[Avodah] When Early Shabbos is Rosh Chodesh

[Micha Berger]

I want to bring a whole new axis to this conversation. (I know 3 weeks
later is forever in email list time. Sorry!)

I heard RYBS speak at a yarchei kallah in Boston, in August, sometime in
the early 1980s, about bein hashmashos. One bit particularly stuck in
my head because one doesn't expect to hear the expression "multivalent
logic" in the middle of a Yiddish sentence.

Bivalent logic has two levels -- true or false. In a bivalent logic,
the only possible kind of safeiq is one where the state is A or B,
we just happen not to know which.

But the gemara (Kesuvos 14a) calls a family with a chalal problem, but
we aren't sure who a "mishpachas isah", explaining that "'isah' lashon
safeiq hu". "Dough", i.e. a mixture, is a term for safeiq. There are
times where we cannot say the state is A or B because it's both. (And
there are also cases where we cannot limit ourselves to blue or green
because there are items that come in ambiguous shades of aqua. But that
wasn't RYBS's topic.)

Our topic was an esrog that was only used for part of Sukkos. Once it
is qodesh part of the day, it is qodesh and assur behana'ah the rest of
the day, through until tzeis. But, once it is qadosh after sheqi'ah the
next day, it is qadosh all of that day too!

And that was when RYBS declared the concept of date to require multivalent
logic. (IIRC, he said this about safeiq in general. But we don't need
to see whether my memory is accurate for this discussion.)

So maybe we should be distinguishing the laws of bein hashemashos where
we are trying to determine on when one day ends, in contrast to those
where we are trying to determine when the next day begins. And consider
the idea that -- like the case of esrog -- in all these other cases
the safeiq of bein hashmashos makes it part of both days.

Tarta desasrei only comes up when you are arguing that the day both ends
and doesn't end at sheqi'ah, or the next day both begins at tzeis and
began already. (Which is why that esrog isn't assur behanaah forever,
iteratively going to the 3rd day, the 4th day...)

Let's look at the aveilus example (including meat or wine during the
9 days [Ashk] or shavua shechal bo [Seph]): the problem with aveilus
is being mis'abel on Shabbos. So we stop aveilus when Shabbos starts,
even though the previous day ends later than that.

Whereas a ta'anis ends when it ends, not when the next day begins.
So, Asarah beTeiveis (or taanis chalom, or any other hypothetical
taanis) would continue into Shabbos.

Similarly omer has nothing to do with when Shabbos starts, so you can
count during tosefesh Shabbos.

I wonder if this idea can be applied to all our cases.

Tir'u baTov!
-Micha

-- 
Micha Berger                 For those with faith there are no questions.
http://www.aishdas.org/asp   For those who lack faith there are no answers.
Author: Widen Your Tent                        - Rav Yaakov of Radzimin
- https://amzn.to/2JRxnDF