C onsequence Definition Let 2 be a(possibly infinite)set of propositions. We say that o is a consequence of 2(and write as 2h o) if, for any valuation v (D()= T for allT∈∑)→()=TConsequence Definition Let Σ be a (possibly infinite) set of propositions. We say that σ is a consequence of Σ (and write as Σ |= σ) if, for any valuation V, (V(τ ) = T for all τ ∈ Σ) ⇒ V(σ) = T. Yi Li (Fudan University) Discrete Mathematics April 24, 2012 4 / 25