Full Idea
Frege claims that second-order quantifiers are committed to concepts, just as singular first-order quantifiers are committed to objects.
Gist of Idea
Second-order quantifiers are committed to concepts, as first-order commits to objects
Source
report of Gottlob Frege (Grundlagen der Arithmetik (Foundations) [1884]) by Øystein Linnebo - Plural Quantification 5.3
Book Reference
'Stanford Online Encyclopaedia of Philosophy', ed/tr. Stanford University [plato.stanford.edu], p.18
A Reaction
It increasingly strikes me that Fregeans try to get away with this nonsense by diluting both the notion of a 'concept' and the notion of an 'object'.