This book discusses the impetus-based physics of the Jesuit natural philosopher and mathematician Honoré Fabri, a senior representative of Jesuit scientists during the period between Galileo's death and Newton's Principia. It shows how Fabri, while remaining loyal to a general Aristotelian outlook, managed to reinterpret the old concept of “impetus” in such a way as to assimilate into his physics building blocks of modern science, like Galileo’s law of fall and Descartes’ principle of inertia. This account of Fabri’s theory is (...) a novel one, since his physics is commonly considered as a dogmatic rejection of the New Science, not essentially different from the medieval impetus theory. This book shows how New Science principles were taught in Jesuit Colleges in the 1640s, thus depicting the sophisticated manner in which new ideas were settling within the lion’s den of Catholic education. (shrink)

This article offers the first critical edition of the most important version of Francis of Marchia's famous question 1 of his commentary on Book IV of the Sentences, in which the Franciscan theologian puts forth his virtus derelicta theory of projectile motion. The introduction attempts to place Marchia's theory in its proper context. The theory might seem to us an obvious improvement on Aristotle, but rather than an immediate and complete break with tradition that all scholastics quickly adopted, Marchia's virtus (...) derelicta was more a stage in a gradual process that had begun many decades before and did not find universal acceptance among his first successors. Moreover, Marchia himself did not take the theory to what might seem the obvious conclusion that Jean Buridan would draw, because Marchia employed the virtus derelicta to explain more phenomena than just projectile motion. (shrink)

Galileo proposed what has been called a proto-inertial principle, according to which a body un horizontal motion will conserve its motion. This statement is only true in counterfactual circumstances where no impediments are present. This paper analyzes how Galileo could have been justified in ascribing definite properties to this idealized motion. This analysis is then used to better understand the relation of Galileo’s proto-inertial principle to the classical inertial principle.