In this paper two questions are raised: 1) Under which conditions may we say that an entity is a representation of something else? and, in particular, 2) what is the guarantee that our (mental or internal) representations correspond to or are in accord with external objects? In Hume’s opinion, three answers to the second question are possible: There is a causal relationship between represented objects and representations; representations are freely created by the mind; and God guarantees the connection between representation and represented things and events. A short historical examination of these ideas is proposed. In cognitive sciences the two questions are strictly related. In particular, Dretske, Lloyd, and Perner’s positions are presented (the causal explanation is here combined with the individuation of intrinsic features in representations that allow a medium to be a representation as such) and criticized. A fourth position is also mentioned (it was historically supported by Leibniz and presently by Jackendoff): Representation is a homomorphism. Finally, a way to solve the problem is proposed: Representations depend on the intentional act that establishes a connection between a physical or mental entity and a referent.