Autonomy of the Will

All previous moral theories, Kant argues, were guilty of heteronomy: they grounded morality in something external to the will — pleasure, divine command, social approval, or natural instinct. Such theories can never yield genuine moral obligation, because a principle derived from outside the will is merely a counsel of prudence or custom, not an unconditional command.

A truly autonomous will does not merely follow rules imposed upon it; it recognises the moral law as a principle it gives to itself as a rational being. When I act morally, I am not obeying an alien authority — I am expressing my rational nature in its purest form. The moral law is not a constraint on freedom but its fullest expression.

Autonomy is the basis of human dignity. Because rational beings are self-legislators, they possess a worth that cannot be assigned a price. The ideal moral community — the kingdom of ends — is the community of all autonomous rational beings who each legislate universally while respecting the self-legislation of every other. Treating persons as ends in themselves is, for Kant, simply recognising their status as autonomous agents.

Autonomy is introduced in the Groundwork and given its fullest systematic treatment in the Critique of Practical Reason, Analytic, Chapter III.