Unlike the position that exists in the physical sciences, in economics and other disciplines that deal with essentially complex phenomena, the aspects of the events to be accounted for about which we can get quantitative data are necessarily limited and may not include the important ones. While in the physical sciences it is generally assumed, probably with good reason, that any important factor which determines the observed events will itself be directly observable and measurable, in the study of such complex phenomena as the market, which depend on the actions of many individuals, all the circumstances which will determine the outcome of a process, for reasons which I shall explain later, will hardly ever be fully known or measurable.

It seems to me that this failure of the economists to guide policy more successfully is closely connected with their propensity to imitate as closely as possib…

While in the physical sciences the investigator will be able to measure what, on the basis of a prima facie theory, he thinks important, in the social sciences…

On the other hand, the economists are at this moment called upon to say how to extricate the free world from the serious threat of accelerating inflation which…

I often say that when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot express it in nu…

I often say that when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot express it in nu…

'I belong to the don't-know school of economics.'