The Categorical Imperative

Act only as you would want everyone to act. Kant argued this single principle is the foundation of all morality, derived from reason alone.

Kant wanted to put ethics on the same footing as mathematics: certain, universal, derived from reason rather than custom or feeling. His answer was the categorical imperative: act only according to a maxim you could will to become a universal law. A second formulation says the same thing differently: treat every person always as an end, never merely as a means. These are not two rules but one, seen from different angles. The imperative is categorical because it applies unconditionally, not just when it is convenient. Kant believed this was the first time morality had been given a proper foundation.