Full Idea
The early psychological approaches to concepts took a definitional approach. ...but this view does not have any way of distinguishing typical and atypical category members (...as when a trout is a typical fish and an eel an atypical one).
Gist of Idea
The classical definitional approach cannot distinguish typical and atypical category members
Source
Gregory L. Murphy (The Big Book of Concepts [2004], Ch. 2)
Book Reference
Murphy,Gregory L.: 'The Big Book of Concepts' [MIT 2004], p.12
A Reaction
[pp. 12 and 22] Eleanor Rosch in the 1970s is said to have largely killed off the classical view.