this 'a certain stone-man is not a stone' is false by necessity, since it is impossible to suppose it is true. Terence Parsons (born 1939) argues that ancient philosophers did not experience the problem of existential import as only the A (universal affirmative) and I (particular affirmative) forms had existential import. (If a statement includes a term such that the statement is false if the term has no instances, i.e., no thing associated with the term exists, then the statement is said to have existential import with respect to that term.) Affirmatives have existential import, and negatives do not. The ancients thus did not see the incoherence of the square as formulated by Aristotle because there was no incoherence to see. He goes on to cite a medieval philosopher William of Moerbeke (1215–35 – ), In affirmative propositions a term is always asserted to supposit for something. Thus, if it supposits for nothing the proposition is false. However, in negative propositions the assertion is either that the term does not supposit for something or that it supposits for something of which the predicate is truly denied. Thus a negative proposition has two causes of truth. And points to Boethius' translation of Aristotle's work as giving rise to the mistaken notion that the form has existential import. But when Boethius (477 – 524 AD) comments on this text he illustrates Aristotle's doctrine with the now-famous diagram, and he uses the wording 'Some man is not just'. So this must have seemed to him to be a natural equivalent in Latin. It looks odd to us in English, but he wasn't bothered by it. Modern squares of opposition In the 19th century, George Boole (November 1815 – 8 December 1864) argued for requiring existential import on both terms in particular claims ( and ), but allowing all terms of universal claims ( and ) to lack existential import. This decision made Venn diagrams particularly easy to use for term logic. The square of opposition, under this Boolean set of assumptions, is often called the modern Square of opposition. In the modern square of opposition, and claims are contradictories, as are and , but all other forms of opposition cease to hold; there are no contraries, subcontraries, subalternations, and superalternations. Thus, from a modern point of view, it often makes sense to talk about 'the' opposition of a claim, rather than insisting, as