Full Idea
Armstrong dubs Quine an 'Ostrich Nominalist' (what problem??), but Quine calls himself a Platonist, because he is committed to classes or sets as well as particulars. He is not an extreme nominalist, and might best be called a Class Nominalist.
Gist of Idea
Quine is committed to sets, but is more a Class Nominalist than a Platonist
Source
report of Willard Quine (works [1961], Ch.6 n15) by Cynthia Macdonald - Varieties of Things
Book Reference
Macdonald,Cynthia: 'Varieties of Things' [Blackwell 2005], p.255
A Reaction
For someone as ontologically austere as Quine to show 'commitment' to sets deserves some recognition. If he wants to be a Platonist, I say that's fine. What on earth is a set, apart from its members?