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### Single Idea 21556

#### [catalogued under 6. Mathematics / C. Sources of Mathematics / 6. Logicism / b. Type theory]

Full Idea

In Russell's mature 1910 theory of types classes are defined in terms of propositional functions, and functions themselves are regimented by a ramified theory of types mitigated by the axiom of reducibility.

Gist of Idea

Classes are defined by propositional functions, and functions are typed, with an axiom of reducibility

Source

report of Bertrand Russell (The Theory of Logical Types [1910]) by Douglas Lackey - Intros to Russell's 'Essays in Analysis. p.133

Book Reference

Russell,Bertrand: 'Essays in Analysis', ed/tr. Lackey,Douglas [George Braziller 1973], p.133

Related Idea

Idea 14459
Reducibility: a family of functions is equivalent to a single type of function **[Russell]**