A number of writers on history of science have made it clear that in using the term “motive force” in the “Principia,” Newton referred to what we now call “impulse.” With this interpretation, there is a simple and plausible connection between the laws of impact as they were known and described in Newton's day and Newton's formulation of the Laws of Motion in the “Principia,” and we speculate that Newton might have been motivated by such a perception.