Critique of Practical Reason

In the Preface, Immanuel Kant declares his intent is to demonstrate the existence of what he calls “pure practical reason.” However, he also suggests that the term is redundant, as any use of reason that is practical, meaning it “proves its reality and that of its concepts by what it does”, is by definition pure. This is in contrast to abstract or “speculative” reason, which is not pure in of itself but can be pursued in a way that is pure, meaning detached from any experiential evidence. The differences between practical and speculative reason are shown in the case of freedom. Under speculative reason, one can question the existence of free will, a degree of skepticism that, in Kant’s view, would deprive life of all meaning. Through practical reason, however, freedom’s objective reality is shown through “the moral law.” In addition, Kant argues that the existence of free will is proven through a priori reasoning, by which he means that we intuitively know that free will exists. Similarly, the existence of abstract concepts of God and immortality is revealed to an individual’s will through