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:
“It is not enough that France should be regarded as a country which enjoys the remains of a freedom acquired long ago. If she is still to count in the world—and if she does not intend to, she may as well perish—she must be seen by her own citizens and by all men as an ever-flowing source of liberty. There must not be a single genuine lover of freedom in the whole world who can have a valid reason for hating France.”
—Simone Weil (1909–1943)
“Every formula which expresses a law of nature is a hymn of praise to God.”
—Maria Mitchell (1818–1889)