Full Idea
Dummett aimed to characterise realism in terms not of the mind-independence of the entities but of the validity of bivalence for sentences referring to them.
Gist of Idea
Dummett saw realism as acceptance of bivalence, rather than of mind-independent entities
Source
report of Michael Dummett (Realism [1982]) by Michael Potter - The Rise of Analytic Philosophy 1879-1930 21 'Lang'
Book Reference
Potter,Michael: 'The Rise of Anaytic Philosophy 1879-1930' [Routledge 2020], p.142
A Reaction
Hence he called himself a 'philosopher of language', rather than a 'philosopher of thought'. Philosophers of language are more likely to end up as anti-realists, I suspect.