 Dumbleton’s treatise on insolubles constitutes a very small part of his long treatise, running to some 400,000 words, entitled Summa Logicae et Philosophiae Naturalis. It is preserved in 21 manuscripts, though two omit the first part, on logic. Part I: Summa Logicae opens with a short treatise on signification. This is essential for underpinning and defending Dumbleton’s approach to the insolubles, for he argues for a version of cassatio: insolubles signify in such a way that they fail to express propositions. The reason for this failure, he says, is that an utterance, spoken or written, is a proposition only if it communicates something from the speaker to the hearer. 