In the year 1792 Kant administered a shock to some of his admirers. He published in the Berlinische Monatsschrift an essay which bore the ominous title On the Radical Evil in Human Nature. The shock was repeated in the following year, when this essay was republished, as the first and in many years the crucial part, of Kant's long-awaited work in the philosophy of religion, Religion within the Bounds of Reason Alone.

Kant's Fundamental Principles of the Metaphysics of Morals had appeared in 1785, and his Critique of Practical Reason in 1788. These two works had quickly fired the enthusiasm of the moral and religious humanists of the age. They wholeheartedly agreed with the central teaching of these works concerning man's moral freedom. Kant justified their faith that man was free to raise himself above nature to spiritual self-realization, and that in order to do so he required the help of neither nature below nor God above. The religion of these men was a humanistic religion, whose essential faith was in man's inherent goodness. If they thought of evil at all, they understood it as mere inertia, to be progressively removed by man himself. They rejected a religion which regarded evil in man as somehow essential. Thus if they were Christians, they were Christians of a very unorthodox sort. For they repudiated original sin, and the incarnation required to wipe it out.

Among the admirers of Kant were the great German poets. Schiller regarded the Kantian “determine thyself” as one of the greatest words ever spoken by man. Goethe, though less favorably inclined toward Kant, was nevertheless able to write under his influence the telling sentence: “God is the objectivation of the feeling of human dignity.” The great German poets regarded Kant as an ally in their battle for the dignity of man.

And now Kant suddenly spoke of radical evil! Moreover, he treated it as if it were an essential part of religion! He seemed to have turned traitor to his own gospel of man's moral freedom, and to have gone over to the enemy, to the detractors of man. True, Kant had spoken of evil before. But he had not spoken of radical evil. Evil had been merely the “incomplete development of the capacity for good.”