Tuesday, July 26, 2011

Kavua Redux II: A Respnse from Prof. Aumann

Prof. Aumann graciously commented on my blog post on his pshat in kavu'a.

I have omitted some parts of his communication that were personal:

Dear Rav Bechhofer, לאי"ט,

Please forgive the long delay in replying to your very good message of 
last week.  For easy reference, the items in this message are numbered.

1. First of all, the short answer to your question is that you got it 100% 
   right.  I have a few comments and elucidations, set out below; but yes, 
   you absolutely did get it right.  Thank you very much for sharing this 
   with your Google group!

2. Thank you for the detailed references regarding קבוע and פריש; they 
   will be a great help.

3. As I recall, Moish Koppel had an explanation involving quantum 
   mechanics; I guess that's what you mean by "indeterminant" or "hybrid."  
   That's pretty airy stuff.

4. The Wikipedia article on moral hazard is good, but I prefer the 
   following definition, which is perhaps a little more focused: We say 
   that a situation with an uncertain outcome is fraught with "moral 
   hazard" if an *interested* party -- one that stands to gain or lose
   from the outcome -- can influence it.
5. Frankly, I don't see any difficulty with the גמרא in זבחים.  The text 
   reads, ניכבשינהו דניידי ונימא כל דפריש מרובא פריש. The literal meaning 
   of this is, "let's force them to move, and then say that every (animal) 
   that gets separated (from the main flock) comes from the majority." 
   That is, one creates a disturbance that makes the whole flock move, and 
   then the animal or animals which get separated from the main flock in 
   the turmoil are considered to come from the majority. This is actually 
   a very elegant way to get a truly random selection, which is indeed not 
   subject to moral hazard, as the *interested* party -- namely the owner 
   of the animals -- is *not* making the selection; the selection is made 
   by the flock itself, when it scatters because of the disturbance. 

   Goldschmidt's translation is "man kann sie ja sich zu bewegen zwingen 
   und sage, was sich trennt, trenne sich von der Merheit," which is 
   exactly the meaning given above. 

   Rashi's גירסא is נכבשינהו דניניידו, which implies that they will move 
   themselves because of a disturbance.  Jastrow (on the word נוד) 
   translates the passage as "let us force them to scatter."

   Rashi's פירוש is יכופו אותם שינודו דלא ליהוי קבוע.  This could be 
   misread to mean that it is sufficient for the whole flock to move as 
   a unit, without scattering. But such a reading would not fit the גמרא 
   itself, which says ונימא כל דפריש מרובא פריש; the word "פריש" implies 
   a separation, like at the bottom of ע"א.

With warmest regards,

Yisrael Aumann


  1. 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?