Full Idea
In the idea of learning concepts by 'abstraction', experiences of the instances provide evidence about which of the shared properties of things in a concept's extension are 'criterial' for being in the concept's extension.
Gist of Idea
Abstractionism claims that instances provide criteria for what is shared
Source
Jerry A. Fodor (LOT 2 [2008], Ch.5.2 n6)
Book Reference
Fodor,Jerry A.: 'LOT 2: the Language of Thought Revisited' [OUP 2008], p.135
A Reaction
Fodor is fairly sceptical of this approach, and his doubts are seen in the scare-quotes around 'criterial'. He is defending the idea that only a certain degree of innateness in the concepts can get such a procedure off the ground.