He added quantification to formal logic in his first work Concept Script, though his best-known work argues a number is neither a collection of things nor a property, part of his argument attempting to reduce the titular field to logic.
A John Perry essay considers this man "on Demonstratives," while Tyler Burge has written about him "and the Third Realm" and "Sinning Against" this man, a pun on the original title of his most famous essay.  That essay begins by questioning whether an identity is the a priori a-equals-a or the simplest possible case of a-equals-b. He added quantification to formal logic in his first work Concept Script, though his best-known work argues a number is neither a collection of things nor a property, part of his argument attempting to reduce the titular field to logic. Refuted by Russell, that work is his The Foundations of Arithmetic.  FTP, identify this German logician also known for his essay "On Sense and Reference."
A John Perry essay considers this man "on Demonstratives," while Tyler Burge has written about him "and the Third Realm" and "Sinning Against" this man, a pun on the original title of his most famous essay.  
Gottlob {Frege}