Valid Formula
A formula of a formal language is a valid formula if and only if it is true under every possible interpretation of the language. In propositional logic, they are tautologies.
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Famous quotes containing the words valid and/or formula:
“Written poetry is worth reading once, and then should be destroyed. Let the dead poets make way for others. Then we might even come to see that it is our veneration for what has already been created, however beautiful and valid it may be, that petrifies us.”
—Antonin Artaud (1896–1948)
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—Lafcadio Hearn (1850–1904)