JOSEPH PETZOLDT, Philosophic der Rcinen Erfahrunj. : >!)."> processes of conscious activity to which he gives the name of Vital Series (Vitalreihcri), but which we should prefer to call, with Prof. Stout, interest-series. The second is the discovery of a new and simple principle for classifying and interpreting the tangled maze of mental phenomena. Avenarius superseded the familiar distinction of states of consciousness into sensations, cognitions, feelings, volitions by the much simpler and more general division into Elements on the one hand and Character- istics (Charakterc) on the other. These two discoveries taken together, adds Mr. Petzoldt, lead to the discovery of the true biological meaning of the central nervous system (p. 93). How it should do so is, of course, per- fectly inconceivable. Wundt's criticism that these translations of psychological fact into the terms of Biology are of no use either to Psychology or to the Physiology of the nervous system, that it is a purely formal schematism that could be applied to Herbart's ' Realen ' just as effectively as to the vital processes of the brain seems to me quite irresistible. It is only on the assumption that mental processes are inexplicable except through the determina- tive intervention of purely physical processes that the hypothesis of these organic Vitalreihen can be in any way justified. It is in every ordinary sense an illegitimate hypothesis. Ic professes to be a biological hypothesis, and yet it is framed not to fit the facts of Biology, but in the interests of Psychology ; it is further, so far as our present knowledge of the brain goes, completely unveri- fiable. Were it absolutely imperative to find for Psychology some determining ground outside the facts of the mental life, it would be welcome, and very welcome, as a temporary piece of scaffolding, and this is, of course, the consideration that makes Mr..Petzoldt's position intelligible. But we have yet to determine whether Psychology is not more independent than Mr. Petzoldt seems to think. For what after all is the force of our author's long argu- ment in proof of the indeterminateness of psychical activity? Does that which he has succeeded in proving really prove his point? I cannot see that it does. It has shown us that one psychical state cannot be said to determine the state that immedi- ately succeeds it in the same way as the position of a moving body at any moment is determined by the position it occupied at the previous instant. This is perfectly true, as his careful argu- ment clearly shows. But this only proves that psychical states as Mr. Petzoldt conceives them cannot determine each other as Mr. Petzoldt would have them do. We should be prepared to contend both that Mr. Petzoldt does not approach the facts of Psychology in such a way as to do justice to them, and that to be scientifically determinable a psychical fact need not be uni- determinable in the sense of Mr. Petzoldt. Let us first try and see what the precise psychological attitude of Avenarius and of our author really is. Mr. Petzoldt holds that the most important psychological dis-
