'Everything true will be false' : Paul of Venice and a Medieval Yablo paradox
Abstract
In his Quadratura, Paul of Venice considers a sophism involving time and tense which appears to show that there is a valid inference which is also invalid. Consider this inference concerning some proposition A: A will signify only that everything true will be false, so A will be false. Call this inference B. Then B is valid because the opposite of its conclusion is incompatible with its premise. But he proceeds to argue that it is possible that B's premise could be true and its conclusion false, so B is not only valid but also invalid. Thus A and B are the basis of an insoluble---that is, a Liar-like paradox. Like the sequence of statements in Yablo's paradox, B looks ahead to a moment when A will be false, yet that moment may never come. In his Logica Parva, Paul follows the solution to insolubles found in the collection of elementary treatises known as the Logica Oxoniensis, which posits an implicit assertion of its own truth in insolubles like B. However, in the treatise on insolubles in his Logica Magna, Paul develops and endorses a different solution that takes insolubles at face value, meaning no more than is explicit in what they say. On this account, insolubles imply their own falsity, and that is why, in so falsifying themselves, they are false. We consider how both types of solution apply to A and B: on both, B is valid. But on one, B has true premises and false conclusion, and contradictories can be false together; on the other (following the Logica Oxoniensis), the counterexample is rejected.
Citation
Read , S 2022 , ' 'Everything true will be false' : Paul of Venice and a Medieval Yablo paradox ' , History and Philosophy of Logic , vol. 43 , no. 4 , 2 , pp. 332-346 . https://doi.org/10.1080/01445340.2022.2040797
Publication
History and Philosophy of Logic
Status
Peer reviewed
ISSN
0144-5340Type
Journal article
Rights
Copyright © 2022 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons. org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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