Full Idea
Gödel defended impredicative definitions on grounds of ontological realism. From that perspective, an impredicative definition is a description of an existing entity with reference to other existing entities.
Clarification
See Idea 8721 for impredicative definitions
Gist of Idea
Realists are happy with impredicative definitions, which describe entities in terms of other existing entities
Source
report of Kurt Gödel (On Formally Undecidable Propositions [1931]) by Stewart Shapiro - Thinking About Mathematics 5.3
Book Reference
Shapiro,Stewart: 'Thinking About Mathematics' [OUP 2000], p.128
A Reaction
This is why constructivists must be absolutely precise about definition, where realists only have to do their best. Compare building a car with painting a landscape.
Related Idea
Idea 8721 An 'impredicative' definition seems circular, because it uses the term being defined [Friend]