Editing William of Ockham (section)

===Logic===
In [[logic]], William of Ockham wrote down in words the formulae that would later be called [[De Morgan's laws]],<ref>In his ''Summa Logicae'', part II, sections 32 and 33.Translated on p. 80 of ''Philosophical Writings'', tr. [[Philotheus Boehner|P. Boehner]], rev. S. Brown, (Indianapolis, Indiana, 1990)</ref> and he pondered [[three-valued logic|ternary logic]], that is, a [[logical system]] with three [[truth values]]; a concept that would be taken up again in the [[mathematical logic]] of the 19th and 20th centuries. His contributions to [[semantics]], especially to the maturing [[theory of supposition]], are still studied by logicians.<ref>{{cite journal |first1=Graham |last1=Priest |author-link1=Graham Priest |last2=Read |first2=S. |title=The Formalization of Ockham's Theory of Supposition |journal=Mind |volume=LXXXVI |pages=109–113 |year=1977 |doi=10.1093/mind/LXXXVI.341.109 |issue=341}}</ref><ref>{{cite journal |author-link1=John Corcoran (logician) |first1=John |last1=Corcoran |first2=John |last2=Swiniarski |year=1978 |title=Logical Structures of Ockham's Theory of Supposition |journal=Franciscan Studies |volume=38 |pages=161–183 |jstor=41975391 |doi=10.1353/frc.1978.0010 |s2cid=170450442}}</ref> William of Ockham was probably the first logician to treat empty terms in Aristotelian syllogistic effectively; he devised an empty term semantics that exactly fit the syllogistic. Specifically, an argument is valid according to William's semantics if and only if it is valid according to ''Prior Analytics''.<ref>John Corcoran (1981). "Ockham's Syllogistic Semantics", ''Journal of Symbolic Logic'', '''46''': 197–198.</ref>