Full Idea
Utilitarians believe that actions and dispositions are only virtuous because they promote another end than virtue.
Gist of Idea
Virtues only have value because they achieve some further end
Source
John Stuart Mill (Utilitarianism [1861], Ch.4)
Book Reference
Mill,John Stuart: 'Utilitarianism (including On Liberty etc)', ed/tr. Warnock,Mary [Fontana 1962], p.289