Editing Propositional calculus (section)

== History ==
{{main|History of logic}}
Although propositional logic (also called propositional calculus) had been hinted by earlier philosophers, it was developed into a formal logic ([[Stoic logic]]) by [[Chrysippus]] in the 3rd century BC<ref name="ms1"/> and expanded by his successor [[Stoics]]. The logic was focused on [[proposition]]s. This was different from the traditional [[syllogism|syllogistic logic]], which focused on [[Syllogisms#Terms in syllogism|terms]]. However, most of the original writings were lost<ref name="ms2"/> and, at some time between the 3rd and 6th century CE, Stoic logic faded into oblivion, to be resurrected only in the 20th century, in the wake of the (re)-discovery of propositional logic.<ref name="ms3"/>

[[Symbolic logic]], which would come to be important to refine propositional logic, was first developed by the 17th/18th-century mathematician [[Gottfried Leibniz]], whose [[calculus ratiocinator]] was, however, unknown to the larger logical community. Consequently, many of the advances achieved by Leibniz were recreated by logicians like [[George Boole]] and [[Augustus De Morgan]], completely independent of Leibniz.<ref name="ms4"/>

[[Gottlob Frege|Gottlob Frege's]] [[predicate logic]] builds upon propositional logic, and has been described as combining "the distinctive features of syllogistic logic and propositional logic."<ref name="ms5"/> Consequently, predicate logic ushered in a new era in logic's history; however, advances in propositional logic were still made after Frege, including [[natural deduction]], [[Method of analytic tableaux|truth trees]] and [[truth-table|truth tables]]. Natural deduction was invented by [[Gerhard Gentzen]] and [[Stanisław Jaśkowski]]. Truth trees were invented by [[Evert Willem Beth]].<ref name="ms6"/> The invention of truth tables, however, is of uncertain attribution.

Within works by Frege<ref name="Truth in Frege"/> and [[Bertrand Russell]],<ref name="Russell Truth-Tables"/> are ideas influential to the invention of truth tables. The actual tabular structure (being formatted as a table), itself, is generally credited to either [[Ludwig Wittgenstein]] or [[Emil Post]] (or both, independently).<ref name="Truth in Frege" /> Besides Frege and Russell, others credited with having ideas preceding truth tables include Philo, Boole, [[Charles Sanders Peirce]],<ref name="ms7"/> and [[Ernst Schröder (mathematician)|Ernst Schröder]]. Others credited with the tabular structure include [[Jan Łukasiewicz]], [[Alfred North Whitehead]], [[William Stanley Jevons]], [[John Venn]], and [[Clarence Irving Lewis]].<ref name="Russell Truth-Tables" /> Ultimately, some have concluded, like John Shosky, that "It is far from clear that any one person should be given the title of 'inventor' of truth-tables".<ref name="Russell Truth-Tables" />