obversion a sort of immediate inference that allows a transformation of affirmative categorical A-propositions and I-propositions into the corresponding negative E-propositions and O-propositions, and of E- and O-propositions into the corresponding A- and I-propositions, keeping in each case the order of the subject and predicate terms, but changing the original predicate into its complement, i.e., into a negated term. For example, ‘Every man is mortal’ – ‘No man is non-mortal’; ‘Some students are happy’ – ‘Some students are not non-happy’; ‘No dogs are jealous’ – ‘All dogs are non-jealous’; and ‘Some bankers are not rich’ – ‘Some bankers are not non-rich’. See also SQUARE OF OPPOSITION , SYLLOGIS. I.Bo.