Logic in the Torah

A Thematic Compilation by Avi Sion

Blog posts February 2018

Table of Contents


1.     Logic in the Torah

1.     Introduction

2.     Instances of logic in the Torah

3.     Summary and conclusions

4.     As regards the Tanakh

2.     Adductive Logic in the Torah

1.     The art of knowing

2.     Adduction in Western philosophy…

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The present volume, Logic in the Torah, 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. Logic in the Torah


1.   Introduction

There is evidently quite a bit of logic – inductive as well as deductive – to be found in the Tanakh (the Jewish Bible). Although this document aims, of course, primarily to convey narratives (they did this, they said that) and legislation (do this, don’t do that), it…

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2. Adductive Logic in the Torah


1.   The art of knowing

Induction, as an epistemological concept, refers to the logical processes through which all propositions, and their various constituents, are gradually developed. Some philosophers have tended to define induction as the pursuit of general principles from particu…

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3. Qal vaChomer


1.   Background

Jewish logic has long used and explicitly recognized a form of argument called qal vachomer (meaning, lenient and stringent). According to Genesis Rabbah (92:7, Parashat Miqets), an authoritative Midrashic work, there are ten samples of such of argument in the Tanakh: o…

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4. Revised List of Biblical A Fortiori


1.Problems encountered

We stated earlier that, according to Genesis Rabbah, there are ten cases of a fortiori argument in the Bible: four of them in the Books of Moses and the other six in various other locations. This Midrashic work is traditionally said to have been compiled either by R…

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5. The Language of Biblical A Fortiori


In this essay, my purpose is to analyze the language actually used in Biblical a fortiori statements. An empirical study, without preconceptions.



A Biblical a fortiori argument, as we saw, usually consists of two more or less explicit sentences, one of which is the…

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6. Miriam’s A Fortiori Argument


The a fortiori argument made by Miriam, the sister of Moses, in Numbers 12:14-15, plays an important role in rabbinical discussions relating to such arguments, notably in the Gemara (the commentary on the Mishna). For this reason, I have had to analyze it in considerable detail.


1. …

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7. Louis Jacobs’ Contribution


Rabbinic Thought in the Talmud (2005), by Louis Jacobs, contains an essay devoted to “The Qal Va-Homer Argument in the Old Testament”[1]. We shall here analyze the contributions made in this late essay of his (Jacobs z”l passed away in 2006). Having [before I came across this essay in …

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