Chazal used various hermeneutical rules, such as R' Yishmoel's, to interpret the Torah and to derive novel halachos from it (as well as get support for existing ones).

Can we use those rules nowadays for the same purpose - i.e. to derive novel halachic principles (and not just apply existing principles to new practical situations)? If not, is it because we don't possess some required tradition or knowledge to do so? If that's the case, why wasn't it written down, along with the rest of Oral Tradition?

  • I know that my answer doesn't address " why wasn't it written down, along with the rest of Oral Tradition". First of all, I hate so sound blunt but, it is an "Oral" tradition, after all! Even the Talmud wasn't meant to be written and was done so out of necessity. As to why these rules weren't included in the Bavli or Yerushalmi directly, it's almost impossible to surmise exactly why any particular item was included or excluded. I'm not sure if anyone understands the reasoning. Personally, I would wonder what tractate such rules would fit into.
    – DanF
    May 2, 2019 at 20:34
  • IIRC the intro to Haamek Davar addresses this.
    – msh210
    May 2, 2019 at 23:16
  • Some of rabbi yishma’els
    – Lo ani
    May 3, 2019 at 6:04

1 Answer 1


This article focuses on Rabbi Ishma'el's 13 rules and explains both how they work as well as what current rules are. I'm extracting some items:

The Rabbis checked and limited the force of the Kal Ve- Chomer by applying the principle of Dayyo, i.e., that it is quite suffcient that the law in respect of the thing inferred should be equivalent to that from which it is derived. The origin for this principle is BiblicaL.

The principle of Gezerah Shavah is subject to a number of limitations. Thus we are told, that even though a man may project a Kal Ve-Chomer on his own, no man may advance a Gezerah Shavah unless he has received it as a tradition from his teacher and his teacher from his teacher, all the way back in time to the Lawgiver, Moses.

Most of the other rules apply to specific situations where Torah verses contradict each other or they relate to the order of specifics and generalizations. I couldn't locate anything in the article that states if one can devise his own analogies. However, in viewing the examples and seeing how complex it is to apply these rules in most situations, I'm humbled by how difficult it is to analyze it and arrive at one's own conclusions.

  • And yet probably most of the details of the 613 mitzvos are derived using these rules (kal vachomer, gezeira shava, repetitions of words, etc.), by the various halachic midrashim (e.g. Sifra, Sifre). [See myjewishlearning.com/article/sifra-and-sifre ]. So we see that the rules were employed quite ubiquitously and routinely during the time of Chazal. However their use seems to have suddenly dropped off after that time (did any Geonim use them? Rishonim? Certainly not anything from recent times). Therefore I was wondering what happened - what prevented later generations?
    – user9806
    May 2, 2019 at 22:28
  • It seems that most legal derivations nowadays take the form of either 1) applying already established halachos/principles [which were derived by Chazal using exegesis/hermeneutics] to new situations (e.g. electricity on Shabbos, etc.), or 2) Appeal to earlier authorities, inferring their intent and/or taking a majority vote (as e.g. the Shulchan Aruch with Rif,Rosh and Rambam). But none of that has the power of deriving truly new laws from the Torah itself, which would then take on an independent deoraysa status.
    – user9806
    May 2, 2019 at 22:41

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