Closely allied to speculations such as these is another speculation, more capable of subjection to experimental test, yet which remains still inconclusively tested, and which has become for many reasons a stumbling-block rather than a corroboration in the spiritual inquiry. I refer to the question whether any influence is exercised by spirits upon the gross material world otherwise than through ordinary organic structures. We know that the spirit of a living man controls his own organism, and we shall see reason to conclude that discarnate spirits may also control, by some form of "possession," the organisms of living persons,--may affect directly, that is to say, some portions of matter which we call living, namely, the brain of the entranced sensitive. There seems to me, then, no paradox in the supposition that some effect should be produced by spiritual agency--possibly through the mediation of some kind of energy derived from living human beings--upon inanimate matter as well. And I believe that as a fact such effects have been observed and recorded in a trustworthy manner by Sir W. Crookes, the late Dr. Speer, and others, in the cases especially of D. D. Home and of W. Stainton Moses. If, indeed, I call these and certain other records still inconclusive, it is mainly on account of the mass of worthless narratives with which they have been in some sense smothered; the long history of so-called investigations which have consisted merely in an interchange of credulity and fraud. For the present the evidence of this kind which has real value is better presented, I think, in separate records than collected or discussed in any generalised form. All that I purpose in this work, therefore, is briefly to indicate the relation which these "physical phenomena" hold to the psychical phenomena with which my book is concerned. Alongside of the faculty or achievement of man's ordinary or supraliminal self I shall demarcate the faculty or achievement which I ascribe to his subliminal self; and alongside of this again I shall arrange such few well-attested phenomena as seem _primâ facie_ to demand the physical intervention of discarnate intelligences. I have traced the utmost limits to which any claim to a scientific basis for these inquiries can at present be pushed. Yet the subject-matter has not yet been exhausted of half its significance. The conclusions to which our evidence points are not such as can be discussed or dismissed as a mere matter of speculative curiosity. They affect every belief, every faculty, every hope and aim of man; and they affect him the more intimately as his interests grow more profound. Whatever meaning be applied to ethics, to philosophy, to religion, the concern of all these is here.