5 26 THE HISTORY OF BIOLOGY 



"He is an ontological pluralist in that he conceives nature to be a multi- 

 plicity of separate substances (atoms), a metaphysical dualist in so far as 

 he assumes in every substance two combined metaphysical principles (en- 

 ergy and matter); a phenomenal dualist in that he assumes two distinct 

 spheres of phenomena (external mechanical happening, and internal sensa- 

 tion and will), a hylozoist because he ascribes to all matter the possession 

 of life and soul; further, he is a philosopher of identity, a cosmonomistic 

 monist, and a materialist." Thus the Haeckelian monism, if closely looked 

 into, will be found to contain a little of everything. It may therefore be 

 worth pointing out in this connexion that even more deeply elaborated mo- 

 nistic systems have appeared in our own day. As a matter of fact, monism as 

 a philosophical view of life is a comparatively ancient doctrine; the neo- 

 Platonists, who ascribed true existence only to ideas, were undeniably 

 monists, as was also Spinoza, and so, too, Schelling and his successors, in- 

 cluding both Goethe and Hegel. Monism based on natural-scientific grounds, 

 however, has undoubtedly become an especially widespread conception in 

 modern times. As one of its leading representatives may be mentioned Ernst 

 Mach (i 838-191 6), professor originally of physics and then of philosophy 

 at Vienna. As a physicist he applied himself, inter alia, to mental-physio- 

 logical studies after the pattern of Helmholtz, but he also studied Kant's 

 writings and was led through them into the sphere of the theory of knowl- 

 edge. He thereupon felt himself called upon .to create a method of scientific 

 thinking, not as a philosopher, for he was unwilling to call himself that, 

 but as a student of science. He will have nothing to do with transcendent 

 spheres of thought. Through the analysis of different sense-impressions he 

 came to the conclusion that everything is phenomenal; nothing exists in 

 itself; the outer world consists of a series of phenomena, and the ego, the 

 personality, likewise of a series of phenomena, which we call perceptions; 

 the phenomena stand in a relation to one another, which is expressed by 

 the functional terms of mathematics: one change brings about another; the 

 phenomena inside and outside the personality are mutually interdependent. 

 Mach denies the principiant contrast between appearance and reality; the 

 most fantastic dream is just as much a phenomenon as a real event; he like- 

 wise denies the contrast between ego and non-ego, for both are a series of 

 mutually interdependent phenomena. The manner in which Mach explains 

 on these postulates such phenomena as will and thought has been much dis- 

 cussed by philosophers who have made a special study of the subject, and 

 has often been characterized as lacking in seriousness: by Hoffding, for in- 

 stance, who points out that the elements common to physics and physiology 

 are in Mach indefinite and mystical, like a shapeless nebula. Now, Mach, 

 as already mentioned, claims to be only a natural scientist and to try to 

 solve only natural-scientific thought-problems. But even as such he exposes 



