Immanuel Kant (1724–1804) introduced the term "categorical imperative" to characterize the fundamental principle of morality as it presents itself to beings. The principle is categorical, or unconditional, because it is valid for all humans, indeed, for all rational beings, independently of any particular desires or aims they may have. It presents itself as an imperative precisely because human beings have desires and aims that can be incompatible with the unconditional demands of the principle of morality and thus those demands often present themselves as obligations and constraints. Hence the propositional content of the fundamental principle of morality is identical for all rational beings, but its coloration as an imperative is distinctively human. For Kant, since there is a single fundamental principle of morality, there is, properly speaking, only a single categorical imperative, although more specific moral duties and obligations derivable from it are themselves unconditionally valid for...