Full Idea
We will define a function of one variable as 'predicative' when it is of the next order above that of its arguments, i.e. of the lowest order compatible with its having an argument.
Gist of Idea
A one-variable function is only 'predicative' if it is one order above its arguments
Source
Bertrand Russell (The Theory of Logical Types [1910], p.237)
Book Reference
Russell,Bertrand: 'Essays in Analysis', ed/tr. Lackey,Douglas [George Braziller 1973], p.237
A Reaction
'Predicative' just means it produces a set. This is Russell's strict restriction on which functions are predicative.
Related Idea
Idea 21558 'Predicative' norms are those which define a class [Russell]