1. A logical operation in which a proposition is converted by negating both the subject and predicate while keeping the same quality (affirmative or negative).
Usage: formal logic; technical term
2. The act of turning or facing in a different direction; a turning toward or away.
Usage: rare; archaic

Examples

• In formal logic, the obversion of 'All cats are animals' is 'No cats are non-animals.'
• The obversion of a negative proposition yields an affirmative one with negated terms.
• Students of logic learn obversion as one of the fundamental operations on categorical propositions.
• The obversion rule is useful for transforming statements while preserving logical equivalence.