Full Idea
A necessary (but not sufficient) condition for x's being the intended referent of S's use of a name is that x should be the source of the causal origin of the body of information that S has associated with the name.
Gist of Idea
The intended referent of a name needs to be the cause of the speaker's information about it
Source
Gareth Evans (The Causal Theory of Names [1973], §I)
Book Reference
Evans,Gareth: 'Collected Papers' [OUP 1985], p.13
A Reaction
This is Evans's adaptation of Kripke's causal theory of names. This cries out for a counterexample. I say something about General Montgomery, having just listened to 'Monty's Double' give a talk, believing it was Montgomery?