1. Generality Certain characteristics of the subject are clear. To begin with, we do not in this subject deal with particular things or particular properties: we deal formally with what can be said about any thing or any property. We are prepared to say that one and one are two, but not that Socrates and Plato are two. . . .
Bertrand Russell (1872 - 1970)
Source: Chapter XVIII of Introduction to Mathematical Philosophy, Russell