Combining Philosophers

Ideas for Hermarchus, Jos L. Zalabardo and Christopher Peacocke

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2 ideas

5. Theory of Logic / B. Logical Consequence / 4. Semantic Consequence |=
Γ |= φ for sentences if φ is true when all of Γ is true [Zalabardo]
     Full Idea: A propositional logic sentence is a 'logical consequence' of a set of sentences (written Γ |= φ) if for every admissible truth-assignment all the sentences in the set Γ are true, then φ is true.
     From: José L. Zalabardo (Introduction to the Theory of Logic [2000], §2.4)
     A reaction: The definition is similar for predicate logic.
Γ |= φ if φ is true when all of Γ is true, for all structures and interpretations [Zalabardo]
     Full Idea: A formula is the 'logical consequence' of a set of formulas (Γ |= φ) if for every structure in the language and every variable interpretation of the structure, if all the formulas within the set are true and the formula itself is true.
     From: José L. Zalabardo (Introduction to the Theory of Logic [2000], §3.5)