The greatest happiness principle: rightness is measured by aggregate well-being

Mill's foundational claim is that actions are right to the extent they promote happiness — understood broadly as pleasure and the absence of pain — and wrong to the extent they produce the opposite, with happiness defined not just for the individual acting but summed across everyone affected by the action.

This is a consequentialist standard: an action's moral status is determined entirely by its outcomes, not by the intrinsic nature of the act itself or by conformity to a rule stated in advance. Two superficially identical actions could have different moral status if their actual consequences for overall well-being differed.

Mill presents this as replacing a patchwork of independent moral rules and intuitions, which often conflict with each other in hard cases, with a single, coherent measuring standard that can in principle adjudicate any moral question by asking which available option produces the greatest net happiness.

Takeaway: when facing a moral dilemma, Mill's test asks which option produces the most overall well-being for everyone affected, not just for you.