I. Haeckel and His Opponents

Such objections point to a misunderstanding of the view of the world which Haeckel represents. Anyone who has really been saturated with the spirit of this view will never seek to explore the laws of mental life by any other road than by inner experience, by self-observation. The opponents of the scientific mode of thought talk exactly as if its supporters sought to discover the truths of logic, ethics, aesthetics, and so forth, not by means of observing mental phenomena as such, but from the results of brain-anatomy. The caricature of the scientific world-conception thus created by such opponents for themselves is then termed materialism, and they are untiring in ever repeating afresh that this view must be unproductive, because it ignores the mental side of existence, or at least gives it a lower place at the expense of the material. Otto Liebmann, whom we may here cite once more, because his anti-scientific conceptions are typical of the mode of thought of certain philosophers and laymen, observes: “But granting, however, that natural science had attained its goal, it would then be in a position to show me accurately the physico-organic reasons why I hold that the assertion ‘twice two are four’ is true and assert it, and the other assertion ‘twice two are five’ is false and combat it, or why I must, just at this moment, write these very lines on paper the while I am entangled in the subjective belief that this happens because I will to write them down on account of their truth as assumed by me” ( Thoughts and Facts, pt. ii, p. 294 et seq.). No scientific thinker will ever be of opinion that bodily-organic reasons can throw any light upon what, in the logical sense, is true or false. Mental connections can only be recognised from the side of the mental life. What is logically justified, must always be decided by logic; what is artistically perfect, by the aesthetic judgment. But it is an altogether different question to inquire: How does logical thinking, or the aesthetic judgment arise as a function of the brain? It is on this question only that comparative physiology and brain-anatomy have anything to say. And these show that the reasoning consciousness does not exist in isolation for itself, only utilising the human brain in order to express itself through it, as the piano-player plays on the piano; but that our mental powers are just as much functions of the form-elements of our brain, as “every force is a function of a material body” (Haeckel, Anthropogenesis, pt. ii, p. 853).