Full Idea
Explanations in terms of syntax do not satisfactorily distinguish true variables from dummy or schematic letters. Identifying variables with pronouns, however, provides a genuine explanation of what variables are.
Gist of Idea
Variables are just like pronouns; syntactic explanations get muddled over dummy letters
Source
Peter van Inwagen (Material Beings [1990], 02)
Book Reference
Inwagen,Peter van: 'Material Beings' [Cornell 1995], p.25
A Reaction
I like this because it shows that our ordinary thought and speech use variables all the time ('I've forgotten something - what was it?'). He says syntax is fine for maths, but not for ordinary understanding.