We are now beginning the tenth chapter of Tractate Bava Metzia, which introduces a completely new topic. This chapter, together with the first two chapters of Bava Basra, deals with the laws of neighbors - the real estate laws that apply to neighbors whose plots of land or residential homes are adjacent to one another.
The division seems puzzling, and the reason for it is rooted in the fact that originally, Bava Metzia was part of one large tractate - Tractate Nezikin, which contained thirty chapters. The tractate was divided somewhat arbitrarily into three units of ten chapters each, and the meaning of the word 'bava' is gate:
Bava Kamma - The first third, the first gate.
Bava Metzia - The middle third, the middle gate.
Bava Basra - The final third, the last gate.
If the division had been made according to subject matter, this chapter would not have been separated from the two opening chapters of Bava Basra, but this is how its place was established for us.
The Case Discussed in the Mishnah:
The case before us, and so too in the next three Mishnahs, deals with a two-story structure in which different tenants live, and in Mishnah 1 and Mishnah 3, it involves two separate owners of the two floors: one lives on the ground floor, which is called "the house", and the other lives on the floor above it, which is called "the upper story" - and this does not mean an attic, but rather an apartment on the second floor.
The question being discussed is what the law is when the entire structure has collapsed, and both owners wish to rebuild their homes. They must divide the rubble and debris among themselves - the wood and bricks that are still fit for use. The foundation of the Mishnah's ruling is that the division must be done in the fairest way possible.
The Text of the Mishnah:
"Habayis veha'aliyah shel shenayim shenafelu" - A two-story structure whose lower floor and upper floor belong to two different people, and it collapsed.
"Sheneihem cholkin" - The division is made equally and proportionately.
"Ba'etzim uva'avanim uve'afar" - The wood, the stones or bricks, and the dirt, which is the plaster material between the two floors.
An equal division assumes two things: that both sides had an identical area, which makes sense since one floor is built on top of the other, and that the height of the walls of both was equal. If the walls of one apartment were much higher than the walls of the other, it is clear that from the outset more bricks belonged to it, and one must calculate and divide the bricks in a proportional and fair manner.
From this, many deduce that the novelty of the Mishnah is this: although one might have thought that the materials at the bottom of the rubble belong to the lower tenant and the materials above them to the upper tenant, this is not the case - they take all of the ruins and divide them equally and proportionally between the two of them.
"Vero'in eilu avanim re'uyos lehishaber":
All of the above applies assuming we have no clear reason to attribute a specific item to one of the parties. However, when such a reason exists, the law is different, and therefore we evaluate which party it is more logical to assume the broken stones belong to, as opposed to the whole stones:
If the house collapsed inward: It is logical that the lower stones broke and the upper ones fell on them, and therefore the broken stones at the bottom belong to the downstairs resident, and the whole stones on top to the upstairs resident.
If the structure fell to its side: It is logical that the upper floor leaned first and its stones crashed first, and everything else fell on them afterward, and therefore we attribute the broken stones to the upper apartment.
There is logic to this reasoning, and we divide the stones accordingly. But in a situation where there is no such logical reasoning, we revert to an equal division.
"Im hayah echad meihen makir miktzas avanav" - If one of them recognizes some of his stones:
If one of the parties recognizes some of the stones as his own - for example, they have a certain stamp, frame, shape, or color - he takes those stones, "ve'olos lo min hacheshbon" - meaning they are counted as part of his share. For instance, if there are one hundred stones to divide between the two, and each is supposed to receive fifty, and one of them claims that ten stones are definitely his because they are marked with his initials - he takes those ten and receives another forty. Consequently, each receives the fifty due to him, except that he receives the specific stones he is able to identify as his own.
A claim of certainty versus a claim of doubt:
It is a fundamental rule that a person does not take something merely because he claims it is his. In a situation where one makes a "bari" claim, that the item is definitely his, and the second makes a "shema" claim, that he does not know if his fellow is right or wrong, this is not enough to allow him to take it. Therefore, this must necessarily deal with a case where the second party admits to part of the claim: he says, indeed ten bricks bear your initials and I admit that they are yours, but regarding the additional ten bricks that you claim by virtue of remembering their shape or color, I do not know.
We thus find that we have before us the law of "modeh bemiktzas" (partial admission): the upstairs resident claims twenty bricks that he recognizes, the downstairs resident admits to ten of them, and regarding the remaining ten he denies the claim or does not know. The law is that one who admits to a part of a claim must swear on the part he denied. And since the downstairs resident cannot swear that the remaining ten bricks do not belong to his fellow, since he does not know, he is obligated to swear but cannot swear - and we have a rule that anyone who is obligated to swear and cannot swear, his fellow wins his full claim.
This is therefore the situation the Mishnah is dealing with. Obviously, it is not talking about a case where both parties agree regarding a specific brick, for this is self-evident, and there is no need for a special ruling to teach us that when the two agree, they should divide according to their agreement.
In summary: At the beginning of the tenth chapter, we discussed its place in the laws of neighbors and the division of Tractate Nezikin into the three Bavas. We learned the law of the house and the upper story that collapsed: the division of the wood, stones, and dirt equally and proportionately, taking into account the area and the height of the walls; the rule of "vero'in eilu avanim re'uyos lehishtaber" - attributing the broken stones according to the manner of the fall; and the law of one who recognizes some of his stones, which are counted as part of his share, based on the laws of partial admission and one who is obligated to swear but cannot swear.