Full Idea
To recognise abstract terms as perfectly proper items of a vocabulary depends upon allowing that all that is necessary for the lawful introduction of a range of expressions into the language is a coherent account of how they are to function in sentences.
Gist of Idea
Abstract terms are acceptable as long as we know how they function linguistically
Source
Michael Dummett (Frege philosophy of mathematics [1991], Ch.16)
Book Reference
Dummett,Michael: 'Frege: philosophy of mathematics' [Duckworth 1991], p.208
A Reaction
Why can't the 'coherent account' of the sentences include the fact that there must be something there for the terms to refer to? How else are we to eliminate nonsense words which obey good syntactical rules? Cf. Idea 9872.
Related Idea
Idea 9872 Abstract objects need the context principle, since they can't be encountered directly [Dummett]