[Avodah] chazakah and probability

[Micha Berger]

On Fri, May 21, 2010 at 10:46:53AM +0300, Eli Turkel wrote:
: We have several times discussed if chazakah depends on actual statistics

If it did, wouldn't it be a ruba deleisa leqaman?

I would define a chazaqah disvara as a rule of thumb, a law of nature or
human nature that is "lo daq" and therefore has its rare exceptions.
Thus, it would have to be consistent with statistics, but is stronger
than ruba deleisa leqaman which is entirely the statistic without any
rationale for why it would be true.

: The gemara in Nida brings a chazakah of Raba that a boy/girl at the age of 13/12
: has a chazakah that they have physical simanim needed to be an adult.
...
: The question is why is this chazakah different from other chazakot?

We only rely on this chazaqah for dinim derabbanan, so it's known to be
a weak chazaqah -- the rule has far more exceptions than usual. We rely
on it despite this weakness for tzeni'us reasons, as the alternative is
to have the metzi'us checked.

But we can't invent that qulah for mitzvos de'oraisa. And so, jumping
back in RET's post:
: Nevertheless, SA followed by MA and other poskim state that we do not allow
: a bar mitzvah boy to be motzi others in a Torah law unless we have
: evidence (R Akiva Eger 2 witnesses) that the boy has simanim. Examples
: are parshat zachor, kiddush to be motzi women who have not davened maariv,
: halitza etc.

Note these are de'oraisos. I would also add geir qatan, which is why the
geir qatan can't do a formal qabbalas ol mitzvos before a beis din. It
owuld have to be done within tokh kedai dibur of that 2nd sei'ar ---
a near impossibility.

Although zimun is only a problem if the other two aren't saying the
words themselves. I am under the impression this is why we don't follow
the SA and MA -- our situation is different than that in their pesaqim.

For our kind of zimun, for being sha"tz, for getting an aliyah, we do
rely on the chazaqah. So it's not just that the statistics changed and
the chazaqah evaporated. The statistics were always recognized as being
a small rov, and so the rule of thumb is a poor one. That plus a halachic
desideratum to avoid having to check metzi'us adds up to only being able
to outweigh a derabbanan.

Tir'u baTov!
-Micha

-- 
Micha Berger             It is our choices...that show what we truly are,
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