discussion of Kant's Antinomies of Reason
excerpted from From Socrates to Sartre by Thelma Z. Lavine

The Antinomies and the Limits of Reason    Because regulative ideas do not refer to any objective reality about which we can have knowledge, we must consider these ideas as being the product of our pure reason. As such we cannot bring to these ideas the a priori forms of time and space or the category of cause and effect since these are imposed by us only upon the sensible manifold. Science is possible because all men, having the same structure of mind, will always and everywhere order the events of sense experience the same way; that is, we all bring to the given of sense experience the same organizing faculties of understanding. But there can be no science of metaphysics because there is not the same kind of given when we consider the ideas of self, cosmos, and God as when we consider "the shortest distance between two points." What is given in metaphysics is the felt need to achieve a synthesis of the wide variety of events in experience at ever-higher levels and of discovering an ever-wider explanation of the realm of phenomena.

There is a difference for Kant between a priori or theoretical scientific knowledge, on the one hand, and speculative metaphysics on the other. The difference is that we can have scientific knowledge of phenomena but cannot have scientific knowledge of the noumenal realm, or the realm that transcends experience. Our attempts to achieve a "science" of metaphysics, says Kant, are doomed to failure. Whenever we try to discuss the self, the cosmos, or God as though they were objects of experience, the inability of the mind ever to do so successfully is indicated by what Kant calls the antinomies into which we fall. These four antinomies show us that when we discuss the nature of the world beyond experience, we can argue with equal force on opposite sides of various propositions, namely, that (1) the world is limited in time and space, or that it is unlimited; that (2) every composite substance in the world is made up of simple parts, or that no composite thing in the world is made up of simple parts since there nowhere exists in the world anything simple; that (3) besides causality in accordance with the laws of nature there is also another causality, that of freedom, or that there is no freedom since everything in the world takes place solely in accordance with the laws of nature; and, finally, that (4) there exists an absolutely necessary being as a part of the world or as its cause, or an absolutely necessary being nowhere exists.

These antinomies reflect the disagreements generated by dogmatic metaphysics, disagreements that occur only because they are based upon "non-sense," that is, upon attempts to describe a reality about which we have, and can have, no sense experience.