Full Idea
Moral rules which forbid mankind to hurt one another are more vital to human well-being than any maxims about some department of human affairs; ..though in particular cases a social duty is so important, as to overrule any general maxim of justice.
Gist of Idea
Moral rules protecting human welfare are more vital than local maxims
Source
John Stuart Mill (Utilitarianism [1861]), quoted by Gordon Graham - Eight Theories of Ethics Ch.7
Book Reference
Graham,Gordon: 'Eight Theories of Ethics' [Routledge 2004], p.136
A Reaction
The qualification is realistic, but raises the question of whether an 'act' calculation will always overrule any 'rule'. Maybe rule utilitirianism is just act utilitarianism, but ensuring that the calculations are long-term and extensive. (1871 edn)