Full Idea
It makes a very great difference whether you refer to the person directly, or speak about him.
Gist of Idea
Referring to a person, and speaking about him, are very different
Source
Seneca the Younger (Letters from a Stoic [c.60], 117.13), quoted by A.A. Long - Hellenistic Philosophy 4.3.2
Book Reference
Long,A.A.: 'Hellenistic Philosophy' [Duckworth 1986], p.136
A Reaction
We seem to think that the distinctiveness of reference was first spotted by Frege. Not so.