KANT'S GRAND PROJECT

Kant's project in the third section of the Groundwork is exhilaratingly bold. He seeks to obtain, from the idea of acting freely – which (we shall see) is the same as the idea of acting from reasons – a principle governing how rational beings should act. It consists in a requirement of impartiality of a particular kind. We human beings, Kant thinks, in virtue of our sensuous nature, experience this principle as a ‘categorical imperative’, a constraint to be obeyed whatever our inclinations and actual aims may be. However, the principle as such applies to all reason-responsive beings – as it must, given that it is derived from the mere idea of acting for a reason.

Kant gives a number of formulations of the principle, holding them to be equivalent. From these, he has already argued in the two previous sections, we can obtain the imperatives of morality. In fact, he believes his principle gives us all and only the universal principles of morality which govern the behaviour of all reason-responsive beings; it is, he claims, morality's ‘supreme principle’ (G IV 392), hence, the categorical imperative.

Thus, the argument has two steps: from acting for a reason to the categorical imperative, and from that to morality. Taken together in their full strength, the two steps would produce a truly extraordinary result: any being capable of acting for reasons is bound by principles whose content can be deduced from that very idea.