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:
“Just as soon as we notice that someone has to force himself to pay attention when dealing and talking with us, we have a valid demonstration that he does not love us or that he does not love us anymore.”
—Friedrich Nietzsche (1844–1900)
“Given for one instant an intelligence which could comprehend all the forces by which nature is animated and the respective positions of the beings which compose it, if moreover this intelligence were vast enough to submit these data to analysis, it would embrace in the same formula both the movements of the largest bodies in the universe and those of the lightest atom; to it nothing would be uncertain, and the future as the past would be present to its eyes.”
—Pierre Simon De Laplace (1749–1827)