Formal Notation
The biconditional introduction rule may be written in sequent notation:
where is a metalogical symbol meaning that is a syntactic consequence when and are both in a proof;
or as the statement of a truth-functional tautology or theorem of propositional logic:
where, and are propositions expressed in some formal system.
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Famous quotes containing the word formal:
“It is in the nature of allegory, as opposed to symbolism, to beg the question of absolute reality. The allegorist avails himself of a formal correspondence between “ideas” and “things,” both of which he assumes as given; he need not inquire whether either sphere is “real” or whether, in the final analysis, reality consists in their interaction.”
—Charles, Jr. Feidelson, U.S. educator, critic. Symbolism and American Literature, ch. 1, University of Chicago Press (1953)