Problems with Rhubarb: Accommodating Experience in Aristotelian Theories of Science

The paper examines controversies over the role of experience in the constitution of scientific knowledge in early modern Aristotelianism. While for Jacopo Zabarella, experience helps to confirm the results of demonstrative science, the Bologna Dominican Chrysostomo Javelli assumes that it also contributes to the discovery of new truths in what he calls 'beginning science'. Both thinkers use medical plants as a philosophical example. Javelli analyses the proposition 'rhubarb purges bile' as the conclusion of a yet unknown scientific proof. Zabarella uses instead hellebore, a plant that is found all over Europe, and defends the view that propositions about purgative powers of plants are based on their 'identity of substance', an identity that had become questionable with regard to rhubarb due to new empirical findings in the sixteenth century.