 This critique of Aristotle’s theory of projectile motion did not come out of nowhere. Aristotle relied on a concept of natural motion, and that, in turn, relied on a concept of natural place: natural motion was motion towards the natural place of a body (i.e. motion downwards in the case of earth, and motion upwards in the case of fire). (Aristotle, Physics IV.5, 212b30–213a5) Ockham is already quite equivocal about the concept of natural place: and this is for several reasons.