Logic in the Talmud

A Thematic Compilation by Avi Sion

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Blog posts March 2018

Table of Contents


1.         A Fortiori in the Talmud

1.         Brief history of a fortiori

2.         A brief course in the relevant logic

3.         A fresh analysis of Mishna Baba Qama 2:5

4.         A logician’s reading of Numbers 12:14-15

5.  …

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The present volume, Logic in the Talmud, is a ‘thematic compilation’; that is, it is a collection of essays previously published in some of my primary works. Such collections allow me to increase the visibility of scattered writings over many years on a specific subject. In the present case,…

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1. A Fortiori in the Talmud


1.   Brief history of a fortiori

There is credible written evidence that a fortiori argument was in use in very early times thanks to the Jewish Bible. Five instances are apparent in the Torah proper (the Five Books of Moses, or Pentateuch) and about forty more are scattered throughout …

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2. More on A Fortiori in the Talmud

The present chapter is a continuation of the preceding, aimed at further clarifying some details.


1.   Natural, conventional or revealed?

Our above critique of the Gemara was based to some extent on the assumption that it considers dayo as a principle, which the Sages regard as a har…

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3. Enumeration of A Fortiori Discourse


1.   A fortiori discourse in the Mishna

If we wish to enumerate the use of a fortiori argument in the Talmud, we must first make a census of its use in the Mishna (closed ca. 200 CE) – and perhaps also the Tosefta (closed ca. 300 CE), if any – since the Mishna is a document found in bot…

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4. Post-Talmudic Commentaries


1.   Logic and history issues

In the present chapter, our object shall be to discuss and to some extent trace some of the developments in rabbinic and more broadly Jewish thought concerning the a fortiori argument, and to a lesser extent more broadly the hermeneutic principles. This is …

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5. A Fortiori in Certain Lexicons

In the present chapter, we shall investigate the treatment (or non-treatment) of a fortiori argument in general – and of the more specifically Jewish concepts of qal vachomer and dayo – in three standard encyclopedias (more are dealt with in AFL 32). This is not intended to be an exhaustive survey…

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6. Initial Impressions on Method

In this chapter, we shall make some preliminary, general comparisons between some of the propositional forms and logical processes used in Biblical, Talmudic and Rabbinic literature, and those found in modern, secular scientific thought[1].

But note well that these initial reflections were writ…

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7. Traditional Teachings

A brief overview of the ways Judaism traditionally presents the art of “Talmud Torah”, followed by some suggestions on same.


1.   Hermeneutics

Talmudic law was decided, with reference to the Torah, after much debate. In a first stage, the debate crystallized as the Mishnah; in a …

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8. The Thirteen Midot

In the present chapter, we shall indulge in a closer scrutiny and frank criticism of Talmudic/Rabbinic hermeneutics.


1.Exposition and evaluation

Traditional presentations of the principles and practice of Rabbinic exegesis consist in listing the Thirteen Midot of R. Ishmael (at least, …

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9. The Sinai Connection


We shall now look into the issue of the Sinaitic origin of Talmudic/Rabbinic hermeneutics.


1.Verdict on rabbinic hermeneutics

I have no doubt that certain doctrinaire defenders of Judaism will be very upset with me for the devastating deconstruction of Rabbinic hermeneutics in th…

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Main References


Abitbol, Gabriel.  Logique du droit talmudique.  Paris: Sciences Hébraïques, 1993.

Aristotle.  The Works of Aristotle.  Ed. William David Ross.  Chicago: Encyclopædia Britannica, 1952.

Avraham, Michael.  “The ‘Kal Vachomer’ as a Syllogism – Arithmetic Model” (in Hebrew).  In: …

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