Completeness theorem, 4

Why truth table is not used in logic?

— JiminP

… the difference between semantics and syntax. A syntactic proof is a finite formal derivation of a sentence from the axioms of a theory using the logical axioms and the rules of inference of a logic. A proof by a truth table is a semantic proof; in allowing truth tables you are tacitly assuming the completeness theorem of propositional logic. Essentially, a priori, we don’t know that everything we can prove by studying the models of a theory (i.e. truth tables, in the case of propositional logic) can be proven syntactically, or even for that matter vice versa. It’s a non-trivial result in logic, …

— Zhen Lin

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— Mathematics – Stack Exchange

2012.09.27 Thursday ACHK