  Third, and finally, Buridan made major contributions to certain forms of logical inquiry that originated in the medieval period. Most modern logicians know of his solutions to alethic paradoxes such as the Liar, addressed in the eighth and final chapter of ninth treatise of the Summulae, which belongs to the medieval literature of sophismata or  insolubilia.[24]  The 7th sophism Buridan considers is ‘Every proposition is false’.  The case posits “that all true propositions are annihilated while the false ones remain [in existence], and then Socrates propounds only this [proposition]: ‘Every proposition is false’” (S 9.8, 7th sophism: 965). The question is then asked whether Socrates's proposition is true or false. The arguments on each side of the question illustrate the difficulties one faces if ‘true’ and ‘false’ are interpreted strictly. The argument that it is false assumes that “it is impossible for the same proposition to be true and false when propounded in the same language and understood in the same way by everyone hearing it”, and proceeds to argue that the sophism is false because any proposition which entails its own contradictory is impossible, and therefore false. The opposite side begins by focusing on the logical form of the sophism as a universal affirmative that has no counter-instance in the case at hand, which stated that all true propositions have been annihilated with only the false ones remaining. Second, the sophism must be true because the subject and predicate terms supposit for the same things: if every proposition is false, then each and every propositional significate of the term ‘every proposition’ must be false, as it indeed is, according to the case. Finally, the sophism must be true because “it signifies only that every proposition is false; and this is how things are [ita est]”, according to the case (S 9.8, 7th sophism: 965).