Categorical Imperative: The supreme principle of morality, according to Immanuel Kant. Kant distinguished between a hypothetical imperative, which commands an action conditionally as a means to an end that does not necessarily have to be willed (such as "Brush your teeth regularly if you want to avoid having cavities"), and a categorical imperative, which commands an actions absolutely. Kant believed that there is only one categorical imperative: to act only on the basis of maxims that can be universally willed as rational law. He thought that this one imperative could be formulated in several different ways, including the famous formula of the end in itself, in which we are enjoined to act in such a manner that we always recognize that rational agents have intrinsic worth and dignity and are not to be treated merely as a means to our own ends.1
1. C.Stephen Evans, Pocket Dictionary of Apologetics & Philosophy of Religion (Downers Grove, IL: InterVarsity Press, 2002), pp. 21.