deontic modality

Deontic logic is a branch of modal logic that examines concepts of permission, obligation, and prohibition. These are known as deontic modalities, derived from the Greek word for "binding". Deontic logic aims to logically connect propositions related to these concepts. For example, it explores the idea that if an action is obligatory, then performing it must be permitted, and not performing it must be forbidden.1

This field was founded by G.H. von Wright in 1951 and uses operators like "O" for obligation and "P" for permission. These operators share similarities with necessity and possibility operators in modal logic. Deontic logic is distinct from substantive fields like ethics and law, which deal with the specific content of what is forbidden or permitted.21