An image may make clearer what I mean, and I offer it only for this purpose, well knowing that “the best in this kind are but shadows.” Suppose that a man were enclosed in a sheath composed of metal having certain peculiar properties: it is opaque when cold, but when heated it becomes transparent, and the hotter it is the more transparent it grows. Such a substance might easily exist, at any rate it is entirely conceivable. We must assume in addition that the heat is not such as to be injurious to the occupant. Now a man enclosed in such a sheath would, when it was at the proper temperature, see what was going on around him; he could also be seen, he could hold communication with other men, and direct operations which he wished carried out. If the sheath, in addition to being transparent at the right temperature, were also, under the same conditions, flexible, and fitted him like a skin, he could do things himself. If it got cold, however, and thereby became, in the measure of its coolness, opaque and rigid, the man would be shut off from all communication or interaction with the world outside, he would be what we call dead.
I suggest that Consciousness with all its attendant phenomena is represented by the man, the sheath is Matter, the heat is Life. Matter, historically, precedes the manifestation of consciousness, but as it is never without a certain degree of life, so, even in the nebular form in which it exists before it has cohered into worlds and systems, it is not without the element of directivity, of harmonious inter-relation and interaction. A higher organization of life makes possible the subtler sensitiveness of the vegetable kingdom. The most vital, the most highly organized form of matter we know is the human brain and nervous system. Here the sheath has assumed a considerable degree of transparency and flexibility. But doubtless a far higher degree of organization is possible, and when this is reached the capacities of consciousness will have developed to an extent altogether inconceivable to us at present, though every now and then some exceptionally constituted individual gives us a hint of stages of development as yet far beyond the capacities of the race in general.