ABSTRACT
The first clear and consistent version of CT can be found in Gottlob Frege's paper ‘On Sense and Reference’ of 1892. Of course, Frege's theory is not about mental reference as such but about linguistic reference: he does not speak of acts, contents and objects but of expressions, senses and referents. (We use ‘referent’ instead of ‘reference’ because the latter seems to designate the act of referring, the former the entity referred to.) However, there is a direct correspondence between the mental and the linguistic terminologies, and the two theories can in fact be translated, one into the other: https://www.niso.org/standards/z39-96/ns/oasis-exchange/table">
Frege
Content theory
Expression
↔
Act
Sense
↔
Content
Referent
↔
Object
