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]