The first step towards the reduction of these two factors to one may obviously be made in three different ways. Either the _ego_ may be represented as a mode of the _non-ego_, or the _non-ego_ of the _ego_, or both of a _tertium quid_, distinct from either. In other words: it may be maintained, _first_, that matter is the only real existence; mind and all the phenomena of consciousness being really the result solely of material laws; the brain, for example, secreting thought as the liver secretes bile; and the distinct personal existence of which I am apparently conscious being only the result of some such secretion. This is _Materialism_, which has then to address itself to the further problem, to reduce the various phenomena of matter to some one absolutely first principle on which everything else depends. Or it may be maintained, _secondly_, that mind is the only real existence; the intercourse which we apparently have with a material world being really the result solely of the laws of our mental constitution. This is _Idealism_, which again has next to attempt to reduce the various phenomena to some one immaterial principle. Or it may be maintained, _thirdly_, that real existence is to be sought neither in mind as mind nor in matter as matter; that both classes of phenomena are but qualities or modes of operation of something distinct from both, and on which both alike are dependent. Hence arises a third form of philosophy, which, for want of a better name, we will call _Indifferentism_, as being a system in which the characteristic differences of mind and matter are supposed to disappear, being merged in something higher than both. In using the two former of these terms, we are not speaking of Materialism and Idealism as they have always actually manifested themselves, but only of the distinguishing principle of these systems when pushed to its extreme result. It is quite possible to be a materialist or an idealist with respect to the immediate phenomena of consciousness, without attempting a philosophy of the Unconditioned at all. But it is also possible, and in itself natural, when such a philosophy is attempted, to attempt it by means of the same method which has approved itself in relation to subordinate inquiries; to make the relation between the human mind and its objects the type and image of that between the universe and its first principle. And such attempts have actually been made, both on the side of Materialism and on that of Idealism; and probably would be made oftener, did not counteracting causes frequently hinder the logical development of speculative principles.