[Avodah] : kosher switch

[Chana Luntz]

I wrote:
> : Why?  If at any given point, you still have only a 50% chance of
> getting a
> : head?

And RMB replied:

> If brushing one's hair is pesiq reishei for pulling hairs out, it's
> not because we consider the odds of uprooting each hair as a separate
> risk.
> 
> AIUI, the odds add up.

But with regards to hairs, this is in space, while in the case of the kosher
switch, the odds you are adding up are in time.

Interestingly, in http://www.aishdas.org/avodah/vol28/v28n136.shtml#14 I
asked why was it that in the case of using breira to all for terumah, Rabbi
Meir was not choshesh for the wine cask breaking on shabbas, given that his
is the shita of bein chayish l'miuta.  And an answer that was sent to me
privately was that in each case where Rabbi Meir was chayish l'miuta the
question is whether the person or the object currently belongs to the
majority class or the minority class, Nowhere, though, do we find R. Meir
saying that we must be concerned lest something which is a minority
likelihood may occur to the person or object under consideration.

In other words, R' Meir is chayish l'miuta in space, but not in time.
Similarly it seems to me, the psik reish of pulling hairs out is about
space, that at least one of the hairs currently in existence and being
brushed will inevitably fall out, and that this is fundamentally different
to a series of cumulative acts in time.

> : > IOW, I don't think being goreim something that rov of the
> : > time violates an issur is any more mutar than geramah of a vadai.
> :
> : Well clearly there is such a concept - that is precisely the din of
> psik
> : resha....
> 
> Only if pesiq reishei requires specifically a vadai, and not a ruba
> deruba. Which is a rephrase of my earlier statement. How do you know
> that?

Actually I myself don't think it matters whether it is a vadai or ruba
deruba.  I was just noting that the language of the  gemora itself assumes
we are talking about a vadai here - ie "will it not die?" not in the vast,
overwhelming number of cases it will die.  On the other hand, I was pointing
out that the reality of Mike the Headless Chicken might be used to say that
in practice psik reisha is not just vadai, but also ruba deruba, despite the
language of the gemora.

But regardless whether psik reisha is vadai or ruba d'ruba, the case being
discussed as the paradigms of psik resha are talking only about a one time
acts, not a series of acts spread out over time that culminate in an almost
certain result.  After all, vadai every single chicken alive at the time of
Chazal is now dead, due to the passage of time.  But that was not the psik
reisha Chazal were talking about. 

The fact that every definition of grama has some element of time delay
(grama is not merely a shinui) shows again that time is different from space
and you cannot necessarily add up little time units in the way you may be
able to with space units.

> ...
> : The reality is that if this is your only option, you put up with
> things not
> : working on shabbas as smoothly as they do on weekdays...
> 
> But it must work with enough reliability for my "sure enough" standard
> to be met.

Yes, agreed.

> Tir'u baTov!
> -Micha

Regards

Chana