<P> Perhaps the essence of a notion of diminishing marginal utility can be found in Aristotle's Politics, wherein he writes </P> <P> external goods have a limit, like any other instrument, and all things useful are of such a nature that where there is too much of them they must either do harm, or at any rate be of no use </P> <P> (There has been marked disagreement about the development and role of marginal considerations in Aristotle's value theory .) </P> <P> A great variety of economists have concluded that there is some sort of interrelationship between utility and rarity that affects economic decisions, and in turn informs the determination of prices . Diamonds are priced higher than water because their marginal utility is higher than water . </P>

Who gave the law of diminishing marginal utility