[7] See my Outlines of Cosmic Philosophy, Vol. II. pp. 142-148. The essential weakness of such a theory as this lies in the fact that it is thoroughly materialistic in character. It is currently assumed that the doctrine of a life after death cannot be defended on materialistic grounds, but this is altogether too hasty an assumption. Our authors, indeed, are not philosophical materialists, like Dr. Priestley,--who nevertheless believed in a future life,--but one of the primary doctrines of materialism lies at the bottom of their argument. Materialism holds for one thing that consciousness is a product of a peculiar organization of matter, and for another thing that consciousness cannot survive the disorganization of the material body with which it is associated. As held by philosophical materialists, like Buchner and Moleschott, these two opinions are strictly consistent with each other; nay, the latter seems to be the inevitable inference from the former, though Priestley did not so regard it. Now our authors very properly refuse to commit themselves to the opinion that mind is the product of matter, but their argument nevertheless implies that some sort of material vehicle is necessary for the continuance of mind in a future state of existence. This material vehicle they seek to supply in the theory which connects by invisible bonds of transmitted energy the perishable material body with its counterpart in the world of ether. The materialism of the argument is indeed partly veiled by the terminology in which this counterpart is called a "spiritual body," but in this novel use or abuse of scriptural language there seems to me to be a strange confusion of ideas. Bear in mind that the "invisible universe" into which energy is constantly passing is simply the luminiferous ether, which our authors, to suit the requirements of their hypothesis, have gratuitously endowed with a complexity and variety of structure analogous to that of the visible world of matter. Their language is not always quite so precise as one could desire, for while they sometimes speak of the ether itself as the "unseen universe," they sometimes allude to a primordial medium yet subtler in constitution and presumably more immaterial. Herein lies the confusion. Why should the luminiferous ether, or any primordial medium in which it may have been generated, be regarded as in any way "spiritual"? Great physicists, like less trained thinkers, are sometimes liable to be unconsciously influenced by old associations of ideas which, ostensibly repudiated, still lurk under cover of the words we use. I fear that the old associations which led the ancients to describe the soul as a breath or a shadow, and which account for the etymologies of such words as "ghost" and "spirit," have had something to do with this spiritualization of the interstellar ether. Some share may also have been contributed by the Platonic notion