ABSTRACT
A discussion of the syllogistic rule obversion, referred to by Ammonius as the canons of Proclus, in the context of Proclus’ version of the syllogistic. Assuming the semantic structure of Prolucs’ linear causal hirerarchy, it is argued that the rule is invalid if negation is interpreted as Boolean, but valid, with certain restrictions, if negation is interpreted as Neoplatonic privative or hypernegation.
