In Aristotle’s logic, the basic ingredients of reasoning are given in terms of inclusion and exclusion relations, of the sort graphically captured many years later by the device of Venn diagrams. He begins with the notion of a patently correct sort of argument, one whose evident and unassailable acceptability induces Aristotle to refer to is as a ‘perfect deduction’ (APr. 24b22–25). Generally, a deduction (sullogismon), according to Aristotle, is a valid or acceptable argument. More exactly, a d