Compatibilism is the belief that free will and determinism are mutually compatible and that it is possible to believe in both without being logically inconsistent.
Compatibilists believe that freedom can be present or absent in situations for reasons that have nothing to do with metaphysics. In other words, that causal determinism does not exclude the truth of possible future outcomes. Because free will is seen as a necessary prerequisite for moral responsibility, compatibilism is often used to support compatibility between moral responsibility and determinism.
Similarly, political liberty is a non-metaphysical concept. Statements of political liberty, such as the United States Bill of Rights, assume moral liberty: the ability to choose to do otherwise than what one does.
Compatibilism was mentioned and championed by the ancient Stoics and some medieval scholastics. More specifically, scholastics like Thomas Aquinas and later Thomists (such as Domingo Báñez) are often interpreted as holding that human action can be free, even though an agent in some strong sense could not do otherwise than what they did. Whereas Aquinas is often interpreted to maintain rational compatibilism (i.e., an action can be determined by rational cognition and yet free), later Thomists, such as Báñez, develop a sophisticated theory of theological determinism, according to which actions of free agents, despite being free, are, on a higher level, determined by infallible divine decrees manifested in the form of "physical premotion" (praemotio physica), a deterministic intervention of God into the will of a free agent required to reduce the will from potency to act. A strong incompatibilist view of freedom was, on the other hand, developed in the Franciscan tradition, especially by Duns Scotus, and later upheld and further developed by Jesuits, especially Luis de Molina and Francisco Suárez. In the early modern era, compatibilism was maintained by Enlightenment philosophers (such as David Hume and Thomas Hobbes).