…is from Page 10 of Ludwig von Mises’ 1949 treatise Human Action (emphasis added):
It is true that economics is a theoretical science and as such abstains from any judgement of value. It is not its task to tell people what ends they should aim at. It is a science of the means to be applied for the attainment of ends chosen, not, to be sure, a science of the choosing of ends. Ultimate decisions, the valuations and the choosing of ends, are beyond the scope of any science. Science never tells a man how he should act; it merely shows how a man must act if he wants to attain definite ends.
Far too many economists, both in Mises’ day and today, make the very mistake Mises warns against: treating economics as a science of the choosing of ends. They consider themselves enlightened for building models that can maximize this or minimize that, and then call for said models to influence policy. But building models like such, as Jim Buchanan said in his 1964 paper What Should Economist Do?, is the purview not of economics, but of applied mathematics. Indeed, anyone with even an elementary level of calculus would find such a task trivially easy.
But economics is not this; it is not merely optimizing some constrained function with some universally desired “social goal.” Economics is the study of exchange; Of competing interests for scarce resources and the institutions that arise to deal with these issues. In short, the study of human action.