When not knowing is better than knowing TB Eruvin 44

Today’s daf Eruvin 44 tells when humans can be used as a part of a wall. Today’s discussion begins with the story. “The Gemara relates that Neḥemya, son of Rav Ḥanilai, was once so engrossed in his learning that he did not notice that he was going out beyond his Shabbat limit. Rav Ḥisda said to Rav Naḥman: Your student Neḥemya is in distress, as he is outside the Shabbat limit and cannot enter. What can we do for him?

“Rav Naḥman said to him: Establish a human partition for him, i.e., people who are permitted to go out there should line up and form human walls, through which he is permitted to walk and thereby reenter the Shabbat limit.” (Sefaria.org translation)

After a lengthy discussion the conclusion of the Gemara is that humans can be part of a wall on Shabbat as long as they don’t know that there being used as a wall. The people surrounding Neḥemya, son of Rav Ḥanilai didn’t know that they were being used as a wall even though Rav Ḥisda manipulated them. This is the halakha of making a human wall on Shabbat. (Shulkan Arukh, Orekh Hayyim, 362:5, 7 and 630:12)

Sounds pretty far-fetched to me, but the Gemara actually brings three stories that demonstrates this law. In the first case, members of the wedding party made a human wall with the people knowing they are so being used to a disastrous end for the members of the wedding party. “The Gemara relates that there were these members of a wedding party who engaged the many people present to bring water in on Shabbat from a public domain to a private domain through walls comprised of people who knew that they were being used as partitions for that purpose. Shmuel instructed that they should be flogged. He said with regard to this matter: If the Sages said that a partition is effective when the people act unknowingly, does this mean that they would also say that this is permitted ab initio when they knowingly serve as a partition?” (Sefaria.org translation)

The second story is when a wall enclosure was made around Rava and people took advantage of it, but this trick only worked once. “The Gemara relates that there were once these flasks lying in the market [ristaka] of Meḥoza on Shabbat and could not be moved. When Rava was coming from his discourse accompanied by a throng of people, his attendants brought the flasks into his house, as the crowd of people created human partitions, upon which the attendants capitalized for this purpose. On another Shabbat they wanted to bring them in again, but Rava prohibited them from doing so, reasoning: This is like the case where the people knowingly served as partitions, for presumably the people now knew that they were being used for this purpose, and it is therefore prohibited.” (Sefaria.org translation)

The third story is self-explanatory. “The Gemara further relates that Levi was brought straw through human partitions comprised of people who were unknowingly used for this purpose, and in the same manner Ze’eiri was brought fodder [aspasta], and Rav Shimi bar Ḥiyya was brought water.” (Sefaria.org translation)

The commentators explain why when people know they are being used as a wall on Shabbat is forbidden. Rashi and Rashba make the distinction when people know they’re being used as a wall that wall becomes “permanent” and building a permanent wall on Shabbat is forbidden. When they don’t know they’re being used as a wall, they become a “temporary” wall and this kind of wall is permitted on Shabbat. The Meiri understands the issue completely differently. Using people who know they are being used to build a wall is a forbidden because people will see you treating of the honor of Shabbat lightly, זילזול כבוד השבת, and considered this action as a desecration of the Sabbath.