“Rav Moshe makes some additional side points. These may have come from the in person discussions. And then reiterates why he didn’t stop them even though he disagrees with putting up the eruv. His wording is, ‘that it is against what he holds is the law’.”
You again omit that Rav Moshe states that he can’t issue a p’sak din barrur, because he is mechudash.
“1) The assumption is that there is 600,000. One would have to prove that there isn’t. And even if they do, people won’t know about their proofs. And similar considerations.”
You keep on omitting Rav Moshe’s clear words, three million. It is obvious that Rav Moshe’s words are difficult to stomach. Since these numbers would allow an eruv in Brooklyn (and regarding his gezeirah he would allow a section to be demarcated with a tzuras hapesach).
“2) The Rashba about public open places (platya). This could be even if the total population is 600,000. There isn’t a clear precedent for this complication.”
No. As I mentioned previously, Rav Moshe, in the end allows that a platya is reckoned as part a 12 mil by 12 mil area, which would require a population of three million.
“Then Rav Moshe writes that all three reasons are valid even according to what they told him that there are not 600,000 in Brooklyn. Meaning, that there is no way to build an eruv in Brooklyn even if there is not for sure a rsh”r. It simply runs into too many problems that we don’t have a precedent for. So Rav Moshe held not to put up an eruv in Flatbush and avoid the problems. Which is comparable to Yerushalayim.”
No. The only reason not to make an eruv in Brooklyn, according to Rav Moshe, is because he thought there was a population of over three million over 12 mil by 12 mil in Brooklyn. If the numbers are any less than it is a gezeirah, that some may think that it is a reshus harabbim. However, regarding this issue if a tzuras hapesach would encompass a much smaller area in Brooklyn, there is no doubt that he would allow an eruv. Regarding Yerushalayim, as I mentioned, if an eruv was already constructed for Manhattan, Rav Moshe allowed, how much more so regarding Brooklyn, where he was not even sure if it can be compared to Yerushalayim. Moreover, Brooklyn is encompassed by mechitzos, so there is no doubt that Rav Moshe would allow an eruv.