Terence Parsons – författare

Terence Parsons presents a lively and controversial study of philosophical questions about identity. Is a person identical with that person's body? If a ship has all its parts replaced, is the resulting ship identical with the original ship? If the discarded parts are reassembled, is the newly assembled ship identical with the original ship? Because these puzzles remain unsolved, some people believe that they are questions that have no answers, perhaps because the questions are improperly formulated; they believe that there is a problem with the language used to formulate them. Parsons explores a different possibility: that such puzzles lack answers because of the way the world is (or because of the way the world is not); there is genuine indeterminacy of identity in the world. He articulates such a view in detail and defends it from a host of criticisms that have been levelled against the very possibility of indeterminacy in identity.

For nearly four centuries, when logic was the heart of what we now call the 'undergraduate curriculum', Peter of Spain's Summaries of Logic (c. 1230) was the basis for teaching that subject. Because Peter's students were teenagers, he wrote simply and organized his book carefully. Since no book about logic was read by more people until the twentieth century, the Summaries has extensively and profoundly influenced the distinctly Western way of speaking formally and writing formal prose by constructing well-formed sentences, making valid arguments, and refuting and defending arguments in debate. Some books, like the Authorized Version of the English Bible and the collected plays of Shakespeare, have been more influential in the Anglophone world than Peter's Summaries--but not many. This new English translation, based on an update of the Latin text of Lambertus De Rijk, comes with an extensive introduction that deals with authorship, dating, and the place of the Summaries in the development of logic, before providing a chapter-by-chapter analysis of Peter's book, followed by an analysis of his system from the point of view of modern logic. The Latin text is presented on facing pages with the English translation, accompanied by notes, and the book includes a full bibliography.

Terence Parsons presents a new study of the development and logical complexity of medieval logic. Basic principles of logic were used by Aristotle to prove conversion principles and reduce syllogisms. Medieval logicians expanded Aristotle's notation in several ways, such as quantifying predicate terms, as in 'No donkey is every animal', and allowing singular terms to appear in predicate position, as in 'Not every donkey is Brownie'; with the enlarged notation come additional logical principles. The resulting system of logic is able to deal with relational expressions, as in De Morgan's puzzles about heads of horses. A crucial issue is a mechanism for dealing with anaphoric pronouns, as in 'Every woman loves her mother'. Parsons illuminates the ways in which medieval logic is as rich as contemporary first-order symbolic logic, though its full potential was not envisaged at the time. Along the way, he provides a detailed exposition and examination of the theory of modes of common personal supposition, and the useful principles of logic included with it. An appendix discusses the artificial signs introduced in the fifteenth century to alter quantifier scope.