Full Idea
Russell and Whitehead took arithmetic to be higher-order logic, ..and came close to identifying numbers with numerical quantifiers.
Gist of Idea
Russell and Whitehead took arithmetic to be higher-order logic
Source
report of B Russell/AN Whitehead (Principia Mathematica [1913]) by Harold Hodes - Logicism and Ontological Commits. of Arithmetic p.148
Book Reference
-: 'Journal of Philosophy' [-], p.148
A Reaction
The point here is 'higher-order'.