A hypothetical imperative says: if you want X, do Y. A categorical imperative commands unconditionally. Immanuel Kant gives several formulations in the Groundwork of the Metaphysics of Morals (1785):
- Universal law — “Act only according to that maxim whereby you can at the same time will that it should become a universal law.”
- Humanity — “Act in such a way that you treat humanity, whether in your own person or in the person of any other, never merely as a means to an end, but always at the same time as an end.”
- Autonomy / Kingdom of Ends — act as a legislating member of a kingdom of ends.
The famous test: may I make a false promise to get money? Universalize it — everyone lies when convenient — and promising itself collapses. The maxim contradicts itself.
The famous objection: Benjamin Constant asked whether you may lie to a murderer at the door asking where your friend is hiding. Kant answered (1797) — no. Critics from Hegel (“empty formalism”) to Friedrich Nietzsche (“the categorical imperative smells of cruelty”) have attacked it ever since.
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related by shared connectionsThe Enlightenment
The eighteenth-century movement that put reason, science, tolerance and individual liberty at the centre of human affairs — “Sapere aude!”
Jean-Jacques Rousseau
The Genevan philosopher of nature, freedom and feeling — “Man is born free, and everywhere he is in chains” — whose Social Contract inspired revolutionaries and whose Confessions invented modern autobiography.
Critique of Practical Reason
Kant’s second Critique — the moral law is a fact of reason, and through it we know we are free.
Rationalism vs. Empiricism
The great quarrel of early modern philosophy — does knowledge come from reason or from experience? Kant tried to end it.
British Empiricism
The view that all knowledge comes from experience — the mind begins as a blank slate on which the senses write.
German Idealism
The extraordinary philosophical movement after Kant — Fichte, Schelling, Hegel — that tried to complete his revolution by showing reality itself to be the work of mind or Spirit.