Full Idea
To put the predicate letter 'F' in a quantifier is to treat predicate positions suddenly as name positions, and hence to treat predicates as names of entities of some sort.
Gist of Idea
Putting a predicate letter in a quantifier is to make it the name of an entity
Source
Willard Quine (Philosophy of Logic [1970], Ch.5)
Book Reference
Quine,Willard: 'Philosophy of Logic' [Prentice-Hall 1970], p.66
A Reaction
Quine's famous objection to second-order logic. But Quine then struggles to give an account of predicates and properties, and hence is accused by Armstrong of being an 'ostrich'. Boolos 1975 also attacks Quine here.