Full Idea
The bringing of an object under a concept is merely the recognition of a relation which previously already obtained, [but in the abstractionist view] objects are essentially changed by the process, so that objects brought under a concept become similar.
Gist of Idea
Our concepts recognise existing relations, they don't change them
Source
Gottlob Frege (Review of Husserl's 'Phil of Arithmetic' [1894], p.324)
Book Reference
-: 'Mind July 1972' [-], p.324
A Reaction
Frege's view would have to account for occasional misapplications of concepts, like taking a dolphin to be a fish, or falsely thinking there is someone in the cellar.