536 CEITICAL NOTICES I Geist und Korper, Seek und Leib. Von LUDWIG BUSSE. Leipzig, 1903. Pp. x, 488. THE main object of this book is a thorough- going criticism of the doctrine of psycho-physical parallelism, but this is preceded by a refutation of materialism on other than purely epistemological grounds, and followed by an indication of the view of the world accepted by the author along with the counter doctrine of inter- action. Prof. Busse discovers in his opponents a disingenuous tendency to take refuge in idealistic monism, whenever their theory lands them in a difficulty, which forgets that, in the light of the highest metaphysical reflexion, parallelism and interaction are alike in a certain sense fictions. The only question to be decided is, which gives the best explanation of empirical reality. Parallelism, leaving unchallenged opinions with which scientific investigation thinks it cannot part, gives an answer more congenial to science than interaction, which finds it difficult Prof. Busse finds it impossible to accept the principle of the conservation of energy. But, after all, philosophy is not the handmaid of science bound to homologate all its pet ideas, and, while the physiologist as such would gain nothing by the recognition of psychical pro- cesses that do not admit of mechanical construction, the philosopher as such would gain nothing by the resolution of the whole world into a mechanism of atoms. He would be quite incapable of comprehending the meaning of their endless combinations, even if every one of them were exactly calculable. Interaction does really help us to some comprehension of the relation between body and soul, and it does not necessarily imply the destruction of all science. Only in some, not strictly determined, still in a sense defined points, science would require to admit psychical events as causes or effects. It is not a necessity of thought that every physical event should be physically explicable, it is not an incontestable induction from the facts of experience, it is a mere hypothesis, which, so long as the actions of a man have not got their mechan- ical explanation, is illegitimately assumed to be universally valid. And pretty much the same is true of the principle of the con- servation of energy. In agreement with Wundt, Prof. Busse distinguishes two moments in this principle, that of equivalence and that of constancy, and he sees no objection to regarding the principle of equivalence as a law resting upon experience, quite justifiably universalised and perfectly reconcilable with interaction ; but, of course, if there is an exchange of activities between physical and psychical factors, the sum of energy in the physical world cannot remain constantly the same. That it does so, although raised to be the most universal principle of the investigation of nature, is a valid hypothesis only under the undemonstrable assumption that nature is one closed system. Such propositions are not regulated by the world, but by the thinking of a number of physicists, whose convenient assumptions philosophers are foolish
