One key differentiation that needs to be made is the difference between Hypothetical and Categorical Imperatives. Whilst Hypothetical imperatives are based on ‘you must do x to achieve y’ (you must exercise to keep fit), the Categorical imperative is based on ‘you must do x’ or alternatively ‘you must not do x’ (you must never lie).

Some basic points on the Categorical Imperative:

  • Applies to everyone.
  • The ‘supreme principle of morality’.
  • Depends on nothing else (e.g. desires or inclinations).
  • Moral imperatives are categorical (you must do x).
  • ‘a priori’ – derived through reason.

Kant’s Categorical imperative is split into 3 main Formula’s for deciding whether or not an act is moral.


  1. The Formula of the Universal Law of Nature: Also known as the Universal Law – ‘Act only according to that maxim by which you can at the same time will that it shall become a universal law.’ – Meaning that an act is only moral if it would be acceptable for everyone to do it (e.g. lying would be morally wrong as if everyone lied, there would be no truth).
  2. The Formula of End in itself: Also known as the Humanity Law – ‘Act so as to treat people always as ends in themselves, never as mere means.’ – Meaning that we should never simply use people as a way of reaching our duty.
  3. The Formula of Kingdom of Ends: “Act in accordance with the maxims of a member giving universal laws for a merely possible kingdom of ends” – Meaning we conform our actions to the laws of an ideal moral world, and these actions must have ful acceptance by a community of fully rational agents.