Rav Shach in laws of damage 13 law 19 ,Gemara Bava Kama page 6a.

Now I have been looking at Rav Shach in laws of damage 13 law 19 and he points to the Gemara Bava Kama page 6a. From there I found an answer to the question that many achronim including Rav Shach bring on the Rambam. There we see twice that there can be a reason to think that if he still owns the stone, knife or package or the tree or wall that fell into a public domain, there is more of a reason to make him not obligated. And beside that I can see the reason behind it. If he still owns it, then he intends to pick it up, and if it causes damage before he got a chance to pick it up, then he should be not liable since it is not his fault. This exact reason we find on page 22 Bava Kama where there was a wall that fell down and fire escaped and did damage, and the owner of the fire did not have a chance yet to repair the wall. He is not liable because it is not his fault (since he did not have a chance to repair it yet). But if he abandoned the piece or hard in the public domain there is more of a reason to make him liable since he intends to leave the damaging objects there, and he never intends to remove them. Okay. Now that I have said this let me bring the gemara. It says abaye said the mishna come include his stone, knife or package that he put on a roof, and they fell due to a common wind. The Gemara asked on this that if he abandoned them in the public domain that is a regular case of digging a pit in a public domain. so instead the gemara suggests that since that is too obvious, then it must be that the mishna is coming to include when he did not abandon them. At this point, in the Gemara we see that there is more of a reason to a make him not liable when still own the stone or knife because we need to mishna to include them. This same idea is repeated on page 6b where Ravina said the mishna is coming to tell us about a wall or tree that fell into a public domain, that they are liable. if he abandoned them, then it is obvious, and there is no reason for the mishna to tell us that. so rather the case is when he did not abandon them, and there we might think he is not obligated. so, we need the mishna to tell us that he is liable. Therefore, here also we see there is a more of a reason to make him not liable when he still owns the tree and wall. That is why you need to Mishna to come and include it. This is all coming to answer this question. The Rambam writes that if a wall or tree fell into a public domain, he is not liable even though he abandoned them. Usually, you say such and such is the case even though there is such and such a reason that militates against it. so here the Rambam is saying that he is not liable even though there is this reason that militates against it. That reason is he abandoned them. But if he abandoned them that would seem to be more of reason to make him not liable. So, the answer is what I wrote up above. If he abandoned them, he should be liable since he intends to leave them in the public domain. But even so, he is not liable. However, I want to bring here how Rav Shach answers this question on the Rambam. He says that the meaning is that the owner of the pit abandoned his domain where the pit is located, and thus that area becomes a public domain and we already know that a pit is liable only in a public domain, so even though he abandoned the pit and that area still he is not liable unless there was warning by the court. If there was warning by the court to remove the wall and tree and more than 30 days have passed, then he is liable. This answer is clear. However, I still have a question on the end of that chapter in Rav Shach H say at the end that the reason the Rambam did not bring the law of Abaye that if he brought his tone knife or package to a roof top and they fell, that he is liable because it is a “all the more so” that can easily be derived from the case of the wall and tree that fell. To me this seems hard to understand because the Rambam say that the wall and tree are not liable. So, you can not learn liability to another case from them unless that other case would also have the court warning him and there were more than thirty days have passed. But we never heard of these conditions in the case of Abaye Furthermore, there is another question I have on this answer of Rav Shach. {His answer is that once we know the law about the wall and tree that fell, then we can know about the stone on the rooftop. The question I have is this. Abaye says we learn liability of the stone on the rooftop from the common denominator between pit and fire. For you might have said that the stone knife and package on the roof should not be liable because there is another force acting on them beside the owner’s force, that is the wind. Well, we can answer that objection from fire. For just like fire is obligated even though another force is acting on it, so the stone and knife on the roof also are liable. Now ho could we know this from the case of the wall and tree that fell? For in that case, Ravina said we know they are liable because of pit and ox. For you might have said that maybe they should not be liable because they were not made from the beginning to do damage, well we can answer that because ox also was not made from the beginning to do damage, and yet it is liable. so too should the tree and wall that fell be liable. But if we would know all this, how could we learn to a case where another force is acting on the thing that causes damage? maybe that would be not liable until we learn it from somewhere. so, I have a hard time understanding this answer of Rav Shach ______________________________________________________________Now I have been looking at רב שך in הלכות ניזקי ממון י''ג הלכה י''טand he points to the גמרא בבא קמא page ו' ע''א. From there I found an answer to the question that רב שך bring on the רמב''ם. There we see twice that there can be a reason to think that if he still owns the stone, knife or package or the tree or wall that fell into a public domain AND CAUED DAMAGE, there is more of a reason to make him not obligated. And beside that I can see the reason behind it. If he still owns it, then he intends to pick it up, and if it causes damage before he got a chance to pick it up, then he should be not liable since it is not his fault. This exact reason we find on page כ''ב בבא קמא where there was a wall that fell down and fire escaped and did damage, and the owner of the fire did not have a chance yet to repair the wall. He is not liable because it is not his fault (since he did not have a chance to repair it yet). But if he abandoned the shards in the public domain there is more of a reason to make him liable since he intends to leave the damaging objects there, and he never intends to remove them. Okay. Now that I have said this let me bring the גמרא. It says אביי said theמשנה come include his stone, knife or package that he put on a roof, and they fell due to a common wind. The גמרא asked on this that if he abandoned them in the public domain that is a regular case of digging a pit in a public domain. so instead the גמרא suggests that since that is too obvious, then it must be that theמשנה is coming to include when he did not abandon them. At this point, in the גמרא we see that there is more of a reason to a make him not liable when still own the stone or knife because we need toמשנה to include them. This same idea is repeated on page ו' ע''א where רבינא said theמשנה is coming to tell us about a wall or tree that fell into a public domain, that they are liable. if he abandoned them, then it is obvious, and there is no reason for theמשנה to tell us that. so rather the case is when he did not abandon them, and there we might think he is not obligated. so, we need theמשנה to tell us that he is liable. Therefore, here also we see there is a more of a reason to make him not liable when he still owns the tree and wall. That is why you need toמשנה to come and include it. This is all coming to answer this question. ר''מ writes that if a wall or tree fell into a public domain, he is not liable even though he abandoned them. Usually, you say such and such is the case even though there is such and such a reason that militates against it. so here ר''מ is saying that he is not liable even though there is this reason that militates against it. That reason is he abandoned them. But if he abandoned them that would seem to be more of reason to make him not liable. So, the answer is what I wrote up above. If he abandoned them, he should be liable since he intends to leave them in the public domain. But even so, he is not liable________________________ However, I want to bring here how רב שך answers this question on the ר’’מ. He says that the meaning is that the owner of the pit abandoned his domain where the pit is located, and thus that area becomes a public domain and we already know that a pit is liable only in a public domain, so even though he abandoned the pit and that area still he is not liable unless there was warning by the court. If there was warning by the court to remove the wall and tree and more than thirty days have passed, then he is liable. This answer is clear. However, I still have a question on the end of that chapter in רב שךTHERE HE say that the reason the ר’’מ did not bring the law of אביי that if he brought his stone, knife or package to a roof top and they fell by a common wind, that he is liable because it is a “all the more so” that can easily be derived from the case of the wall and tree that fell. To me this seems hard to understand because the ר’’מ say that the wall and tree are not liable. So, you can not learn liability to another case from them unless that other case would also have the court warning him and there were more than thirty days have passed. But we never heard of these conditions in the case of אביי Furthermore, there is another question I have on this answer of רב שך . {His answer is that once we know the law about the wall and tree that fell, then we can know about the stone on the rooftop. The question I have is this. אביי says we learn liability of the stone on the rooftop from the common denominator between pit and fire. For you might have said that the stone knife and package on the roof should not be liable because there is another force acting on them beside the owner’s force, that is the wind. Well, we can answer that objection from fire. For just like fire is obligated even though another force is acting on it, so the stone and knife on the roof also are liable. Now ho could we know this from the case of the wall and tree that fell? For in that case, רבינא said we know they are liable because of pit and ox. For you might have said that maybe they should not be liable because they were not made from the beginning to do damage, well we can answer that because ox also was not made from the beginning to do damage, and yet it is liable. so too should the tree and wall that fell be liable. But if we would know all this, how could we learn to a case where another force is acting on the thing that causes damage? maybe that would be not liable until we learn it from somewhere. so, I have a hard time understanding this answer of רב שך