I can hardly too often repeat that my object in these pages is of a quite opposite character. Believing that all cognisable Mind is as continuous as all cognisable Matter, my ideal would be to attempt for the realm of mind what the spectroscope and the law of gravitation have effected for the realm of matter, and to carry that known cosmic uniformity of substance and interaction upwards among the essences and operations of an unknown spiritual world. And in order to explore these unreachable altitudes I would not ask to stand with the theologian on the summit of a "cloud-capt tower," but rather on plain earth at the measured base of a trigonometrical survey. If we would measure such a base, the jungle must be cleared to begin with. Let us move for a while among first definitions; trying to make clear to ourselves what kind of thing it is that we are endeavouring to trace or discover. In popular parlance, we are looking out for _ghosts_. What connotation, then, are we to give to the word "ghost"--a word which has embodied so many unfounded theories and causeless fears? It would be more satisfactory, in the present state of our knowledge, simply to collect facts without offering speculative comment. But it seems safer to begin by briefly pointing out the manifest errors of the traditional view; since that tradition, if left unnoticed, would remain lodged in the background even of many minds which have never really accepted it. Briefly, then, the popular view regards a "ghost" as a _deceased person permitted by Providence to hold communication with survivors_. And this short definition contains, I think, at least three unwarrantable assumptions. In the first place, such words as _permission_ and _Providence_ are simply neither more nor less applicable to this phenomenon than to any other. We conceive that all phenomena alike take place in accordance with the laws of the universe, and consequently by permission of the Supreme Power in the universe. Undoubtedly the phenomena with which we are dealing are in this sense permitted to occur. But there is no _a priori_ reason whatever for assuming that they are permitted in any especial sense of their own, or that they form exceptions to law, instead of being exemplifications of law. Nor is there any _a posteriori_ reason for supposing any such inference to be deducible from a study of the phenomena themselves. If we attempt to find in these phenomena any poetical justice or manifest adaptation to human cravings, we shall be just as much disappointed as if we endeavoured to find a similar satisfaction in the ordinary course of terrene history.