The chief feature of the book is therefore M. Fouillée's criticisms of the theories "that make consciousness the intermittent illumination of a mechanism"; of the theories "that reduce the sentiments and the emotions to simple reverberations of organic movements and even of expressive movements"; of those finally "that make of desire and the feeling of effort, simple passive muscular sensations, the reflexions of movements already executed." Solid objections are not wanting in these pages. M. Fouillée does not refrain from playing when he has a good hand. So far so good. But—we ask—would psychology have ever made any advances if it lacked the hypothesis that M. Fouillée condemns? And, as a matter of fact, are the majority of psychologists really thus irretrievably bent upon establishing a mechanical explanation of life, a theory of "man as automaton"? The truth of the matter is that the opposed point of view has rendered no results, and that in taking consciousness for our central position we too easily go astray in fanciful speculations. On the other hand, by the endeavor to grasp the bonds of mind through the medium of the body, it _has_ been found possible to throw some light upon unobserved facts. It would not do to let this be too quickly forgotten; and if some have seen fit to pass beyond and to attempt to reduce the Universe to a mechanism, imprudent saltations of this character into open materialistic metaphysics concern them alone. Will M. Fouillée be more fortunate in his reduction of the world to idealism? It yet appears doubtful. The definition of 'idea-forces' presents at the outset elements of embarrassment. That every idea, every mental image, however absolutely an image it may be, of emotions or of passions, always contains some motor elements, and consequently acts like a force, is easily comprehended, and every body allows it. When physiologists speak of the power of ideas, they mean nothing else. But beyond that we cannot go. The idea, in M. Fouillée's sense, is every state of consciousness. Now, all the facts of consciousness are reducible to the following elementary connected process: sensation, perceptual excitation, reaction; and the three factors of this process cannot be separated or reduced to one. Every idea, or state of consciousness, is accordingly the source of motion since it contains desire. Desire is basal to the nervous act; the nervous act does not precede and does not explain the higher states that psychologists, viewing things from a different point of view, have regarded as epiphenomena. The essence, not only of man, but also of the world, is desire. The idea-force, "the abridged formula of the appetitive process," becomes the shaper of universal evolution, and, in a word, the physical is a reflection of the psychical. Such are, if I am not deceived, the chief propositions of the work, put into a logical form, from which no doubt you will judge that the facts do not correspond without evident hiatus.