Published online by Cambridge University Press: 06 August 2010
One aim of the Critique of Practical Reason is to establish that reason alone can determine the will. To show that it can, it suffices to show that there are practical principles given by reason alone – what Kant terms ‘practical laws’, or (roughly) requirements of reason on action. Chapter I of the Analytic accomplishes this aim by arguing that the moral law is an authoritative practical principle given as a ‘fact of reason’. The chapter begins in section 1 with a ‘Definition’ (Erklärung) of a practical law as a practical principle that holds necessarily for every rational being (as a principle that ‘determines the will simply as will’ without presupposing any subjective or rationally contingent interests). From this definition Kant uses conceptual arguments to derive three ‘Theorems’ and various ‘Corollaries’ that state conditions that any practical law must satisfy. The principal condition, stated in Theorem III, is that a practical law determines choice through its form – through ‘the mere form of giving universal law’ – rather than through its matter (CpV 5:27). The arguments culminate in section 7 with the statement of the ‘Fundamental Law of Pure Practical Reason’, which Kant identifies with the moral law: ‘So act that the maxim of your will could at the same time always hold as a principle in a giving of universal law’ (CpV 5:30).