Philosophers are screwed nowadays. If they apply the scientific method and reductionism to social sciences topics they cut away too much. If they stay with vague notions which do not cut away the details they are accused of being vague. The vaguesness is there for a reason: It it kind of abstraction of the essential complexity of the abstracted domain.
EDIT: Mestroyer was the first one to find a bug that breaks this idea. Only took a couple of hours, that's ethics for you. :)
In the last Stupid Questions Thread, solipsist asked
People raised valid points, such as ones about murder having generally bad effects on society, but most people probably have the intuition that murdering someone is bad even if the victim was a hermit whose death was never found out by anyone. It just occurred to me that the way to formalize this intuition would also solve more general problems with the way that the utility functions in utilitarianism (which I'll shorten to UFU from now on) behave.
Consider these commonly held intuitions: