When is an alleyway not an alleyway? TB Eruvin 74

Today’s daf TB Eruvin 74 provides us with three different definitions what qualifies for an alleyway (מבוי). “Rav said: An alleyway cannot become permitted for carrying through a side post (לח) and a cross beam (קורה) unless there are houses and courtyards opening into it. This formulation implies that there must be at least two courtyards, each of which contains at least two houses. In the absence of these conditions, however, it is not considered an alleyway that can be permitted by means of a side post or a cross beam. And Shmuel said: Even one house without a courtyard and one courtyard with just one house is enough. And Rabbi Yoḥanan said: Even a ruin and a courtyard with a house suffice for a side post or a cross beam to render carrying in an alleyway permitted.” (Sefaria.org translation)

Rav’s position is the most stringent and Rabbi Yoḥanan’s position is the most lenient with Shmuel’s position in the middle. An exacting reading of the Mishnah support’s Rav’s position that an alleyway needs at least two courtyards opening into it with two houses in each courtyard. “With regard to the halakhot of eiruv, we have only the wording of our mishna. The mishna states that an alleyway is to its courtyards (the word courtyards is in the plural and the minimum number of courtyards would have to be two-gg) like a courtyard is to its houses (the word houses is in the plural and the minimum number of houses would have to be two-gg), which indicates that an alleyway must have at least two courtyards in order to be considered an alleyway and be rendered permitted for carrying through a side post or cross beam.”

The halakhic definition of an alleyway follows Rav’s understanding. The Mishnah Berurah[1] provides the underpinning reason of Rav’s position. Any place where homeowners would live and do things privately there like eating, needs a more visible wall to enclose it as a private domain. Since people don’t use alleyways for private purposes only a side post or a crossbeam is necessary to symbolically close it. This leniency only applies if the alleyway is less than 10 amot wide.[2] (Shulkhan Arukh, Orekf Hayyim 363, Berurah Mishnah, Note 13) To generate the necessary “public“ foot traffic in the alleyway, it needs at least two courtyards with two houses in each courtyard.

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[1]Mishnah Berurah is a work of halakha (Jewish law) by Rabbi Yisrael Meir Kagan (Poland, 1838–1933, also known Mishnah Berurah Mishnah Berurah as Chofetz Chaim). It is a commentary on Orach Chayim, the first section of the Shulchan Aruch which deals with laws of prayer, synagogue, Shabbat and holidays, summarizing the opinions of the Acharonim (post-Medieval rabbinic authorities) on that work. (https://en.wikipedia.org/wiki/Mishnah_Berurah)

[2] - ואף דבחצר בעינן דוקא פס רחב ד' טפחים הכא הקילו חכמים והטעם שכל שהוא עשוי יותר לדירה ולתשמישי הצנע צריך מחיצות יותר גמורות ולפיכך החצרות שדרכן של בעלי בתים להשתמש בהן יותר בתשמישי הצנע ולאכול צריכות מחיצותיהן להיות יותר גמורות שיהיה שם רה"י עליהן מהמבואות שאין משתמשין בהן בתשמישי הצנע ולפיכך די במבוי בלחי ועיין לקמן סכ"ו שזהו דוקא כשאין רחב פתחו יותר מעשר אמות ועוד פרטים עי"ש