Compatibilism is the belief that free will and determinism are compatible ideas, and that it is possible to believe in both without being logically inconsistent. Compatibilists believe freedom can be present or absent in situations for reasons that have nothing to do with metaphysics. They define free will as freedom to act according to one's motives without arbitrary hindrance from other individuals or institutions.
For example, courts of law make judgments, without bringing in metaphysics, about whether an individual was acting of their own free will in specific circumstances. It is assumed in a court of law that someone could have done otherwise than they did—otherwise no crime would have been committed.
Similarly, political liberty is a non-metaphysical concept. Statements of political liberty, such as the United States Bill of Rights, assume moral liberty, i.e. the ability to choose to do otherwise than one does.
Compatibilism was championed by the ancient stoics and medieval scholastics (such as Thomas Aquinas), and by Enlightenment philosophers (like David Hume and Thomas Hobbes). More specifically, the scholastics, including Thomas Aquinas, rejected what would now be called "compatibilism"—they held that humans could do otherwise than they do, otherwise the concept of sin is meaningless. As for the Jesuits, their concern was to reconcile the claim of God's foreknowledge of who would be saved with moral agency. The term itself was coined as late as the 20th century. Contemporary compatibilists range from the philosopher and cognitive scientist Daniel Dennett, particularly in his works Elbow Room (1984) and Freedom Evolves (2003), to the existentialist philosopher Frithjof Bergmann.