The third formulation of the CI is “the idea of the will of every rational being as a will that legally establishes universal law.” (G 4-432). Although Kant does not state it as an imperative, as he does in other formulations, it is quite easy to formulate it in this form: Act in such a way that you can be a legislator of universal laws through your maxims. It sounds a lot like the first wording. In this case, however, we focus on our status as universal legislators rather than supporters of universal laws. This, of course, is the source of the dignity of humanity that Kant speaks of in the second formulation. A rational will, bound only by universal laws, could act accordingly for natural, not moral, motives such as self-interest. But to be a legislator of universal laws, such contingent motives, motives that rational actors like us may or may not have, must be set aside. Therefore, according to this formulation, we are obliged to adapt our behavior to the principles that express this autonomy of rational will – its status as the source of the very universal laws that bind it. As with the formula of humanity, this new formulation of the CI does not change the result, since everyone should formulate the same moral law and, in a sense, “unite” the other formulations in it. Kant takes each formulation that the first succeeds in his own way as the moral law “closest to feeling.” The formula of autonomy presumably does so by exhibiting the source of our dignity and worth, our status as free rational agents who are the source of authority behind the moral laws that bind us. Some interpreters of Kant, notably Korsgaard (1996), seem to assert a kind of quietism on metaethics by rejecting many of the assumptions on which contemporary metaethical debates are based.
For example, some of these philosophers do not seem to want to claim that facts and moral qualities are merely the result of deliberative procedures. Rather, they seem more willing to dismiss talking about facts and characteristics as unnecessary once a perfectly acceptable and defensible consultation procedure is in place. That is, the whole framework of facts and characteristics suggests that there is something we need to anchor our moral ideas “out there” in reality, when in reality we only need one way to decide. Once we become more sensitive to the ethical concerns that really matter to us as rational actors, we will find that many of the issues that animate metaethicists turn out to be non-questions or of little importance. Others, however, have expressed doubts as to whether Kantians can so easily avoid engaging in metaethical debates (Hussain & Shaw 2013). Kant`s moral theory connects in some ways with the rest of his philosophy, but differs mainly from it. Kant took Hume`s critique of epistemology seriously, but rejected Hume`s claim that morality is based on feeling. For Kant, everything revolves around reason.
Let us suppose, for the sake of argument, that we agree with Kant. We must now know what distinguishes the principle that defines our duties from these other motivating principles, thus making motivation the source of unfettered values. According to Kant, the categorical imperative is an objective, unconditional and necessary principle of reason that applies to all rational actors in all circumstances. Although Kant cites several examples illustrating this principle in Groundwork, in later writings, notably The Metaphysics of Morality, he describes a complicated normative ethical theory for interpreting and applying the CI to human persons in the natural world. Its framework includes different levels, distinctions and application procedures. In particular, Kant describes two secondary principles that aim to capture different aspects of CI. The universal principle of law, which governs questions of justice, rights and external actions that can be applied by force, states that “every action is just if it can coexist with the liberty of all in accordance with a universal law, or if, according to its maxim, the freedom of choice of each can coexist with the freedom of each in accordance with a universal law” (MM 6, 230).