© Avi Sion, 2014.
About A Fortiori Argument, in General and in Judaism
Abstract: This paper first details the formal relationships and distinctions between purely a fortiori argument, a crescendo argument (which refers to proportional a fortiori argument), pro rata argument and quantitative analogy. These various forms of argument are often confused, so it is well to clearly describe and explain them. The author then uses these general findings to formally analyze the debate between R. Tarfon and the Sages in Mishna Baba Qama 2:5, in the course of which the important dayo principle is introduced. Thereafter, the author takes a look at the Gemara’s take on this Mishnaic passage (in the Babylonian Talmud, Baba Qama 25a-b).
In late 2013, after three years of intense study, I published a book called A FORTIORI LOGIC: Innovations, History and Assessments (hereinafter, AFL) a novel, 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.
The present paper is a very brief guide to that book, highlighting a few of its salient findings. Although it was largely constructed by means of copy-and-paste from the book, it contains some clarifications not found in the book. It is of course impossible in the 13 or so A4 pages of the present paper to summarize the 700 pages of the original book. I strongly urge readers to study AFL, part 1, regarding formal issues, and AFL, part 2, regarding Jewish matters.