The whole difficulty has arisen, it seems to me, because of the conception of the nature of life usually held. Were this altered these problems would be found to have a ready solution. M. Bergson has gone half way toward finding this solution, but has stopped there; he has clung to the most fallacious part of the theory, and for this reason has been unable to emerge altogether from the difficulties above mentioned. Only when we change our conception of the nature of the life-force will these problems become clearer--these questions find their true solution. Have I, then, any theory to offer as to the nature of this power of life which is essentially new to physiology and biology? I believe that I have--not new as to facts, but as to the interpretation of facts (the latter remain the same on either theory). In order to make the theory which follows plain in as few words as possible, it will be necessary to refer for a moment to the current conception of vital energy--of life--in the human body. It has been stated by Bergson himself with admirable clearness (_Hibbert Journal_, October 1911, pp. 35-36; _Creative Evolution_, pp. 253-54, etc.), and is briefly this: Food, when broken down and oxidised in the body, gives forth or liberates energy--just as coal liberates energy when burned in the engine. In both cases energy (contained in the food or the coal, as the case may be) is liberated, and this energy is utilized to drive our engine--the human body or the steam-engine (it makes no difference to the argument). The energy thus gained is, it is contended, again given off as heat and work--muscular and mental work in the case of the human engine (the body); mechanical work of all sorts, and heat, in the case of the steam-engine. Thus one is essentially no more mysterious than the other--the body no more so than the steam-engine--vitality no more so than steam! Both are "physical" energies, subject to the law of conservation, and as such transmutable one into the other. This is the generally accepted theory, which likens the human body to a steam-engine, and is the theory all but universally adopted by scientific men, held as proved and adopted without question by M. Bergson! But such a view of the case is, I believe, essentially untrue. It is _one_ interpretation of the observed facts, truly; but not the only interpretation. The facts remain equally true on either theory; the difference lies in their explanation. It is the old error of confusing coincidence with causation--and not only that, but a particular _kind_ of causation, and "treating it as the only imaginable kind." Just as the psychologists reasoned upon the acknowledged facts of the relation of brain and consciousness; so do the physiologists, in our own day, reason upon this question of the causation of vital energy by food. In both cases there has been one-sided and partial reasoning.