Definitions of Two-Placed Connectives in Lesniewski's Protothetic

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To describe his extended propositional calculus (protothetic), which is a logical system based on a single axiom, Leśniewski invented a special notation for a propositional function of two arguments . He used a circle and up to four lines around the circle, which point to those values of arguments of
for which the function is true, according to the diagram:
Contributed by: Izidor Hafner (April 2016)
Open content licensed under CC BY-NC-SA
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The names of the propositional functions are taken from [1, pp. 19–20]. Disjunction and alternation are reversed with respect to modern usage. The protothetic axiom from 1926 was copied from [2, pp. 129].
References
[1] J. J. T. Srzednicki and Z. Stachniak, eds., S. Leśniewski's Lecture Notes in Logic, New York: Springer, 1988.
[2] S. McCall, ed., Polish Logic, 1920–1939, Oxford: Oxford University Press, 1967.
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