....Immanuel Kant's (1724-1804) contemporaries among the German philosophers held to the orthodox point of view. They rejected materialism as godless and immoral. Kant, however, was not satisfied with such a simple solution. He knew full well the flimsiness of the traditional religious notions. But he had neither enough courage nor enough consistency definitely to break with the old.
In 1781 he published his magnum opus the Critique of Pure Reason in which he established most conclusively that all knowledge was empirical, and that there were no proofs for the existence of a God, the immortality of the soul, absolute ideas, etc. We do not know things in themselves, their essences. We can know only the forms in which these essences manifest themselves to our sensory organs. The essence of things (noumenon) is concealed behind the form (phenomenon) and it will forever remain in the realm of the unknown. It appeared that the gulf between materialism and idealism, between science and religion was bridged. Kant did not deny the successes of science in the study and the explanation of phenomena. But he also found a place for theology. The essence was christened with the name of God.
In his double-entry system of bookkeeping, in his determination to offend neither science nor religion, Kant went even further. In his next work, the Critique of Practical Reason, he proceeded to prove that though in theory the conceptions God, immortality of the soul, etc., are not indispensable, in practice one is forced to accept them, for without them human activity would be devoid of any moral basis.
The poet Heine, who was a friend of Marx and upon whom the latter at one time had a great influence, depicted very vividly Kant's motives for treading the two paths. Kant had an old and faithful servant, Lampe, who had lived with, and attended to, his master for forty years. For Kant this Lampe was the personification of the average man who could not live without religion. After a brilliant exposition of the revolutionary import of the Critique of Pure Reason in the struggle with theology and with the belief in a Divine Principle, Heine explained why Kant found it necessary to write the Critique of Practical Reason in which the philosopher re-established everything he had torn down before. Here is what Heine wrote:
"After the tragedy comes the farce. Immanuel Kant has hitherto appeared as the grim, inexorable philosopher; he has stormed heaven, put all the garrison to the sword; the ruler of the world swims senseless in his blood; there is no more any mercy, or fatherly goodness, or future reward for present privations; the immortality of the soul is in its last agonies -- death rattles and groans. And old Lampe stands by with his umbrella under his arm as a sorrowing spectator, and the sweat of anguish and tears run down his cheeks. Then Immanuel Kant is moved to pity, and shows himself not only a great philosopher, but a good man. He reconsiders, and half good-naturedly and half ironically says, 'Old Lampe must have a God, or else the poor man cannot be happy, and people really ought to be happy in this world. Practical common sense declares that. Well, meinet wegen, for all I care, let practical reason guarantee the existence of a God.'" [Heinrich Heine, Collected Works. W. Heineman, London, 1906. Vol. 5, pp. 150-151.]Kant had a great influence on science, too. Together with the French astronomer Pierre Laplace (1749-1827), he maintained that the biblical account of the creation of the world was faulty, that the earth was the product of a prolonged development, of a continuous evolutionary process, that like all heavenly bodies it came about as the gradual congealment of a highly rarefied substance.
Kant was essentially a mediator between the old and the new philosophies; he remained a compromiser in most practical fields of life. Though he was not able completely to break away from the old, he none the less made a considerable step forward. His more consistent disciples rejected the Critique of Practical Reason and made the most extreme deductions from his Critique of Pure Reason.