Third, it is useful to know that Chatton’s immediate academic and intellectual world was small and intense, shaped mostly by figures and events at the University of Paris and at Oxford. His primary opponents, interlocutors, and sources were Aristotle and Augustine among the ancients, but among contemporaries and near-contemporaries he cites Thomas Aquinas, John Duns Scotus, William Ockham, Richard Campsall, Adam Wodeham, and Peter Auriol. In particular, much of his writing is so shaped by debates against Ockham (some of them conducted not only in writing but almost certainly face-to-face) that his mature views are nearly unintelligible in their details apart from Ockham’s philosophy, and vice versa. Especially illustrative of this interdependence is Chatton’s anti-Ockhamist ontological principle, often called his ‘anti-razor’.