Some articles on logically valid:
... The completeness theorem says that if a formula is logically valid then there is a finite deduction (a formal proof) of the formula ... rules are required to prove all the logically valid formulas ... A converse to completeness is soundness, the fact that only logically valid formulas are provable in the deductive system ...
... A first-order formula is called logically valid if it is true in every structure for the language of the formula ... A deductive system is called complete if every logically valid formula is the conclusion of some formal deduction, and the completeness theorem for a particular deductive system is the theorem ... A converse to completeness is soundness, the fact that only logically valid formulas are provable in the deductive system ...
Famous quotes containing the words valid and/or logically:
“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 worldand if she does not intend to, she may as well perishshe 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 (19091943)
“The concept of a person is logically prior to that of an individual consciousness. The concept of a person is not to be analysed as that of an animated body or an embodied anima.”
—Sir Peter Frederick Strawson (b. 1919)