The subject of possibility is a central topic in philosophy. It was frequently discussed in the history of philosophy, and it is actively debated by contemporary philosophers.

Historical Developments

Aristotle

The first comprehensive treatment of possibility occurs in the work of Aristotle. Aristotle's writing on this subject is difficult and confusing, but he seems to have held that the idea of possibility is derivative from that of necessity and negation, "It is possible that P" meaning "It is not necessary that not-P" (see On Interpretation 13.22b). Necessity of this basic kind is absolute necessity, and like absolute possibility it is applicable to sentences or propositions (logoi). According to his Posterior Analytics (4.21), a necessary proposition truly predicates something of a thing's essence; an example would be "A man is a rational being." A possible proposition, one that may be asserted to be such by a proposition containing the words...