[Avodah] simple eruv question

[Micha Berger]

On Fri, Nov 13, 2020 at 09:13:58AM -0500, Sholom Simon via Avodah wrote:
> Just an FYI: on Eruvin 94, R Rosner made the following comment...
> What is the lomdus of pi tikra?  Some rishonim say it is just a fancy form
> of gud achis; they put them together, even though the gemara doesn't put
> them together.  Others say, they are different, that maybe it's just a din
> of havdalah.  Meaning: you're not creating any type of structure by pi
> tikra, you're just creating enough to be mavdil the reshuyos, which would
> not be good enough, e.g., for a sukkah, where you need walls

I would have put it this way...

They're clearly different dinim... Pi tiqra is the edge of a roof, a
horizonal surface. Gud achis (and gud achis) are vertical surfaces. Pi
tiqra isn't a "form of" gud achis. The question is whether both dinim
are motivated by the same metahalachic mechanics...

I would think of the question this way:

Gud achis and gud asiq imply a mechitzah. Lekhol hadei'os. Take them
out of the machloqes.

Does pi tiqra also also imply a mechitzah? In which case all three are
different expressions of the same metahalkhah, doing the same thing
working the same way.

Or, is it only providing a well defined edge to the reshus under the roof?
("Havdalah", as R Rosner put it.) And thus different in kind and only
usable for dinim that are about reshuyos.


Sorry, it's too close to Shabbos for a research project to find which
rishonim say what. If someone else doesn't beat me to it, I will try
again after my commitments on Sunday. But I decided to post my current
thoughts now, in hopes someone can fill that part in without needing to
do research.

:-)BBii!
-Micha

-- 
Micha Berger                 None of us will leave this place alive.
http://www.aishdas.org/asp   All that is left to us is
Author: Widen Your Tent      to be as human as possible while we are here.
- https://amzn.to/2JRxnDF          - Anonymous MD, while a Nazi prisoner

:-)BBii!
-Micha

-- 
Micha Berger                 None of us will leave this place alive.
http://www.aishdas.org/asp   All that is left to us is
Author: Widen Your Tent      to be as human as possible while we are here.
- https://amzn.to/2JRxnDF          - Anonymous MD, while a Nazi prisoner