, of impenetrability? Nothing more than a feeling, a change in my psychical state, which is unique and cannot be described in terms of anything but itself. Even as regards “attraction and repulsion,” external existence only reveals itself to us through changes in the mind and consciousness, which we then attribute to a cause outside ourselves. It is well enough known that this simple but incontrovertible fact has often led to the denial of the existence of anything outside of ourselves and our consciousness. But even if we leave this difficult subject alone, it is quite certain that, if the question as to the pre-eminence of consciousness and its relation to external things is to be asked at all, it should be formulated as follows, and not conversely: “How can I, starting from the directly given reality and certainty of consciousness and its states, arrive at the certainty and reality of external things, substances, forces, physics and chemistry?” Creative Power of Consciousness.