Much of today’s daf revolves around the general rule that an opening in a wall of an alley must be less than 10 cubits in order to carry within it on Shabbat. Anything more than 10 cubits requires an eruv.
The Gemara’s discussion feels a bit like an elementary geometry class, focusing on the particulars of what sorts of partitions are complete enough to permit carrying within them on Shabbat. For example, if a wall has many doors and windows that amount to a greater area than the solid wall itself, does that wall count as a wall for the purposes of carrying within it on Shabbat?
The Gemara interrogates this question further through this story:
Ravin bar Rav Adda said that Rabbi Yitzḥak said: There was an incident involving a person from the valley of Beit Ḥortan who stuck four poles into the ground in the four corners of his field, and stretched a vine over them, creating the form of a doorway on each side. He intended to seal the area so that he would be permitted to plant a vineyard in close proximity without creating a forbidden mixture of diverse kinds in a vineyard. And the case came before the Sages, and they permitted him to consider it sealed with regard to diverse kinds.
The term “diverse kinds” refers to the biblical prohibition known as kilayim (כלאים) — pronounced kill-AHH-yim — which bars various agricultural practices that involve the mixing of diverse species. In the case above, the farmer from Beit Hortan was trying to respect the prohibition on planting certain types of crops in a vineyard. To create a separation between the vines and the crops, he erects four poles and stretches a vine over them.
Since the sages considered the symbolic doorway created by the vine to be a sufficient barrier to permit the planting of diverse kinds, Reish Lakish concludes it’s also sufficient for a symbolic boundary to seal an alleyway for carrying on Shabbat. But Rabbi Yohanan disagrees, arguing that the vineyard precedent does not apply to Shabbat.
Later on the daf, Rabbi Yohanan relates a different version of the story.
Rabbi Yoḥanan said to Reish Lakish: That is not the way that the incident transpired.
As Rabbi Yehoshua went to Rabbi Yoḥanan ben Nuri to study Torah, even though Rabbi Yehoshua himself was an expert in the halachot of diverse kinds and found him sitting among the trees, and Rabbi Yehoshua stretched a vine from one tree to another and said to him: Rabbi, if there are grapevines here, in the enclosed area, what is the halacha with regard to sowing diverse kinds of seeds here, on the other side of the partition?
Rabbi Yoḥanan ben Nuri said to him: In a case where the trees are only ten cubits apart, it is permitted; however, where they are more than ten cubits apart, it is prohibited.
In Rabbi Yohanan’s version of the story, the viability of a vine for the purposes of marking off a vineyard from the rest of a farm applies only where the overall opening is ten cubits apart. Anything larger, and the vine would not suffice. The crucial issue here is the width of the opening one is trying to symbolically mark, not the particular way one chooses to mark it.
But there’s a larger lesson in the second story too. Though Rabbi Yehoshua is a legitimate expert in the laws of kilayim, he still consults another leader who seems to have a kind of lived experience of the subject. This makes perfect sense against the backdrop of the wider discussion on what’s missing from walls, doors, and windows.
Here we can learn a model of how to disagree, even fundamentally: confront your own biases, consult with the opinions of others, and check with what’s out there in the real world.