Full Idea
Maddy dispenses with pure sets, by sketching a strong set theory in which everything is either a physical object or a set of sets of ...physical objects. Eventually a physiological story of perception will extend to sets of physical objects.
Gist of Idea
Maddy replaces pure sets with just objects and perceived sets of objects
Source
report of Penelope Maddy (Realism in Mathematics [1990]) by Stewart Shapiro - Thinking About Mathematics 8.3
Book Reference
Shapiro,Stewart: 'Thinking About Mathematics' [OUP 2000], p.223
A Reaction
This doesn't seem to find many supporters, but if we accept the perception of resemblances as innate (as in Hume and Quine), it is isn't adding much to see that we intrinsically see things in groups.