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Single Idea 21566

[catalogued under 5. Theory of Logic / E. Structures of Logic / 5. Functions in Logic]

Full Idea

By a 'propositional function' I mean something which contains a variable x, and expresses a proposition as soon as a value is assigned to x. That is to say, it differs from a proposition solely by the fact that it is ambiguous.

Gist of Idea

'Propositional functions' are ambiguous until the variable is given a value


Bertrand Russell (The Theory of Logical Types [1910], p.216)

A Reaction

This is Frege's notion of a 'concept', as an assertion of a predicate which still lacks a subject.

Book Reference

Russell,Bertrand: 'Essays in Analysis', ed/tr. Lackey,Douglas [George Braziller 1973], p.216

Related Idea

Idea 8488 A concept is a function whose value is always a truth-value [Frege]