Terence Parsons

(? - 2022)

John Buridan was the greatest of the medieval logicians. His massive logical text, the Summulae de Dialectica, has been available in a first rate English translation for well over a decade. Now it is joined by his other major logical work, the Treatise on Consequences. The translation provided here runs about a hundred pages. Chapters 1 and 3 concern consequences involving non-modal propositions, and chapters 2 and 4 concern modals. Buridan is a very clear writer, and Read has provided a translation that is both accurate and readable. The book has a helpful introduction.A consequence is a proposition in conditional form such that things cannot be as its antecedent signifies without also being as its..

This entry traces the historical development of the Square of Opposition, a collection of logical relationships traditionally embodied in a square diagram. This body of doctrine provided a foundation for work in logic for over two millenia. For most of this history, logicians assumed that negative particular propositions ("Some S is not P") are vacuously true if their subjects are empty. This validates the logical laws embodied in the diagram, and preserves the doctrine against modern criticisms. Certain additional principles ("contraposition" and "obversion") were sometimes adopted along with the Square, and they genuinely yielded inconsistency. By the nineteenth century an inconsistent set of doctrines was widely adopted. Strawson's 1952 attempt to rehabilitate the Square does not apply to the traditional doctrine; it does salvage the nineteenth century version but at the cost of yielding inferences that lead from truth to falsity when strung together.