... The ego can only be conscious of itself and of its modifications. That which does not touch it in any way remains unknown. Now, the modifications of the ego may be reduced to two groups. The one comes to it from without, representing the action of things upon it; these are sensations. The other springs up within, representing the action of the ego on things, its spontaneous energy, its volitions, and its acts. Thence come the two constituent elements of every consciousness, the distinction between object and subject, the ego and the non-ego, thought and the object of thought. We call _objective_ every idea or quality that it is possible to refer to the object alone, independently of the action or disposition of the subject. We call _subjective_ all knowledge implying identity of subject and object, all discipline bearing on the rules of the spontaneous activity of the ego, since without that activity the rules which should direct it would not exist. In the first case we are conscious of a distinction and even of a radical opposition between the object and the subject of knowledge; in the second, we are conscious of their fundamental identity in this sense, that the thinking and willing subject presents itself to itself as an object of thought and study. In order that the two orders of knowledge, engendered by this duality of origin, may be brought into logical unity, it is necessary either that the subject should enter into the object, that the ego should be absorbed by the non-ego, so that the laws of the non-ego should become the laws of the ego--and that would be materialism; or that the object should enter into the subject so that the laws of the subject should become the law of things--and that would be idealism. Outside these two systems, equally violent and absolute, the two orders of knowledge are irreducible, because in us the consciousness of the ego and the consciousness of the world are at present in conflict. Morality is neither reconciled to science, nor science to morality. In their _rapprochement_, progressive to infinity, a hiatus always subsists.