58 LECTURES ON BIOLOGY 



phenomena of evolution easily leads to the conclusion that with 

 the perfection of the physical organization an increase takes place 

 in the psychic activities, we meet with the still current belief 

 that the former is the cause of the latter. But a deeper insight 

 into the evolution of psychical phenomena leads to the opposite 

 belief; through the motion which it causes the stimulus reacts 

 upon the physical organization, and leaves behind in it those 

 permanent traces which facilitate at first the renewal of the 

 stimulus-motion (Triebewegung], and then, when the reactions 

 of other stimulus-actions are added, permits the origination of 

 more complex stimulus-expressions." We are even " impelled to 

 believe that the physical development is not the cause but the 

 effect of the psychic development." In fact, without this 

 assumption an understanding of the purposefulness of the life- 

 phenomena is impossible. It will be clear that this statement 

 is only apparently anti-mechanical, for the postulated psychic 

 energy does not represent something imperceptible like the vital 

 force, but is like every other form of energy definable quan- 

 titatively and thus perceivable scientifically. 



If we now attempt to define the aim and object of modern 

 biology we shall say that they consist in reducing all functional 

 processes comprised in the term "life" to chemico-physical 

 causes. But only when we have succeeded in reducing an 

 organism to simple mathematical formulae, to predetermine its 

 life-phenomena, changes, &c., just as the astronomer calculates 

 the course of the stars and predicts eclipses of the sun and 

 moon accurately to the minute, only then can we claim to have 

 satisfied this demand. That this goal is as yet far distant, that 

 neither modern chemistry nor physics is able to perform this 

 task, and that in the end we shall only be able to approach our 

 aim but never reach it, need not be specially mentioned. The 

 phenomena of life are so many, the structure and conditions of 

 the living substance so exceedingly complex, that in the majority 

 of cases we shall have to be content with a mere description, 

 because no explanation is available. 



But however far we may be privileged to penetrate into 

 the mysteries, one will always remain hidden consciousness. 

 We may possess a perfect knowledge of the structure of the 



