Full Idea
Concepts and other aspects of mental representation have content but not (normally) meaning (unless they are also expressions in a language used in communication).
Gist of Idea
Concepts in thought have content, but not meaning, which requires communication
Source
Gilbert Harman ((Nonsolipsistic) Conceptual Role Semantics [1987], 12.1.2)
Book Reference
Harman,Gilbert: 'Reasoning Meaning and Mind' [OUP 1999], p.208
A Reaction
Given his account of meaning as involving some complex 'role', he has to say this, though it seems a dubious distinction, going against the grain of a normal request to ask what some concept 'means'. What is 'democracy'?