contrarius

Contrarius is a Latin adjective meaning opposite or opposing, derived from contra “against.” In English, the form is mostly encountered in historical or scholarly contexts, where contrarius and its plural contrarii are used to denote opposites or opposing relations. Modern usage more commonly relies on the related terms opposite, contrary, or contraries.

In philosophy and logic, contraries refer to a specific relation between universal propositions in Aristotelian and scholastic logic. Contraries are statements that cannot both be true, yet can both be false. A classic pair is “All S are P” and “No S are P.” This contrariety differs from contradiction, where one proposition must be true if the other is false. The concept appears in medieval logic and in discussions of the square of opposition, where contraries occupy the top corners, expressing a high level of opposition between universal affirmative and universal negative statements.

In music theory, contrarius appears in Latin sources to describe contrary motion, where two melodic lines move in opposite directions. While modern English music theory typically uses the term “contrary motion” rather than the Latin adjective, historical treatises and Latin tutors sometimes employ contrarius to characterize opposing melodic movement between voices.

Beyond these domains, contrarius chiefly survives in etymological references and in discussions of historical logic or music, serving as a reminder of the Latin roots that underpin many scholarly terms for opposition and contrast.