The study of medieval science enjoyed a golden period, first in the early part of the century with the indefatigable researches of Lynn Thorndike and George Sarton and then in this half century, with translations of and commentaries on the great works of medieval scientists like Oresme, Buridan, and Albertus Magnus by scholars such as Edward Grant and Marshall Claggett. In the last two decades of the century, however, medieval science has retreated into semi-hibernation, partly due to the shifting priorities of history of science as a field, but also do to a reconceptualization of what history of science is. The works which have appeared lately have taken the subject in a direction away from the positivistic search for precursors and philological textual analysis toward the synthetic understanding of context and contingencies.
Joel Kaye now enters the fray with Economy and Nature in the Fourteenth Century which suggests that the metaphors and methodology of fourteenth-century natural philosophy -- what we understand to be proto-science -- derive from late thirteenth- and early fourteenth-century economic thought reflecting economic realities of the time. The thesis is not surprising, for if one paradigm has become apparent in the last quarter century in history of science, it is that theoretical researches then, as now, are affected as or more strongly by social conditions than by their own internal logic.
The social conditions feeding into Kaye's investigation are the intertwined stories of the rise of the university, the expansion of a monetary economy throughout Europe, the university Schoolmen's administrative (and therefore financial) duties in their universities, and an increase in their interest in quantification. He seeks to prove that the first three directed the last, even though the Schoolmen never admitted the economic influences. Of course, there was good reason for them not to admit them, since economics treats money, and money suggests usury (although by the end of thirteenth century they tended to defend "reasonable" profits by merchants and "expected" returns on capital investments in businesses, including monasteries). Melding economic history, the history of economic thought, and the history of science, Kaye proceeds to analyze the theoretical underpinnings of the thirteenth- century commercial revolution, although his footnotes are sparse with respect to real-world mechanisms of this revolution, tending more to the Scholastic interpretations. He suggests that the reconceptualization of money from a discrete commodity to a continuum and from an arithmetical balance to a proportional (i.e. geometric) trade-off involving more factors than just price and quantity paved the way for the fourteenth- century thinkers to contemplate the continuum of motion and the proportional relations between mass, velocity, and force (with a digression into the impetus theory of Buridan). In this way, the proto-scientists could measure incommensurables, consider quantities rather than qualities, and describe dynamic approximations rather than knowable perfections.
Kaye adduces evidence of proto-scientific thought through careful exposition of the economic writings of Henry of Ghent, Godfrey of Fontaines, Albertus Magnus, Thomas Aquinas, Peter John Olivi, Geraldus Odonis, Jean Buridan, and last but not least, Nicole Oresme on usury and commentaries on the economics in Aristotle's Ethics V.3-5. In this published version of his 1991 dissertation (Pennsylvania), he chooses five concepts with which to look at the similar elements in economic and scientific thought: "mathematics and the geometry of exchange", "equality, the mean, and equalization in exchange", "money as medium and measure", "relation and relativity of value", and "the social geometry of monetized society." In his roughly chronological treatment, he returns to one or more of these concepts as sub-sections of each chapter, suggesting how these concepts were understood at the time and how they seem to be echoed in contemporary proto-scientific writings. In some ways, the project might have been more fluid had these five topics become five chapters, for as it stands there is a certain sense of repetition and a large amount of self- reference in the notes as Kaye passes over the same or similar ground as he did in previous chapters. But with a subject matter as subtle as this, there may be no entirely smooth presentation method. Ultimately, since the Schoolmen never acknowledged the correlations, Kaye is left to show that economics did play a role in these men's lives, that these same men did consider economic questions in some treatises and scientific ones in others, and that the two types of works share an unlikely degree of similitude in thought and metaphor for there not to have been an influence.
While enticing, Kaye's work is not entirely convincing. In some cases he slights material some readers may have liked him to deal with, like evidence for the shift to a monetized economy, particularly how fourteenth century monetization was qualitatively different than eleventh or twelfth century economic growth. The other problem is that the direction of the interrelated effects remains unclear, or at least unproven. Kaye does show that the economic exegesis predates the scientific, although he sometimes relies on rather tenuous arguments, such as claiming that Peter Olivi's works were seminal influences on Buridan and Oresme, even though they had been banned in 1304 (shades of "Name of the Rose", perhaps). He also virtually ignores geometrical optics (Witello having written his Perspectiva about 1270) and whether they, too, intersected with economic metaphors and fails to suggest why economic thought should be privileged over visual thought in the creation of proto-science (he does, however, devote a section to the idea of visualizing geometric figures [204f]). One wonders why economics would more strongly influence scholars in Oxford or Paris than in Italy, which remained economically active throughout the early middle ages; should we then return to the pre-war conception that there was simply "something" about Oxford or Paris?
Kaye notes the conceptual and metaphoric parallels between the relativity of monetary debasements and revaluations and the relativity of the size of the universe and relativity of motion (particularly with a nod to the Copernican question of the relativity of the Earth's rotation which Oresme considered; see 237ff); yet while the Schoolmen's arguments contend that if everything is scaled proportionally there is no perceptual difference to the observer, although theoretically this should be the case with debasements, experientially consumers certainly do feel effects of the changing value of money. And he himself admits that in the middle of the century, with repercussions from revaluations and the plague, people did indeed notice changes in their lifestyle (20-8).
To my mind, Kaye has described correlation but not necessarily cause, a suggestion but not necessarily a conclusion. But, as he admits early on in the book, his is not a thesis which was ever explicitly acknowledged by the Schoolmen and we must therefore not expect a smoking gun. In arguing something which is likely unprovable, he has engaged in an uphill struggle but one with promise. He certainly reemphasizes the fact that the Scholastics were not isolated from the society of their day, however much we may be inclined to picture them in their ivory towers. In a decade or two scholars may indeed look back to Kaye's book and others like it -- for example, Richard Hadden's On the Shoulder of Merchants (SUNY, 1994), Lisa Jardine's later but related Worldly Goods (Macmillan, 1996), and others which investigate this area -- and take it as axiomatic that science arose from commerce. At the moment, what we can say is that economic thought may have been yet another element in conditioning the mind of fourteenth-century natural philosophers.