[Milton Friedman] believes in an oversimplified quantitative relationship between a measurable quantity of money and the price level. You must leave … - Friedrich Hayek

The social sciences building at the University of Chicago indeed still bears since it was built 40 years ago on its outside an inscription taken from the famous physicist Lord Kelvin: "When you cannot measure, your knowledge is meager and unsatisfactory." I will admit that that may be true, but it is certainly not scientific to insist on measurement where you don't know what your measurements mean. There are cases where measurements are not relevant. What has done much damage to microeconomics is striving for a pseudo-exactness by imitating methods of the physical sciences which have to deal with what are fundamentally much more simple phenomena. And the assumption that it is possible to ascertain all the relevant particular facts still completely dominates the alternative methods of dealing with our constitutional ignorance, which economists have tried to overcome. This of course, is what has come to be called macroeconomics as distinct from microeconomics.

The illiterate expression ‘given data’ constantly recurs in Lange. It appears to have an irresistable attraction to mathematical economists because it doubly assures them that they know what they do not know. It seems to bewitch them into making assertions about the real world for which they have no empirical justification whatever.

Since only actions aimed at perceived benefit to others were, to Aristotle's mind, morally approved, actions solely for personal gain must be bad. That commercial considerations may not have affected the daily activities of most people does not mean however that over any prolonged period their very lives did not depend on the functioning of a trade that enabled them to buy essentials. That production for gain which Aristotle denounced as unnatural had -- long before his time -- already become the foundation of an extended order far transcending the known needs of other persons.