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.[1] As Steven Weinberg puts it: "I would say that free will is nothing but our conscious experience of deciding what to do, which I know I am experiencing as I write this review, and this experience is not invalidated by the reflection that physical laws made it inevitable that I would want to make these decisions."[2] The opposing belief, that the thesis of determinism is logically incompatible with the classical thesis of free will, is known as "incompatibilism".
Compatibilists believe that freedom can be present or absent in situations for reasons that have nothing to do with metaphysics.[3] In other words, that causal determinism does not exclude the truth of possible future outcomes.[4] 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.[5] 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.[6]