Regressus and Empiricism in the Controversy about Galileo's Lunar Observations

This paper defends a version of J. H. Randall's thesis that modern empiricism is rooted in the Scholastic regressus method epitomized by Jacopo Zabarella in De Regressu (1578). Randall's critics note that the empirical practice of Galileo and his contemporaries does not follow Zabarella. However, Zabarella's account of the regressus is imprecise, which permitted an interpretation introducing empirical hypothesis testing into the framework. The discourse surrounding Galileo's lunar observations in Sidereus Nuncius (1610) suggests that both Galileo and his interlocutors amended the regressus method in this way, such that a developmental narrative links Scholastic logic to Galilean science.