 By contrast, the Stoics defined negation (apophatikon) as an iterating external operator. For Alexander of Aphrodisias, “Not: not: it is day differs from it is day only in manner of speech” (Mates 1953, 126). With their propositional connectives and one-place truth/falsity-toggling negation operator, it is the Stoics rather the Aristotelians who prefigured modern propositional logic, as well as the precepts of traditional grammar (“Duplex negatio affirmat”) and the Law of Double  Negation.[5]