Robert Boyle on Ferments and Fermentation: Abstract

Ashley J. Inglehart

Indiana University

The concept of a ferment has described a vast array of processes. These include digestion; putrefaction; coagulation; internal heat of the blood and motion of the heart; the production of wine, bread, beer, cheese, and spirits; transmutation, the philosopher’s stone and the alkahest; and the generation or growth of animals, minerals, and vegetables. The process of fermentation, moreover, has a central role in both vitalistic theories and those which adhere more closely to the mechanical philosophy of the seventeenth century. A telling feature of the history of the term ‘fermentation’ can be found in the term’s Latin root, fervere, meaning “to boil.” When ‘ferment’ was first introduced into Middle English, it referred to some active ingredient, such as leaven or yeast, which was the cause of fermentation. This ferment stands in contrast to the fermentum, or that which is acted upon. Thus, for a considerable part of its history, fermentation involved (1) an active ingredient, (2) a passive matter acted upon by means of the ferment involving (3) heat. Moreover, the process of fermentation implied a substantial change, just as dough is transformed into bread and juice into wine. This paper looks at Robert Boyle’s treatment of ferments and fermentation as discussed throughout his corpus. Boyle addresses the topic of fermentation in no less than forty treatises spanning over thirty years. Curiously, however, no work has been published looking specifically at Boyle’s treatment of ferments and fermentation and how his views might have changed over time. By 1675, Boyle restricted his application of ‘fermentation’ to certain processes, and he remained surprisingly consistent about it for the remainder of his career. This notion of fermentation, perhaps derived from his experiments with Spirit of Wine, applied to his views on air, liquors, and even blood. Boyle’s understanding of fermentation is, moreover, central to his more general world view. For example, in his Physiological Essays, Boyle lists fermentation as being among the “more obvious and familiar Qualities or states of Bodies,” along with heat, cold, fluidity, hardness, and weight, that act as emergent properties from “the more Primitive” qualities of bulk, shape, and motion. Because fermentation plays a key role in much of Boyle’s work, I intend to use Boyle’s writings on fermentation as a test case for the evolution of his mechanical philosophy. I will show that his notion of ‘mechanical’ became considerably restricted over time. Moreover, I aim to show that throughout Boyle’s career his treatment of fermentation was informed by both his mechanical and his experimental philosophy.