[Avodah] kal vechomer

[Micha Berger]

On Sun, Feb 27, 2011 at 09:37:12AM +0200, Eli Turkel replied to me
:> I am actually happier with the possibility that QvC isn't standard logic.
:> It is listed among middos shehatorah nidreshes bahen, and rules of
:> logic that were well known in Chazal's day -- such as Aristotle's study
:> of syllogisms -- are not. The question of why QvC is derashah and not
:> sevara has bothered me.

...
: However, the gemara does learn halachot from logic. The most famous being
: not killing someone to save one's life because who knows that your blood
: is redder than him.

Yes, "lamah li qera, sevarah hi?" Sevara is used to produce halakhah. But
no other rule of logic is included in any of the lists of derashos.

: On the second question does the gemara learn anywhere the 13 rules of R.
: Yishmael
: (or other opinions) or is this all halacha le-moshe mi-sinai (machloket in
: that?)

They're deOraisa and not in the Torah. You could use one rule of derashah
to derive another, which would give us a deOraisa that is neither written
outright nor halakhah leMosheh miSinai. But it would still mean that at
least one of the derashos would have to be HLMMS (or written in a pasuq
I'm not thinking of) to bootstrap the others.

As for the rules... There isn't really a machloqes. R' Aqiva actually
uses kelal uperat more often than R' Yishmael does -- a point made by
RSRH in the volume of Collected Writings attacking Graetz's position.
What is in dispute is more the organizational system than the contents
themselves.

Tir'u baTov!
-Micha

-- 
Micha Berger             Brains to the lazy
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