Immanuel Kant, Groundwork of the Metaphysics of Morals II

Posted: Wed, Oct 8, 2025

Translating Kant into contemporary normative ethical terms

Grounding deontic status in rational agency: X is the morally right/wrong thing to do because it satisfies/fails the principle of practical reason (i.e., the categorical imperative).

Formula of universal law: Kant has in mind practical reason that’s a priori and holds with absolute necessity, which implies the universality of its requirements; “I ought never to act except in such a way that I could also will that my maxim should become a universal law” (G 4:402).
The humanity formulation: Rational nature is not merely instrumentally valuable but “exists as an end in itself,” which implies that rational agents, insofar as we are rational, also exist as ends in ourselves; “act that you use humanity, whether in your own person or in the person of any other, always at the same time as an end, never merely as a means” (4:429).
The autonomy formulation: Our rational nature is such that we do not merely obey but legislate the categorical imperative; act that you regard “the will of every rational being as a will giving universal law” (4:431).
The kingdom of ends formulation: We end up with a picture where we are not only ends in ourselves individually, but “in systematic connection” forming “a kingdom of ends” (4:433); “every rational being must act as if he were by his maxims at all times a lawgiving member of the universal kingdom of ends” (4:438).

Are all of these formulations as equivalent as Kant thinks they are?

Getting our hands dirty

Apply both the universal law formulation and the humanity formulation to Kant’s four examples (G 4:421–23).

Suicide
False promise
Self-cultivation
Helping others