Tetralemma

The tetralemma is a figure that features prominently in the logic of India.

Definition

It states that with reference to any a logical proposition X, there are four possibilities:

${\displaystyle X}$ (affirmation)

${\displaystyle \neg X}$ (negation)

${\displaystyle X\land \neg X}$ (both)

${\displaystyle \neg (X\lor \neg X)\iff X\land \neg X\iff \emptyset }$ (neither)

Catuskoti

The history of fourfold negation, the Catuskoti (Sanskrit), is evident in the logico-epistemological tradition of India, given the categorical nomenclature Indian logic in Western discourse. Subsumed within the auspice of Indian logic, 'Buddhist logic' has been particularly focused in its employment of the fourfold negation, as evidenced by the traditions of Nagarjuna and the Madhyamaka, particularly the school of Madhyamaka given the retroactive nomenclature of Prasangika by the Tibetan Buddhist logico-epistemological tradition.

A variant of the tetralemma is used in the Ancient Greek philosophical schools of Democritus[1] and Pyrrhonism. Pyrrho includes it in his summary of his teachings, and Sextus Empiricus includes it among the Pyrrhonist Maxims.[2]

See also

• De Morgan's laws
• Paraconsistent logic
• Prasangika
• Two-truths doctrine
• Catuṣkoṭi, a similar concept in Indian philosophy
• Similarities between Pyrrhonism and Buddhism

References

1. Democritus: 5. Theory of Knowledge
2. Sextus Empiricus, Outlines of Pyrrhonism Book 1, Section 19

External links

• Wiktionary definition of tetralemma
• Twelve links blog Notes on the tetralemma