Published online by Cambridge University Press: 06 August 2010
At the very heart of the argument of the Critique of Practical Reason, one finds Kant's puzzling discussion of the ‘fact of reason’. Kant introduces the notion in the course of arguing that pure reason is practical, which is the main task of the first chapter of the Analytic. Having claimed that ‘we’ have a ‘consciousness of the moral law’, and that this leads us to the concept of the freedom of the will (CpV 5:29–30), Kant argues that the consciousness of the moral law can be called a ‘fact of reason’. This passage is found in the brief remark between the two most important conclusions of the second Critique. It is located between the formulation of the ‘Fundamental Law of Pure Practical Reason’, ‘so act that the maxim of your will could always hold at the same time as a principle in a giving of universal law’ (CpV 5:30), and the ‘Conclusion’ that ‘Pure reason is practical of itself alone and provides (the human being) with a universal law which we call the moral law’ (CpV 5:31). Even if the exact role of the notion of a ‘fact of reason’ is not immediately clear, there is no doubt that the argument in which it plays a role is central to Kant's moral theory.
Ever since it saw the light of day, however, Kant's argument regarding the fact of reason has met with strong criticism, although the critics disagree fundamentally as to what exactly is wrong with it.