Full Idea
A 'singularist', who refers to objects one at a time, must resort to the language of sets in order to replace plural reference to members ('Henry VIII's wives') by singular reference to a set ('the set of Henry VIII's wives').
Gist of Idea
If you only refer to objects one at a time, you need sets in order to refer to a plurality
Source
Oliver,A/Smiley,T (What are Sets and What are they For? [2006], Intro)
Book Reference
'Metaphysics (Philosophical Perspectives 20)', ed/tr. Hawthorne,John [Blackwell 2006], p.124
A Reaction
A simple and illuminating point about the motivation for plural reference. Null sets and singletons give me the creeps, so I would personally prefer to avoid set theory when dealing with ontology.