Judaic logic: A Formal Analysis of Biblical, Talmudic and Rabbinic Logicis an original inquiry into the forms of thought determining Jewish law and belief, from the impartial perspective of a logician[1].

Judaic Logicattemptsto honestly estimate the extent to which the logic employed within Judaism fits into the general norms, and whether it has any contributions to make to them. The author ranges far and wide in Jewish lore, finding clear evidence of both inductive and deductive reasoning in the Torah and other books of the Bible, and analyzing the methodology of the Talmud and other Rabbinic literatureby means of formal toolswhich make possible its objective evaluation with reference to scientific logic. The result is a highly innovative work – incisive and open, free of clichés or manipulation.

Judaic Logicsucceeds in translating vague and confusing interpretative principles and examples into formulas with the clarity and precision of Aristotelean syllogism. Among the positive outcomes, for logic in general, are a thorough listing, analysis and validation of the various forms ofa-fortiori argument, as well as a clarification ofdialectic logic. However, on the negative side, this demystification of Talmudic/Rabbinic modes of thought (hermeneutic and heuristic) reveals most of them to be, contrary to the boasts of orthodox commentators, far from deductive and certain. They are often, legitimately enough, inductive. But they are also often unnatural and arbitrary constructs, supported by unverifiable claims and fallacious techniques.

Many other thought-processes, used but not noticed or discussed by the Rabbis, are identified in this treatise, and subjected to logical review. Various more or less explicit Rabbinic doctrines, which have logical significance, are also examined in it. In particular, this work includes a formal study of theethical logic(deontology) found in Jewish law, to elicit both its universal aspects and its peculiarities.

With regard to Biblical studies, one notable finding is an explicit formulation (which, however, the Rabbis failed to take note of and stress) ofthe principles ofadduction[2]in the Torah, written long before the acknowledgement of these principles in Western philosophy and their assimilation in a developed theory of knowledge. Another surprise is that, in contrast to Midrashic claims, the Tanakh (Jewish Bible) contains a lot more than ten instances ofqal vachomer(a-fortiori) reasoning.

In sum,Judaic Logicelucidates and evaluates the epistemological assumptions which have generated the Halakhah (Jewish religious jurisprudence) and allied doctrines. Traditional justifications, or rationalizations, concerning Judaic law and belief, are carefully dissected and weighed at the level of logical process and structure, without concern for content. This foundational approach, devoid of any critical or supportive bias, clears the way for a timely reassessment of orthodox Judaism (and incidentally, other religious systems, by means of analogies or contrasts).Judaic Logicought, therefore, to be read by all Halakhists, as well as Bible and Talmud scholars and students; and also by everyone interested in the theory, practise and history of logic.


© Copyright Avi Sion,

1995. (Slatkine ed. 1997.)All rights reserved.



[1]Dr. Avi Sion is theauthor ofFuture Logic: Categorical and Conditional Deduction and Induction of the Natural, Temporal, Extensional and Logical Modalities, which is a large-scale study in generic formal logic and epistemology.

[2]The testing, and confirmation or rejection, of hypotheses – i.e. of beliefs, and equally of the reasons or explanations put forward in support of beliefs.