13. It may be objected that such a conception of the facts supposes that will (and conscious thought) are physical energies--for however _slight_ we make this energy, it is still energy none the less. The air which closed the door would not move it _of itself_--unless some pressure were exerted upon it from without. Could "life" act otherwise? One reply to this objection is that the distinguishing characteristic of life is this very power of original, spontaneous movement. It is life, and life alone, which possesses this power. Were this doctrine true, it would of course upset the present theory of the Conservation of Energy, for it would admit the constant infusion into the world of energy from without. Despite the theoretical difficulty thus presented, it seems probable that life is, in a certain sense, a physical energy, or at least its manifestation is. It is possible that the two states are similar to the difference between potential and kinetic energy; and we must remember that _energy is always noticed or experienced by us, as energy, in its expenditure, never in its accumulation_.[8] If life be a physical force, if vitality be a specific energy, then, it seems to me, many things fall into line--many phenomena, hitherto inexplicable, become at once intelligible. Let me illustrate this conclusion by mentioning a few such facts: Take, for instance, the phenomena manifested in the presence of Eusapia Palladino. I shall not now stop to discuss the reality of these manifestations, because I consider them just as certain as any other facts in life, and not at all open to discussion. Now, in these phenomena there is an intelligence _of some sort_ at work producing them; that is certain. But as to the _nature_ of this intelligence--_what_ it is--that is altogether another matter, and a much more difficult question to answer. Whether this be a low order of deceiving and "lying spirits," as Professor Barrett and others are apparently inclined to believe, or whether it be a fraction of the medium's own mind (Flournoy, Morselli), or whether it be the spirit it claims to be, or whether it belongs to some other even more doubtful order of intelligence, such as postulated by the Theosophists and certain Mystics and Occultists, _that_ is a question which we cannot at present answer, and for which we may have to wait for several hundred years before one can be satisfactorily given. But, granting the reality of the phenomena, they themselves demand solution, solely from the point of view of physics and physiology, and quite aside from the nature of the intelligence with which they are at times associated. The facts themselves still need elucidation.