A rule of inference in propositional logic. Written as 'Taut' for short.

P = (P∨P)
And
P = (P∧P)

Basically, 'there is an apple' is the same as 'there is an apple and an apple' and the same as 'there is an apple or an apple'. This is most often used in reverse, so that if you manage to prove (P ∧ P) you can state that you have proved P. Logicians like to be very, very, very precise.


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