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Last edited by Avi Sion
March 2, 2017 | History

A Fortiori Logic: Innovations, History and Assessments 1 editions

Cover of: A Fortiori Logic | Avi Sion
About the Book

A FORTIORI LOGIC: INNOVATIONS, HISTORY AND ASSESSMENTS, by Avi Sion, is a wide-ranging and in-depth study of a fortiori reasoning, comprising a great many new theoretical insights into such argument, a history of its use and discussion from antiquity to the present day, and critical analyses of the main attempts at its elucidation. Its purpose is nothing less than to lay the foundations for a new branch of logic, and greatly develop it; and thus to once and for all dispel the many fallacious ideas circulating regarding the nature of a fortiori reasoning.


The work is divided into three parts.

The first part, Formalities, presents the author’s largely original theory of a fortiori argument, in all its forms and varieties. Its four (or eight) principal moods are analyzed in great detail and formally validated, and secondary moods are derived from them. A crescendo argument is distinguished from purely a fortiori argument, and similarly analyzed and validated. These argument forms are clearly distinguished from the pro rata and analogical forms of argument. Moreover, we examine the wide range of a fortiori argument; the possibilities of quantifying it; the formal interrelationships of its various moods; and their relationships to syllogistic and analogical reasoning. Although a fortiori argument is shown to be deductive, inductive forms of it are acknowledged and explained.

The second part of the work, Ancient and Medieval History, looks into use and discussion of a fortiori argument in Greece and Rome, in the Talmud, among post-Talmudic rabbis, and in Christian, Moslem, Chinese and Indian sources. Aristotle’s approach to a fortiori argument is described and evaluated. There is a thorough analysis of the Mishnaic qal vachomer argument, and a reassessment of the dayo principle relating to it, as well as of the Gemara’s later take on these topics. Lists are drawn up of the use of a fortiori argument in Jewish Bible, Mishna, the works of Plato and Aristotle, Christian Bible and Koran; and the specific moods used are identified.

The third part of the present work, Modern and Contemporary Authors, describes and evaluates the work of numerous (some thirty) recent contributors to a fortiori logic, as well as the articles on the subject in certain lexicons.

This book also contains, in a final appendix, some valuable contributions to general logic, including new analyses of symbolization and axiomatization, existential import, the tetralemma, the Liar paradox and the Russell paradox.
added by Avi Sion. "Abstract"

1 edition First published in 2013

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Cover of: A Fortiori Logic
2013, Avi Sion /
A Fortiori Logic
Paperback in English


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March 2, 2017 Edited by Avi Sion added description
March 2, 2017 Edited by Avi Sion added description
December 12, 2013 Edited by Avi Sion Edited without comment.
December 12, 2013 Edited by Avi Sion added description
December 10, 2013 Created by Avi Sion Added new book.