All attempts to prove rationally the existence of God through cosmological, teleological, historical and ontological evidence are, according to Kant, devoid of convincing. They all go beyond the possibilities of reason, and therefore, in the then sense of uncriticality, of dogmatic creation, ripped from experience rational speculation, metaphysics is no longer possible. However, this does not mean that metaphysics is impossible and unnecessary.
On the contrary, Kant himself expressly emphasizes that his critique seeks not to eliminate any metaphysics but to clear the path, to point to the methods of positive, critical metaphysics, since he believes that metaphysics is not only older than all other sciences, but also will remain forever, even when all other sciences have completely disappeared into the abyss of the all-consuming barbarism. The transformation of metaphysics into a positive science is possible by criticizing and establishing the cognitive abilities of human reason. Therefore, in 1781, Kant wrote to his friend and student Hertz about the importance of this book: "This type of research will always be difficult because it contains metaphysics for metaphysics. In the famous preface to the second edition, Kant summarizing his achievements and revealing his intentions, points out that criticizing the rational evidence of the immortality of the soul and of God's existence was not about denying either God or immortality, , that they can not be proved rationally. The main merit of this critique (the cognitive abilities of reason) is that all objections to morality and religion in the future philosophy will be eliminated through the Socratic method, ie by clearly demonstrating to opponents that their claims go beyond the field of the possibilities of reason. There has always been some metaphysics.
It will always exist, and along with this, self-criticism of pure reason will also be necessary. "Thus the roots of materialism, fatalism, atheism and immorality, dreaminess and superstition, which can be harmful to everyone in general, and finally - idealism and skepticism, which are more dangerous for science schools and "I was bound to limit knowledge (within the limits of reason) to give place to the faith, because the dogmatism of metaphysics, ie the aspiration to go forward, without criticism of pure reason, is the source of all unbelief that counteracts the pestilence la, - unbelief, which is always and strongly dogmatic. As is known, Kant himself in his other book, Critique of Practical Reason, justifies the existence of God, the freedom of will and the immortality of the soul, but not as evidenced by the theoretical logical reason, but as irrefutable postulates of practical reason - - especially moral duty and moral feeling. In other words, human reason, despite the awareness of its limitation, continued to work on the fundamental problems of being. In this respect are the metaphysics created by Kant - Metaphysics of Manners, Metaphysics of Nature and a Metaphysics of Religion under the title Religion within the limits of reason. In other words, Kant is one of the deepest and most prolific metaphysics. He is not the principle enemy of metaphysics, but merely denies the right and possibility of exhausting only the depths of existence available to the religion.
However, this is not the question of the positivism of Auguste Conte and his followers who disagree with one or another, whether it is dogmatic or critical, metaphysics, but they are all opponents of every metaphysics. Positivism, and later non-positivism, believe that everything outside of the scope of our positive / positive / experience is inaccessible to knowledge. Questions such as those about the beginning and meaning of the world, of the soul, of immortality, of freedom of will are not given in the experience and can not be the subject of scientific research. Only available to the senses objects and phenomena and their most immediate connection should be studied. Then our knowledge will be positive and practically useful. Mankind has come, according to positivism, gradually to this consciousness. Initially, it has spent a theological stage in which it has explained everything by the action of hidden living beings, spirits who have been worshiped and deified. Later this stage gave way to metaphysical. Here things were explained by the admission of some hidden, inaccessible for reason, complex mental speculations, and therefore knowledge lost its positive and beneficial character. Finally, through the work of Kant himself, this stage is overwhelmed and replaced by the era of positivism, "which will no longer end. Here, any metaphysics was impossible and completely redundant.