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Ideas for '', 'Summula philosophiae naturalis' and 'Philosophical Logic'

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2 ideas

5. Theory of Logic / I. Semantics of Logic / 3. Logical Truth

15408	'Tautologies' are valid formulas of classical sentential logic - or substitution instances in other logics [Burgess]
	Full Idea: The valid formulas of classical sentential logic are called 'tautologically valid', or simply 'tautologies'; with other logics 'tautologies' are formulas that are substitution instances of valid formulas of classical sentential logic.
	From: John P. Burgess (Philosophical Logic [2009], 1.5)

5. Theory of Logic / I. Semantics of Logic / 4. Satisfaction

15418	Validity (for truth) and demonstrability (for proof) have correlates in satisfiability and consistency [Burgess]
	Full Idea: Validity (truth by virtue of logical form alone) and demonstrability (provability by virtue of logical form alone) have correlative notions of logical possibility, 'satisfiability' and 'consistency', which come apart in some logics.
	From: John P. Burgess (Philosophical Logic [2009], 3.3)