foundation from theism, he opened, on the other hand, the way to entirely different and more profound explanations of existence. In the chapter on the ultimate aim of the natural dialectic of reason it is asserted that the three transcendent Ideas are of value as regulative principles for the advancement of the knowledge of nature. But Kant can barely have been serious in making this assertion. At least its opposite, that these assumptions are restrictive and fatal to all investigation of nature, is to every natural philosopher beyond doubt. To test this by an example, let any one consider whether the assumption of the soul as an immaterial, simple, thinking substance would have been necessarily advantageous or in the highest degree impeding to the truths which Cabanis has so beautifully expounded, or to the discoveries of Flourens, Marshall Hall, and Ch. Bell. Indeed Kant himself says (_Prolegomena_, § 44), “The Ideas of the reason are opposed and hindering to the maxims of the rational knowledge of nature.” It is certainly not the least merit of Frederick the Great, that under his Government Kant could develop himself, and dared to publish the “Critique of Pure Reason.” Hardly under any other Government would a salaried professor have ventured such a thing. Kant was obliged to promise the immediate successor of the great king that he would write no more. ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ I might consider that I could dispense with the criticism of the ethical part of the Kantian philosophy here because I have given a detailed and thorough criticism of it twenty-two years later than the present work in the “_Beiden Grundproblemen der Ethik_.” However, what is here retained from the first edition, and for the sake of completeness must not be omitted, may serve as a suitable introduction to that later and much more thorough criticism, to which in the main I therefore refer the reader.