Full Idea
I call 'abstractionism' the doctrine that a concept is acquired by a process of singling out in attention some one feature given in direct experience - abstracting it - and ignoring the other features simultaneously given - abstracting from them.
Gist of Idea
'Abstractionism' is acquiring a concept by picking out one experience amongst a group
Source
Peter Geach (Mental Acts: their content and their objects [1957], §6)
Book Reference
Geach,Peter: 'Mental Acts: Their content and their objects' [RKP 1971], p.18
A Reaction
Locke seems to be the best known ancestor of this view, and Geach launches a vigorous attack against it. However, contemporary philosophers still refer to the process, and I think Geach should be crushed and this theory revived.