# 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:

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Contributed by: Izidor Hafner (April 2016)

Open content licensed under CC BY-NC-SA

## Snapshots

## Details

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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