However, if the tzuras hapesach encircled only a neighborhood in Brooklyn, it would be permissible according to Rav Moshe as long as the eruv encompassed fewer than shishim ribo, (ibid., 4:86, 5:28:5, 5:29) [see Does the Eruv Encompass Shishim Ribo] or if Brooklyn was surrounded by mechitzos (ibid., 1:139 the end of anaf 3). [According to Rav Moshe, mechitzos would classify an area as a reshus hayachid d’Oraysa. Therefore, a tzuras hapesach would be sufficient anywhere in an area included by mechitzos; a future post in this series will elaborate on this topic.]
Only when all three criteria have been realized ― that is, Brooklyn has a population of 3,000,000 and the tzuras hapesach encompasses more than shishim ribo and Brooklyn is not enclosed by mechitzos ― would it not be permissible to erect an eruv of tzuras hapesachim even around a section of Brooklyn; dalsos would be needed.
It is important to note that Rav Moshe did not set forth his chiddush as a p’sak for others since his chiddush was not stated in the Achronim and the Aruch HaShulchan did not agree with him. Only when people mistakenly supposed that he was personally supportive of the eruv did Rav Moshe feel a need to clarify that he was not in favor of one, hence his teshuvah clarifying the matter (ibid., 4:87; see Hagaon Rav Moshe Feinstein zt”l’s Reluctance to Pasken Against the Establishment of an Eruv).
Rav Moshe’s personal approach to eruvin prohibited an eruv in Boro Park and Flatbush, because it was based on information that was provided to him at the time.
Brooklyn’s population, including those who commute into the borough to work, is over 3,000,000.
Boro Park and Flatbush independently contain more than shishim ribo.
Brooklyn is not encompassed by mechitzos.
Part 2 of this series will present current Brooklyn facts and statistics that would make the eruv permissible in its present construction even according to Rav Moshe’s personal approach to eruvin.