 From the late twelfth century there also developed in the Latin tradition what was called the logica modernorum (“contemporary logic”)—a variety of new branches of the subject not found in Aristotle. The most important of them concern the properties of terms (the analysis of the reference of words—their “supposition”—within the context of sentences (see entry on  Medieval theories: properties of terms);  consequentiae (propositional logic, by contrast with Aristotelian term logic—see entry on  medieval theories of consequence);  sophismata (deliberately ambiguous sentences and/or ones with apparently puzzling consequences that can be explained by semantic analysis, such as “Something white will be black”);  insolubles  (insolubilia—paradoxes, such as that of the Liar); and  obligations  (an argument game, involving counterfactual statements and testing the contestants’ ability to remain consistent). Specialized treatises were written on each of these topics, but the most popular textbook of all, the Treatise, known as the Summule logicales, written by  Peter of Spain  probably c. 1125–50, which combines the logica vetus and nova with a long exposition of the theory of the property of terms. Peter (whoever he was: see Peter of Spain Summaries, 1–9) was not in fact an outstanding logician, but his work, by then the standard textbook, was adapted, with enormous licence, in the mid-fourteenth century as a vehicle for his also very widely-read Summule de dialectica, by the greatest logician of the time, John Buridan. Work within the logica modernorum went on until the mid-sixteenth  century.[38]