Wednesday, November 16, 2016

Kavu'a Again

See these two posts:

I referred to these posts in the course of a chevrusa today. And I found a comment on the latter one that I did not notice previously:

AnonymousSunday, June 30, 2013 10:33:00 AM

Hi, I have used this understanding of Kavua before, it is quite elegant. However how does it fit with the Kavua of the mouse in Pesachim which just came up in Daf Yomi?

This sugya is cited by Prof. Moshe Koppel (cited, in passing, in the second blog post above) in his essay at

The gemara (9b) discusses a scenario where nine piles of matza and one pile of chametz are lying around before Pesach. A mouse comes and takes a piece from one of the piles and enters a house. However, we do not know if it took chametz or matza and thus are in doubt whether the house must be checked once again for chametz. The gemara distinguishes between a case where the mouse is seen taking a piece directly from one of the piles ["kavu'a"] and an instance where the piece snatched by the mouse was first isolated from the piles ["parish"]. These two cases are said to be analogous, respectively, to two cases considered in Ketubot (15a): "If there are nine stores which sell kosher meat and one which sells non-kosher meat and someone took [meat] from one of them but he doesn't know from which one he took, the meat is forbidden. But if [a piece of meat] is found [not in a store], follow the majority." Thus if the majority of stores from which the meat might have originated are kosher, the meat is permitted.

The question is a good question: Where is the "moral hazard" in the case of the mouse?

I think the answer may be found in a word in the Rambam (Chametz u'Matza 2:10). The Rambam does not understand the case as one in which piles are just "lying around." He begins the halacha with the word heini'ach - he placed. 

I would suggest that it is the involvement of the owner of the house that places him in a situation of "moral hazard."

There is another possibility, not as elegant, that this case is different because the owner will be compelled (or not) to redo Bedikas Chametz. Accordingly, his "negi'ah" is his "moral hazard."


  1. If your explanation is correct, and there is moral hazard in this case, then there is also moral hazard in the case in which the mouse took the piece that was parish too.
    And if you tayna, well you can't call it kavua now bc it was already parish and considered mutar, then go back to the original prisha and say that then it was also considered kavua and was never mutar in the first place, because of moral hazard.

    I also find it hard to believe that the case of a mouse taking chametz into your house is considered moral hazard. The possibility is so remote that I wouldn't call that moral hazard.

    I think this discussion is a perfect example of the difference between Telz and Brisk. Brisk would say that such philosophical discussions on kavua is an exercise in futility. Azay is the din.

    Would you please bring this discussion to the attention of Professor Aumann. I would be very curious what he has to say.

    1. I agree that this is the difference between Telshe and Brisk. And that seeking the "philosophical" understanding of kavu'a is a majestic quest. And that the Brisker approach of accepting the tzimtzum is beyond my comprehension. If the case of the mouse is a pircha to Prof. Aumann, then the quest continues. Yishmach lev MEVAKSHEI Hashem!

    2. The response from Prof. Aumann:

      Certainly, I remember our meeting in New Rochelle very well, including the wonderful Shabbat meal at your house. By an amazing coincidence, I have just completed a chibbur on the subject of Kavu'a and Parish, together with my grandson, Shoham Baris, a talmid at the Har Etzion Yeshiva. You will see that we have somewhat widened the moral hazard explanation; it is now simply a matter of choosing versus finding. In particular, the mouse story in Pesachim fits the new paradigm very well, as do all other occurrences of Kavua and Parish in the Shass.

      Attached is a copy of our chibbur. I would be delighted to get comments from you, and in the meantime look forward to reading your blog post.

      With many thanks and best regards, also to your wife,

      Yisrael Aumann

    3. I have not yet looked at the chibbur but have uploaded it to

  2. My own theory, which I've discussed at length (over decades) with R/Dr Koppel, is a R Shimondik treatment of R' Aqiva Eiger's shitah (shu"t 1:136, 141) on the difference between a birur hametzi'us (resolving the doubt) and a rule of hanhagah / birur hadin (behavior when the doubt cannot be resolved). I am repeating mostly because my prior mar'eh maqom was incomplete. (And partly because I think that a shirah of an acharon deserves more attention than it was given, especially when it's among my own pet theories. <grin>)

    1. And so, I would not look at "moral hazard" or at statistics, or (R/Dr Leon Ehrenpreis's chiluq) sets vs classes. Instead, I would look to see whether someone knew the metzi'us, and therefore there was a halachic chalos, or not. If there was, then this is a safeiq in the halakhah. And then we cannot ignore rov -- there is a risk of encountering real danger. Whether that's the owner placing the item, or eidus. Which is why there is no chazaqah bemaqom terei uterei -- at least according to R Aqiva Eiger, the Sheiv Shemaatesa and Rav Shimon, and why terei kemei'ah.

    2. Can you apply this directly to the case of the mouse?

    3. Qavua means that there is an established halakhah, the safeiq is in what that state is. We do not play the odds, because rov is pnly a rule about establishing halakhah.

      The two piles have established pesaqim -- one pile is known chameitz, 9 piles are known matza. If the mouse takes from one of the piles, we saw the crumb starting out in known halachic state, and now we're in a doubt about which state it's in.

      The crumb found on the floor ... We don't know which pile it came from, when we first observe it. The mouse didn't muddy up an existing pesaq / chalos.

    4. ... and everything in the above is how I would apply what R' Aqiva Eiger wrote, and did not require applying my own extrapolations beyond it.

  3. I read Dr. Koppel's article, and while he says his goal is to define kavua in a way that doesn't seem arbitrary, I don't believe he has succeeded.

    The ikar line, in my view is "The critical moment for our purposes is the moment immediately preceding the initial encounter with the piece of meat in question. If this initial encounter occurs while the meat is in the store, the meat is regarded simply as an undistinguished member of a mixed set and its status is thus indeterminate (mechtza al mechtza)."

    This kvius itself seems entirely arbitrary. (Why look at the moment before the initial encounter and not the initial encounter itself?)

    This entire discussion validates what I said last week - that to a Brisker, the Telzer approach of asking "why" leads to a lowering of standards and rigor, wherein svaros such as these are suggested which don't meet the acceptable level of rigor. (see again my comment above on how moral hazard does not explain the case of the mouse.)

    RYGB, any comments?

    1. The passage you cite seems to be a recasting of Reb Shimon's dichotomy between the question of "What" vs. the question of "Why".

      As to the Brisk/Telshe dichotomy, see