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Ideas for 'fragments/reports', 'Elucidation of some points in E.Schrder' and 'The Principles of Mathematics'

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2 ideas

5. Theory of Logic / B. Logical Consequence / 8. Material Implication

14108	It would be circular to use 'if' and 'then' to define material implication [Russell]
	Full Idea: It would be a vicious circle to define material implication as meaning that if one proposition is true, then another is true, for 'if' and 'then' already involve implication.
	From: Bertrand Russell (The Principles of Mathematics [1903], §037)
	A reaction: Hence the preference for defining it by the truth table, or as 'not-p or q'.

14106	Implication cannot be defined [Russell]
	Full Idea: A definition of implication is quite impossible.
	From: Bertrand Russell (The Principles of Mathematics [1903], §016)