Our experience of bodies here and now is that they are composed of material particles derived from the earth, whether they be bodies animated by vegetable or by animal forms of life. But I take it that the real meaning of the term 'body' is a _means of manifestation_,--perhaps a physical mode of manifestation adopted by something which without such instrument or organ would be in a different and elusive category. Why should we say that bodies must be made of matter? Surely only because we know of nothing else of which they could be made; but that lack of knowledge is not very efficient as an argument. True, if they were made of anything else they would not be apparent to us now, with our particular evolutionally-derived sense organs; for these only inform us about matter and its properties. Constructions built of Ether would have no chance of appealing to our senses, they would not be apparent to us; they would therefore not be what we ordinarily call bodies; at any rate they would not be material bodies. In order to become apparent to us, a psychical or vital entity must enter the material realm, and either clothe itself with, or temporarily assimilate, material particles. It may be that etherial bodies do not exist; the burden of proof rests upon those who conceive of their possible existence; but we are bound to admit that even if they did exist, they would make no impression on our senses. Hence if there are any intelligences in another order of existence interlocked with ours, and if they can in any sense be supposed to have bodies at all, those bodies must be made either of Ether or of something equally intangible to us in our present condition.[36] Yet, though intangible and elusive, we have reason to know that Ether is substantial enough,--far more substantial indeed than matter, which turns out to be a rare and filmy insertion in, or modification of, the Ether of Space; and a different set of sense organs might make the Ether eclipse matter in availability and usefulness. In my book _The Ether of Space_ this thesis is elaborated from a purely physical point of view. I wish, however, to make no assertion concerning the possible psychical use of the Ether of Space. Anything of that kind must be speculative; the only bodies we now know of in actual fact are material bodies, and we must be guided by facts. Yet we must not shut the door prematurely on other possibilities; and we can remember that inspired writers have sometimes contemplated what they term a spiritual body. PERMANENCE OF BODY