Page:Mind (New Series) Volume 12.djvu/124

110 CRITICAL NOTICES : psychologist that the great need of psychology is to get rid of the big books. This may seem a hard saying, but the truth implied is that what is most needed is not the expression of the opinions of every thinker of any originality on all the problems of psychol- ogy, but rather the close and detailed study of narrowly denned problems by individual workers ; that the definite and final estab- lishment of one grain of psychological truth is a more desirable product of years of strenuous labour than a large volume filled with the reflexions and opinions upon a great range of topics of an author, no matter how able he may be. The treatment of ' Sensation ' is naturally brief. The section on Thought makes up nearly half the volume. Of this section the most valuable part is that which treats of delusion, which is de- fined as ' the spontaneous alteration of the cohesion of a relation without the aid of experience '. It is laid down that ' alteration and exaggeration of emotion precedes delusion,' and the interesting suggestion is made that the underlying structural change is of the nature of a ' parasitic mechanism ' and may come about ' by the independent and quasi-parasitic formation of nervous connexions, which may take place during sleep, and which are not necessarily attended by any mode of consciousness.' A classification or scale of delusions, according to the degree of departure from the normal, is suggested and should be of practical value to the alienist. In the earlier part of this section on ' Thought ' Dr. Mercier has ont held fast (it may be doubted whether he has grasped) the distinction between logic and psychology and is led into some prolonged discussions that can hardly be regarded as an essential part of the book. It would hardly seem to be necessary at this time of day to slay again the syllogism as a normal reasoning process and to investigate the mortality of Socrates once more. We may agree with Dr. Mercier's statement that the underlying principle of the syllogism and of all axiomatic reasoning is the assimilation of relations, but when he tells us that " It is one of the most curious anomalies of human faculty that Mill should have attributed to the syllogism the establishment of relations of coexistence and non-coexistence " one is tempted to remind him that " there are nine and sixty ways of constructing tribal lays, and every single one of them is right ". The section on ' Volition ' begins with a definition of Attention " with the emission of motion from the highest nerve regions occurs the corresponding mental state of attention " " When the amount of incoming motion is great in proportion to the amount evoked and emitted upon its reception, then the intensification of the sensation is slight, the awareness of activity is slight, and then the Attention is termed Eeflex Attention. When the amount of motion evoked by stimulus is great in proportion to the stimulus, then the intensification of Sensation is great, and the awareness of activity is great, and then this awareness is termed Voluntary Attention." This is in the last degree unsatisfactory ; in the first