And Rav Yosef said: In fact we are dealing here with a single alleyway, and Rabbi Shimon and the Rabbis disagree about the same point of dispute between Rabbi Yoḥanan ben Nuri and the Rabbis. As we learned in a mishna: If teruma oil was floating on the surface of wine, and one who immersed during the day, touched the oil, he disqualified only the oil alone. However, he did not disqualify the wine, because it is considered separate from the oil. Only the oil is disqualified, and it does not render other items ritually impure. And Rabbi Yoḥanan ben Nuri says: They are both connected to each other and are considered as one, so the wine is also ritually impure.
The Gemara explains: The opinion of the Rabbis in our mishna is in accordance with the opinion of the Rabbis in the other mishna, who maintain that wine and oil are not connected and therefore cannot be used together in an eiruv, and the opinion of Rabbi Shimon is in accordance with the opinion of Rabbi Yoḥanan ben Nuri, who holds that wine and oil are connected, and may be used together in an eiruv.
תניא רבי אליעזר בן תדאי אומר אחד זה ואחד זה צריכין לערב ואפילו לזה ביין ולזה ביין
It was taught in a baraita:
Rabbi Eliezer ben Taddai says: In both this case, of wine and wine, and that case, of wine and oil, they must establish an eiruv. The Gemara expresses wonder: Did he say this even if the partnership is with this one in wine and also with the other one in wine? Why should these partnerships not be sufficient to consider the items merged?
אמר רבה זה בא בלגינו ושפך וזה בא בלגינו ושפך כולי עלמא לא פליגי דהוי עירוב
Rabba said: If they partnered in the following manner, such that this one came with his wine-filled jug and poured its contents into a barrel, and the other one came with his jug and poured his wine into that same barrel, everyone agrees that it is a valid eiruv, even if they did not act specifically for that purpose.
Where they disagree is in the case where they bought a barrel of wine in partnership. Rabbi Eliezer ben Taddai holds: There is no principle of retroactive clarification, i. e., there is no halakhic assumption that the undetermined halakhic status of items can be retroactively clarified. Consequently, after the wine is consumed, it is not possible to clarify retroactively which portion of the wine belonged to each person. Therefore, they cannot each be said to own a particular part of the wine, which renders it unfit for an eiruv. But the Rabbis hold that there is retroactive clarification, and therefore they may rely on this partnership to establish an eiruv.
Rav Yosef said that this dispute should be understood differently, as Rabbi Eliezer ben Taddai and the Rabbis disagree about whether one may rely on a merging of an alleyway instead of an eiruv, i. e., whether the merging of an alleyway to permit carrying in the alleyway, exempts the courtyards that open into the alleyway from having to establish an eiruv for the purpose of carrying from one courtyard to the other.
דמר סבר אין סומכין ומר סבר סומכין
As one Sage, Rabbi Eliezer ben Taddai, holds that one may not rely on it in that case, as carrying in the courtyards requires specifically an eiruv, and the merging of alleyways is insufficient. And one Sage, i. e., the Rabbis, maintains that one may rely on and use the merging of alleyways to permit carrying between the courtyards as well.
Rav Yosef said: From where do I say this, that this is the subject of their dispute? As Rav Yehuda said that Rav said: The halakha is in accordance with the opinion of Rabbi Meir, which will be detailed later, that one may not rely on a merging of alleyways instead of an eiruv. And Rav Beruna said that Rav said: The halakha is in accordance with the opinion of Rabbi Eliezer ben Taddai, that in both cases they must establish an eiruv. What is the reason he ruled in this manner? Is it not because the rationale for both rulings is one and the same?
אמר ליה אביי ואי חד טעמא תרתי הילכתא למה לי הא קא משמע לן דלא עבדינן כתרי חומרי בעירובין
Abaye said to him: But if it is one reason, why do I need two rulings? On the contrary, it would be enough to rule in one case, from which we could infer the other as well. Rav Yosef replied: There is nevertheless a reason for both rulings, as this comes to teach us that we do not act in accordance with two stringencies of one tanna in matters of eiruv. Had Rav ruled only in accordance with Rabbi Meir, we would have known only that the halakha is in accordance with his opinion with regard to one specific detail of the case. He therefore ruled in accordance with two Sages: Rabbi Eliezer ben Taddai with regard to a merging of alleyways with wine, and Rabbi Meir with regard to a merging of alleyways with bread. Each is stringent with regard to a different detail of the case.
Having mentioned Rabbi Meir, the Gemara now asks: What is the statement of Rabbi Meir, and what is the statement of the Rabbis? As it was taught in the following baraita: One may establish an eiruv with bread between courtyards that open to one another, but if one wanted to establish an eiruv with wine, one may not establish an eiruv in that manner. One may merge the courtyards that open into an alleyway with wine, and if one wanted to establish a merging of alleyways with bread, one may merge the courtyards of alleyways in this manner.
Why does one establish an eiruv between courtyards and also merge the courtyards that open into an alleyway? It is so as not to cause the halakhic category of eiruv to be forgotten by the children, as if a merging of alleyways alone were used, the children would later say: Our fathers never established an eiruv. Therefore, an eiruv is established for educational purposes; this is the statement of Rabbi Meir. And the Rabbis say: One may either establish an eiruv or merge alleyways.
Rabbi Naḥumi and Rabba disagreed about this issue. One of them said: In the case of bread, which may be used both for an eiruv and for a merging of alleyways, everyone agrees that one, either an eiruv or a merging of alleyways, is enough. When they disagree in the case of wine, which may be used only for a merging of alleyways but not for an eiruv, Rabbi Meir maintains that an eiruv is also necessary, while the Rabbis maintain that it is not required.