Daf 68 (Shabbas 5a-5b)
Summary. Since a public domain with a roof “does not resemble the encampment of the Israelites in the wilderness,” moving something four amos within it does not incur liability. If the object is thrown, the one who threw it is liable if the catcher can receive it standing in place; the catcher is liable if he must run toward it to catch it.
Is the interior of a basket held in a public domain public or private? (The question, ArtScroll suggests, is answered one way here and another way on 101a.) The rabbis are clearly puzzled by the mishnah: does it deal with a midget? Rava rejects the possibility that it deals with a midget; one should not use unlikely examples to explain general rules. Even so, R’Yochannan then inquires, “If someone threw an object and he himself left his place and caught it, what is the law?” The question remains unanswered. Rava then asks, “If a nut is in a vessel and the vessel is floating upon water, do we follow the nut (which is at rest in the vessel) or the vessel (which is not at rest)?” This, too, remains unanswered.
When I first encountered the public domain with a roof, I thought of the shopping mall. If indeed moving an object within it does not incur liability then the question of shopping is reduced to whether or not it is permissible to use money on Shabbat. On 5B we have a baraisa that begins, “If someone transfers an object from a store to a public plaza . . .” As there is no mention of a transaction, there is still no clarity on exchanging funds. However, new technology would snese the iPhone in my pocket and capture my account information. Is it considered “carrying” to have the iPhone in my pocket? Of course, there is still the question of how to transfer the merchandise to my car. Even if the parking is under the same roof as the mall stores, the car is itself a private domain. Perhaps if my wife sits in the car without the intention of receiving the package I may reach into the private domain with the package in hand– but, no, in that case my intention would make me liable. And, in any event, I can’t move the car– or can I? Can I move a private domain within a public domain (at least within the boundaries of an eruv)? If I am not carrying anything and I go into the private domain surrounded by the public domain . . .