John Maynard Keynes on Utility

“Thus public works even of doubtful utility may pay for themselves over and over again at a time of severe unemployment, if only from the diminished cost of relief expenditure.”

“The general theory of economic equilibrium was strengthened and made effective as an organon of thought by two powerful subsidiary conceptions — the Margin and Substitution. The notion of the Margin was extended beyond [Utility]] to describe the equilibrium point in given conditions of any economic factor which can be regarded as capable of small variations about a given value,or in its functional relation to a given value.”