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8375 | 'Necessary' is a predicate of a propositional function, saying it is true for all values of its argument [Russell] |
Full Idea: 'Necessary' is a predicate of a propositional function, meaning that it is true for all possible values of its argument or arguments. Thus 'If x is a man, x is mortal' is necessary, because it is true for any possible value of x. | |
From: Bertrand Russell (On the Notion of Cause [1912], p.175) | |
A reaction: This is presumably the intermediate definition of necessity, prior to modern talk of possible worlds. Since it is a predicate about functions, it is presumably a metalinguistic concept, like the semantic concept of truth. |