Economy and Nature in the Fourteenth Century: Money, Market Exchange, and the Emergence of Scientific Thought (review)

Kaye “argues in this revised doctoral dissertation that the transformation of the conceptual model of the natural world, accomplished within the technical disciplines of the universities of Oxford and Paris c. 1260–1380, was strongly influenced by the rapid monetization of European society taking place over this same period, beyond the university and outside the culture of the book” (2). Kaye admits that, in their natural-science work, fourteenth-century philosophers did not explicitly take money as a model for quantification, but he wants to claim that because scholars such as Thomas Bradwardine and his fellow Mertonians, John Buridan, and Nicole Oresme had abundant daily contact with business, they experienced “perceptual shifts . . . grounded in the experience and comprehension of monetized society” (2).

It is well known that Oresme, one of the most important figures in the new physics of the fourteenth century and an advisor to King Charles V, wrote a treatise warning Charles against too frequent debasements of his coinage. In addition, Kaye assembles striking evidence that fourteenth-century natural philosophers were often assigned tasks associated with the financial affairs of their colleges and universities. Given the nature of the evidence, Kaye cannot prove an impact of money on the sensibilities of these men, but what he does is to show that at the same time, or even before, these thinkers began to develop methods of quantification in physics, they were applying similar concepts, for instance of latitudes and degrees, to economic problems. Thus, it was argued that the just price for a given item at a given time is not some exact value, but may range within a latitude of prices, all of which might be considered just. As William Heytesbury or Richard Swineshead asked whether increase and decrease of rarity and density depend on absolute or relative increases or decreases in size, so did legal, ethical, and economic thinkers debate the range within which the price given or received could vary from the just price without requiring restitution. According to law, if a person paid at least half of the just price, then he did not have to pay an additional amount to the seller. But what about overpayment? Could the seller receive up to twice the just price without violating justice, or was the margin of error on the high side only half the just price as well?

The virtue of this book is its clear demonstration of the interconnections between medieval economic and physical thought hidden when historians of economics and historians of science do not read each other’s work. As a historian of mathematics and science, I was fascinated with the evidence that Kaye provides about the parallels between Peter John Olivi’s economic writings and contemporary writings on the “new physics.” Ironically, Olivi’s ideas were known to historians until recently only through the liberal quotations of them, without attribution, in the sermons of San Bernardino da Siena a century later—Olivi’s writings themselves having been censured and forbidden in 1319. With the correct chronology now apparent, it is evident that quantification in economic thought was at least contemporary with, and perhaps even earlier than, quantification in physics.

This finding raises a whole range of interesting possibilities, because medieval economic theorists were very clear that the prices of goods and services depend not on their absolute values in the great chain of being, so to speak, but on their usefulness to humans and on human needs and preferences. Trade, these theorists argued, was essential to human welfare. A merchant who exercised good judgment in buying goods where they were plentiful and selling them where they were not was entitled, the theorists said, to a profit proportional to his skills. Moreover, despite the Biblical prohibition of usury, medieval scholars argued that a borrower might justifiably agree to pay back a lender an additional sum (called “interesse”) beyond what he...