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To every aspect of the problem Herbert Spencer must have given thought; but he has plainly declared that the human intellect, as at present constituted, can offer no solution.  The greatest mind that this world has yet produced—­the mind that systematized all human knowledge, that revolutionized modern science, that dissipated materialism forever, that revealed to us the ghostly unity of all existence, that reestablished all ethics upon an immutable and eternal foundation,—­the mind that could expound with equal lucidity, and by the same universal formula, the history of a gnat or the history of a sun—­confessed itself, before the Riddle of Existence, scarcely less helpless than the mind of a child.

But for me the supreme value of this last essay is made by the fact that in its pathetic statement of uncertainties and probabilities one can discern something very much resembling a declaration of faith.  Though assured that we have yet no foundation for any belief in the persistence of consciousness after the death of the brain, we are bidden to remember that the ultimate nature of consciousness remains inscrutable.  Though we cannot surmise the relation of consciousness to the unseen, we are reminded that it must be considered as a manifestation of the Infinite Energy, and that its elements, if dissociated by death, will return to the timeless and measureless Source of Life....  Science to-day also assures us that whatever existence has been—­all individual life that ever moved in animal or plant,—­all feeling and thought that ever stirred in human consciousness—­must have flashed self-record beyond the sphere of sentiency; and though we cannot know, we cannot help imagining that the best of such registration may be destined to perpetuity.  On this latter subject, for obvious reasons, Herbert Spencer has remained silent; but the reader may ponder a remarkable paragraph in the final sixth edition of the “First Principles,”—­a paragraph dealing with the hypothesis that consciousness may belong to the cosmic ether.  This hypothesis has not been lightly dismissed by him; and even while proving its inadequacy, he seems to intimate that it may represent imperfectly some truth yet inapprehensible by the human mind:—­

“The only supposition having consistency is that that in which consciousness inheres is the all-pervading ether.  This we know can be affected by molecules of matter in motion, and conversely can affect the motions of molecules;—­as witness the action of light on the retina.  In pursuance of this supposition we may assume that the ether, which pervades not only all space but all matter, is, under special conditions in certain parts of the nervous system, capable of being affected by the nervous changes in such way as to result in feeling, and is reciprocally capable under these conditions of affecting the nervous changes.  But if we accept this explanation, we must assume that the potentiality of feeling is