 In short, it seems clear that the Sophistical Refutations was instrumental in prompting medieval interest in insolubles. But more must have been involved too. Martin (1993) suggests a connection with theories of obligations (cf.  Section 3.3  below). Before medieval logicians could formulate genuine Liar-type paradoxes, they first had to go well beyond anything found in Aristotle’s text. At present we cannot say whether they did this on the basis of some still unidentified ancient source or whether it was through their own intellectual power and logical insight.