Full Idea
Quine charges that the axiom of Reducibility both undoes the effect of the ramification, and commits the theory to a platonist view of propositional functions (which is a theory of sets, once use/mention confusions are cleared up).
Gist of Idea
Reducibility undermines type ramification, and is committed to the existence of functions
Source
report of Willard Quine (Set Theory and its Logic [1963], p.249-58) by Bernard Linsky - Russell's Metaphysical Logic 6.1
Book Reference
Linsky,Bernard: 'Russell's Metaphysical Logic' [CSLI 1999], p.92