Abstract

Bošković’s distinction between two kinds of velocities – velocity in the first act, or potential velocity, and velocity in the second act, or actual velocity – is considered in respect to the concept of instantaneous velocity as defined by calculus differentialis. Contrary to the seeming inconsistency of Bošković’s duality of velocities and the concept of instantaneous velocity, due to a critical examination of logical and methodological foundations of the calculus, the article shows that the duality of velocities is consistent with the interpretations of instantaneous velocity given by Oresme, Euler and Maclaurin, as with the definition of instantaneous velocity according to the rigorous Cauchyan founding of the calculus. Bošković’s duality of velocities is also shown to be consistent with Aristotelian-scholastic doctrine of potentiality and actuality, especially in its domain related to the nature of continuous motion.