[Avodah] Halacha as a System and Deriving halachah for new situations (two subjects for the price of one!)

[David Riceman via Avodah]

I wanted to reply to this in more detail, but after a while I couldn't
see the forest for the trees. So here's the forest:

RJR offered three alternatives, none of which I think is tenable.

1. Halacha is a single unified ideal.

This can't be true for several reasons. Drashos HaRan #7 rejects it
because it's inconsistant with aharei rabbim l'hatos. His solution is
to postulate a non-ideal halachic system which he calls halacha l'fi
ha'sechel ha'enoshi.

In addition I pointed out that there's a double layer of decision: voting
about law is based on case law, but halacha is conceptualized based on
rubrics. Arrow's theorem ought to imply that there is no unified ideal.

RMB identified this opinion with the Rambam. This also can't be true.
See MN III:26 (tr. Schwartz p. 514) that while mitzvos have reasons,
the details of mitzvos do not, and God determined them arbitrarily.
This can't be an "ideal" system.

2a. Halacha is a "chronologically monotonic historical process" determined
by God.

This also can't be true. There are innumerable cases where later rishonim
reject the opinions of earlier rishonim or even geonim because they
conflict with the later rishon's construal of the gemara. It still
happens, though my impression is less frequently, among aharonim.
Certainly the biur haGra on SA does this occasionally.

RMB associates this opinion with "Rashi, Ritva, Ran, and any other rishon
we've discussed in dozens of prior iterations, except the Rambam".
Again this can't be true because all of these reject some of their
predecessors' opinions based on their reading of Hazal.

2b. Halacha is a "chronologically monotonic historical process" determined
"because the rabbis determined this to be how an effective legal system
must work".

I've already rejected monotonicity. I don't know of anyone, Hazal or
rishon, who says that this is "how an effective legal system must work".
It's true that the Ramban, in the introduction to Milhamos HaShem, says
that deference to our teachers imply that we should accept precedent
in cases where we are uncertain, but there are plenty of examples, even
in MH, that he rejects the opinion of the Rif. And I know of no one who
attributed this opinion to God.

I wanted to write more on the case of tannur shel achnai. Maybe soon.

David Riceman