 Many contributors to economics were actively engaged in scientific and philosophical societies. The members of the Hartlib Circle of mid-seventeenth century England conjoined natural science with economic objectives, not least alchemical pursuits as a solution to the dire shortage of coins (see Wennerlind 2014). Its best known member, the Irish philosopher William Petty, was a leading contributor to monetary theory and demography, as well as a founding member of the Royal Society. His economic writings fill two large volumes and he broached the concepts of the transactions level and the velocity of money, two key variables that cemented the core principle of the quantity theory of money. Two of the most renowned philosophers of the period, Locke and Isaac Newton, were actively engaged in debates over the value of the currency, specifically when Newton served as Warden and then Master of the Mint (see Westfall 1981). Hume and Smith were members of the Edinburgh Philosophical Society (Hume was co-secretary) and were close friends of the leading contributors to mainstream science, William Cullen, Joseph Black, and James Hutton in Scotland, as well as, in Hume’s case, the French proto-evolutionist Comte de Buffon and, in Smith’s case, the French botanist Charles Bonnet. Smith’s essays on the history of astronomy and of physics, first sketched in the 1750s but updated and revised for the rest of his life, display a sophisticated command of science and the history and philosophy of science. His stance was one of fallibilism and instrumentalism, and he broached the possibility that the Newtonian system, while ascendant, would one day be superseded (see Schliesser 2017).