FIFTH BOOK
IMMANUEL KANT AND THE CRITICAL PHILOSOPHY
We have found investigations into the nature of knowledge as early as the philosophers of the Renaissance and in the great system builders. But they were nevertheless decidedly under the spell of the constructive tendency. As a result of the English empirical philosophy regarding the investigation of knowledge as the distinctive problem of philosophy, we have the extreme statement of the problem by Hume. It was this statement of the problem that furnished the occasion which led Kant to undertake a comprehensive investigation of the conditions and presuppositions of our knowledge and of our mental functions in general. Such an investigation constitutes the task of what he has called the Critical Philosophy. The critical philosophy has nothing to do with a theory of the evolution of knowledge, in the modern sense of the word. Its distinctive task is to discover the necessary principles which must be presupposed—howsoever human nature may be constituted—if a mental function, no matter whether it be cognition, aesthetic or ethical evaluation, or religious trust, is to attain any valid results. It investigates the conditions of the validity of knowledge, not those of its origin. The success of and the purely scientific element contained in this philosophy consists in its penetrating beneath the finished products and results of the human mind to their efficient causes. Just as we can only understand a man's real nature by penetrating beneath his outward acts to his real character, so likewise the only way
