Eruvin 8 - Sea on one side and garbage heap on the other
There was on an alley with courtyards, which on one side faced the sea, while on the other it was fenced by a garbage heap. The garbage made a fence going up, and the sea wall was a fence going down, so it should have been permitted to carry in this alley, but Rabbi Yehudah the Prince would neither permit nor prohibit carrying there. Why? He did not want to prohibit, because after all it had partitions on both sides; he did not want to permit, because the garbage heap might eventually be removed, while the sea might be made shallow with sand, thus obliterating the partitions and making it in the future forbidden to carry.
But why should such future considerations be taken into account? Because it is possible that one will decide to remove the garbage. And, this is a concern only the case of an individual, but if the garbage is communal, then carrying is allowed - because it is very rare that a communal garbage heap will be moved with mutual agreement.
Art: Paul Signac - Sandy Seashore
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