It is evidently very enticing to make of the Ego thus a primitive notion of the consciousness; but this view of the Ego as opposed to the non-Ego in no way corresponds to that of the mental and the physical. The notion of the Ego is much larger, much more extensible, than that of the mental; it is as encroaching as human pride, it grasps in its conquering talons all that belongs to us; for we do not, in life, make any great difference between what is _we_ and what is _ours_--an insult to our dog, our dwelling, or our work wounds us as much as an insult to ourselves. The possessive pronoun expresses both possession and possessor. In fact, we consider our body as being ourselves. Here, then, are numbers of material things introducing themselves into the category of mental things. If we wished to expel them and to reduce the domain of the Ego to the domain of the mental, we could only do so if we already possessed the criterion of what is essentially mental. The notion of the Ego cannot therefore supply us with this criterion. Another opinion consists in making of the subject a spiritual substance, of which the consciousness becomes a faculty. By substance is understood an entity which possesses the two following principal characteristics, unity and identity, this latter merging into unity, for it is nothing else but the persistence of unity through the course of time. Certain philosophers have asserted that through intuition we can all establish that we are a spiritual substance. I am compelled to reject this idea, because I think the expression _spiritual substance_ has no meaning; nothing but the sonorous value of six syllables. It has also been supposed, that there exists a corporeal substance hidden under the sensations, in which are implanted the qualities of bodies, as the various organs of a flower are in its calyx. I will return later to this conception of a material substance. That of a spiritual substance cannot be defended, and the chief and fatal argument I urge against it is, that we cannot represent it to our minds, we cannot think it, and we cannot see in these words "spiritual substance" any intelligible idea; for that which is mental is limited to "that which is of the consciousness." So soon as we endeavour to go beyond the fact of having consciousness to imagine a particular state which must be mental, one of two things happen; either we only grasp the void, or else we construct a material and persistent object in which we recognise psychical attributes. These are two conclusions which ought to be rejected. FOOTNOTES: