… is from the final paragraph of Leland Yeager’s milestone 1973 article “The Keynesian Diversion”; reprinted in Leland B. Yeager, The Fluttering Veil  (George Selgin, ed.), pp. 199-216:
Cultivation of the history of thought is more necessary in economics than in the natural sciences because earlier discoveries in economics are in danger of being forgotten; maintaining a cumulative growth of knowledge is more difficult. In the natural sciences, discoveries get embodied not only into further advances in pure knowledge but also into technology, many of whose users have a profit-and-loss incentive to get things straight. The practitioners of economic technology are largely politicians and political appointees with rather different incentives. In economics, consequently, we need scholars who specialize in keeping us aware and able to recognize earlier contributions – and earlier mistakes – when they surface as supposedly new ideas. By exerting a needed discipline, specialists in the history of thought can contribute to the cumulative character of economics.