Full Idea
We could say that abstraction is just mereological subtraction of universals.
Gist of Idea
Maybe abstraction is just mereological subtraction
Source
David Lewis (Against Structural Universals [1986], 'Uninstantiated')
Book Reference
Lewis,David: 'Papers in Metaphysics and Epistemology' [CUP 1999], p.103
A Reaction
This only works, of course, for the theories that complex universals have simpler universals as 'parts'. This is just a passing surmise. I take it that abstraction only works for a thing whose unity survives the abstraction.