In this essay, I use a general argument about the evidential role of data in ongoing inquiry to show that it is fruitful for economic historians and historians of economics to collaborate more frequently. The shared aim of this collaboration should be to learn from past economic experience in order to improve the cutting edge of economic theory. Along the way, I attack a too rigorous distinction between the history of economics and economic history. By drawing on the history of physics, I argue that the history of a discipline can be a source of important evidence in ongoing inquiry. My argument relies on the claim that it is a constitutive element of science that evidence is never discarded forever and is thus historical in nature. In the final section, I offer a case study by explaining a research proposal that turns on a long-running data-set Babylonian whole-sale prices of six commodities noted in pre-Hellenistic and Hellenistic times. To motivate my reading of this data-set, I critically discuss Aristotle′s successful attempt to distinguish between astrology and political economy.