Full Idea
A dog cannot consider its concepts. Concepts are not things in a dog's world in the way that cats are. Concepts are things in our world, because we have language.
Gist of Idea
Concepts are things we (unlike dogs) can think about, because we have language
Source
Daniel C. Dennett (Kinds of Minds [1996], Ch.6)
Book Reference
Dennett,Daniel C.: 'Kinds of Minds' [Phoenix 1997], p.211
A Reaction
Dogs must have concepts, though, or much of their behaviour (like desperation to go for a walk, or to eat) is baffling. This is as good a proposal as I have ever encountered for the value of language. Meta-thought is a huge evolutionary advantage.