From pages 154-155 of Frank Knight’s 1940 review essay titled “‘What Is Truth’ in Economics?” as this essay is reprinted in Knight’s 1956 collection, On the History and Method of Economics:
Economics and other social sciences deal with knowledge and truth of a different category from that of the natural sciences, truth which is related to sense observation – and ultimately even to logic – in a very different way from that arrived at by the methodology of natural science. But it is still knowledge about reality.
The fact that economists, with relatively rare exception, cannot conduct controlled laboratory experiments which allow a focus on the behavior of a small handful of variables does not render the knowledge arrived at by economic scholarship – observation, research, and reasoning – unscientific…
To fancy that one can gain an adequate understanding of the workings of the economy merely by carefully observing and measuring the relatively few objective pieces of quantified data that are typically available to economic researchers – “the” unemployment rate, “the” four-digit concentration ratio of this and that industry, “the” Gini coefficient for this and that country…is foolish. All such observable empirical facts are the results of vast and complex plan formation and modification and human interactions. Observable facts about the economy have no meaning on their own, and they are not – or ought not to be – the subject-matter of economics.