Our two daf contain pivotal sugyos regarding the laws of partitions and Eruvin.

One of them is a famous dispute between Abaya and Rava regarding a לחי העומד מאליו (a post that was already there prior to it being designated for use in closing off a מבוי.

The classic example is if a part of the one wall sticks out at a 90-degree angle to the wall, forming an effective post.

So long as he had in mind the day before that it should be used as a post for the Eruv, Abaya is of the view that it is acceptable.

On the other hand, Rava is of the view that seeing as it was not placed there specifically to serve as an Eruv pole, it is invalid.

After much back and forth, the Gemara brings a proof that Rav held like the lenient opinion of Abaya, which seems to be conclusive in allowing us to rule in his favor.

It is interesting that although we have a general rule that whenever Abaya and Rava disagree, we follow the ruling of Rava, the Gemara (Bava Metzia 22b ) gives an acronym יעל קגם for 6 cases where we follow Abaya, and Rashi identifies our case, לחי העומד מאליו as one of them.

We should note that at least in the case of our sugya, as well as the sugya quoted above, this is because the Gemara was able to find strong evidence in his favor.

We mentioned in our previous post that the Rambam (Mamrim 1/3) is of the view that things mentioned explicitly in the Torah or passed on orally to Moshe at Sinai are not subject to מחלוקת (debate,) and debates are only find regarding laws based on Chazal’s interpretations of the former through the rules of interpretation or rabbinical decrees and the like.

He also said (ibid 1/4) that even such debates were always settled eventually by the בית דין הגדול (great court or “Sanhedrin” of 71 ordained judges,) and once they were settled, there was no room for halachik debate.

In contrast, once the great court ceased to function, new debates remained essentially unsettled and each sage was free to follow and teach his own view to his students, who would typically follow their Rabbi- the default rule for undecided debates was to be stringent in biblical matters and lenient in rabbinical ones. (Mamrim 1/5)

In reality, this has not been the case, and in Amoraic Bavel where the much-weakened Sanhedrin back in Tiberius had little power, as well as after it ceased to function altogether, later Amoraim have come to conclusions regarding disputes which have thereafter also been regarded as binding.

There have even been rules of thumb formulated, such as following Rav over Shmuel, Rabbi Yochanan over Rav or Shmuel, and Rava over Abaya etc.

The Rambam himself (introduction to M.T.) explains the dictum of רבינא ורב אשי סוף הוראה (Bava Metzia 86a) as meaning that the later Amoraim, Ravina and Rav Ashi, who sealed the Talmud Bavli, essentially had the authority of בית דין הגדול for the last time in history, given that their rulings spread and were accepted by the Jewish people as a whole and all or most of its sages.

Although there is much to discuss and analyse here, it seems clear that a simple understanding of the earlier-quoted Rambam that makes authoritative dispute resolution entirely dependant on בית דין הגדול itself is not sufficient.

In another pivotal dispute, רב פפא, and רב הונא בריה דר’יהושע debate whether פרוץ כעומד (open area equivalent to closed area) is acceptable to consider a side as partitioned off or not.

The general rule is that when מחיצות (partitions) are used to close off a רשות היחיד, gaps of up to 10 אמות are permitted, and considered to be an acceptable פתח (opening) rather than a פירצה (gap)

However, there is an additional requirement recorded in the Mishna on 15b, that there may not be more open space than closed space (in the absence of a צורת הפתח in which case it is more complex.)

The Gemara on this Mishna opens with the above-mentioned debate regarding whether it is sufficient if the closed area is equal to the open area, or whether it needs to be MORE than the open area.

The Gemara seems to understand that the requirement that most of the partition not be open is a הלכה למשה מסיני (law given orally to Moshe at Sinai and passed on via tradition.)- (the precise term used here is “אגמריה רחמנא למשה” which seems pretty self-explanatory!)

It then understands the dispute to be a question of the nature of this הל”מ.

Was it a requirement not to allow most of the partition to be open, or was it a requirement requiring most of the partition to be closed?

Much debate follows onto daf 16 until in a major curveball, the halacha is resolved according to the lenient view, but this seems to be an explicit example of a dispute regarding something passed on explicitly to Moshe at Sinai, a counter-example to the Rambam’s hypothesis limiting such debate to matters involving the rules of interpretation or rabbinic decrees.

Once again, it seems that a simple explanation of the Rambam might not seem feasible and more analysis is required!

These posts are intended to raise issues and stimulate further research and discussion on contemporary topics related to the daf. They are not intended as psak halacha.