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:
“The manifestation of poetry in external life is formal perfection. True sentiment grows within, and art must represent internal phenomena externally.”
—Franz Grillparzer (1791–1872)