The Two Ontological Faces of Velocity

This article presents a formalization of velocity in the context of a realist and perspectivalist upper ontology like BFO. It argues that the term “velocity” can refer to two different entities: a motion-velocity, which is a process profile characterizing a motion process; and an object-velocity, which is a disposition inhering in the moving object. Three different kinds of motion-velocity are presented: left-velocity, right-velocity and bilateral velocity. Motion-velocity could exist without object-velocity, as revealed by a thought experiment presented by Tooley; but in our world, Newton's first law of inertia implies that every object has both an inertial disposition and a closely related but different disposition that we call “object-velocity.” Those two dispositions are realized by the right-velocity. The left-velocity is a trigger of the inertial disposition, and brings into existence the object-velocity.