4. The Empirical Prejudice in Helmholtz. — The same empirical prejudice recurs in Helmholtz,[1] who admits causality as the one and only a priori form, but treats it as a species of instinct or impulsive tendency, a purely subjective affair of whose necessity and universality there can in consequence be no guarantee. It is evident that this view of the a priori more nearly approaches the mental attitude of the English empiricists than the category of Kant as a condition essential to the intelligibility of the real; it is a law of our nature from which there is no escape, and which for that very reason must ever be to us an obscure and mysterious power for which we can in no wise account. How can a principle which is blind and incomprehensible in itself help us to interpret experience? Above all, what value has the science to which this need gives birth unless it be that of a contingent and subjective construction? The results of the researches of Helmholtz, which seemed to him to contradict Kant’s[2] theories on certain points, inclined him to adopt the views of Stuart Mill, and even those expressed earlier by Hume and Berkeley. Intuition a priori, the universal necessity of mathematical truths, is excluded by the fact that perception of space is not inborn but acquired in the course of a slow process of experience, and more especially by the fact that it is possible to conceive of a space other than that of which Euclid treats in his geometry.[3] We will leave to the second part of this book the discussion of the value of the new geometrical speculations and the alleged proof that the empiricists have deduced therefrom in support of their teaching; for the present we will content ourselves with pointing out that Helmholtz clearly fails to distinguish between the epistemological and the psycho-physiological a priori, with the result that his analyses of perception prepare the way for the phenomenalism of Mach and Avenarius.
5. Liebmann and Schultze. — The philosophers of
the neo-Kantian school were not, however, all thus
led astray. Liebmann draws a sharp distinction between
