Maxim Tester
Take Kant's own examples step by step through the test of the categorical imperative.
Categorical imperative
The supreme principle of Kantian ethics: “act only in accordance with that maxim through which you can at the same time will that it become a universal law.”
The categorical imperative commands unconditionally — unlike hypothetical imperatives, which only say: “If you want X, do Y.” Kant states it in several equivalent formulas, including the universal-law formula and the humanity formula (“act so that you treat humanity … always at the same time as an end, never merely as a means”).
Testing a maxim proceeds in two stages: can it be conceived without contradiction as a universal law? If it already fails here — like the false promise — the action violates a strict, perfect duty. If it can be conceived but not willed without contradiction — like the maxim of never helping others in need — it violates a wider, imperfect duty.
Try it yourself
Your own maxim
Test a rule from your everyday life with Kant's questions — including the formula of humanity.
Dilemma workshop
Tricky cases based on Kant's own examples: decide for yourself first, then Kant speaks.
Flashcards
Review the concept with the Leitner flashcards — what you know comes back less often.
Where it appears
- Ethics — The categorical imperative
- Peace & Politics — Peace out of self-interest
- Timeline
- Works
- Anthropology from a Pragmatic Point of View — Structure & key ideas
- The Metaphysics of Morals — Origins & context
- Groundwork of the Metaphysics of Morals
- On a Supposed Right to Lie from Philanthropy — Impact & relevance today
- FAQ
- Home — Kant in five minutes
- Kant against Kant
- Doing