In Immanuel Kant 's moral philosophy, an imperative that presents an action as unconditionally necessary (e.g., "Thou shalt not kill"), as opposed to an imperative that presents an action as necessary only on condition that the agent wills something else (e.g., "Pay your debts on time, if you want to be able to obtain a mortgage").
Kant held that there was only one formally categorical imperative, from which all specific moral imperatives could be derived. In one famous formulation, it is: "Act only according to that maxim by which you can at the same time will that it should become a universal law." See also deontological ethics .