Pesak: All of Nezikin (Bava Kama, Bava Metzi'a and Bava Basra) are considered one Masechta, like we say in Bava Kama (102a) and Avodah Zarah (7a).

Implied question: Even if they are not considered one Masechta, we can ask why Bava Basra was taught after Bava Metzi'a!

We find that the Gemara asks at the beginning of Maseches Shevu'os (2a) "the Tana finished Makos. Why did he teach Shevu'os [after Makos]? Also in several places [we ask like this].

Implied question: We say in Bava Kama (102a) that regarding two Masechtos, there is no order! (Why does the Gemara in Shevu'os and elsewhere ask about the order?)

Answer: This refers to Machlokes v'Achar Kach Stam. (If Rebbi taught an argument, and afterwards taught a Stam Mishnah, this shows that he concluded like the Stam.) Rebbi did not teach to the Talmidim like the order of the Masechtos. Sometimes he taught a later Masechta before an earlier one. (Therefore, if the Stam and Machlokes are in different Masechtos, we do not know which was last.)

Answer (Ri): The reason is because he refers to the previous Perek (the last Perek of Bava Metzi'a. Its first Mishnah discusses) a house and upper story that belonged to two people, and they fell. They divide the wood..., and the Gemara calls them partners.

Also, it was taught there (in the last Mishnah) if there are two gardens, one above the other, and vegetables growing in the middle, which is a matter of partnership.

Definition: The Gemara explains that these are half-bricks.

Question (Ri): It says "v'Chafis me'Etz Ya'anenah." This implies that it is of wood!

Answer (Ri): Perhaps they used to put wood above and below.

Implied question: Why didn't it say that [the total width of a wall of] coarse rocks is six Tefachim?

Answer: [Had it said so,] we could have erred to say that each gives six Tefachim of his property.

Implied question: Why did it need to teach the measures of coarse rocks and smooth rocks? The Mishnah taught that all is according to the local custom. They do like the custom!

Answer: If the custom is to make it more than six Tefachim, they do not do so, and similarly for all [materials in our Mishnah], rather, like the Shi'ur explicit in our Mishnah.

Distinction: However, if the custom was to make it less than six, they do so. Even if the custom was [to make walls of] Lulav or laurel branches, they do, like the Gemara (4a) explains.

Question: The Gemara asked what "everything is according to the local custom" comes to include, and answered to include a place where they use Lulav or laurel branches;

We should say that it comes to include in every place, according to their custom!

Answer (R. Tam): [We follow the local custom] only regarding Lulav or laurel branches. However, less than this (to make walls thinner than the Shi'urim in our Mishnah for bricks, half bricks...), even if this is the custom, it is a commoners' custom and we do not follow it.

Inference (R. Tam): This shows that there are customs on which we do not rely, even when the Mishnah says "everything follows the local custom."

Explanation: Since [one of them] can build the wall b'Al Korcho (against the other's will, therefore, if it fell, they divide its place and the rocks);

This (that one can force the other) is either because they made a Kinyan with each other to make a wall, according to Version #1, e.g. it is still known, and we remember that they made a Kinyan.

Or, according to Version #2, it is due to Hezek Re'iyah.

Question: Why is this (if it fell, they divide its place and the rocks) due to the law that one can force the other to build?

Even without this, it belongs to both of them, even if it fell to the Reshus of one of them, since neither has a Chazis (marker)!

Source: The Gemara asks about a valley (when both wanted to build, why must each make a Chazis?] Neither should make a Chazis!

If [the rocks] belong to the one into whose Reshus they fell, what was the question? [Each] must make a Chazis, lest it fall into the other's Reshus, and he will say that [the rocks] are his!

Implied question: We say in Bava Metzi'a (100a) regarding one who swapped a [pregnant] cow for a donkey [and we are unsure whether the fetus was included, or if it was already born at the time of the swap]...

And similarly (Bava Metzi'a 116b, regarding) a house and its upper story (that different people owned them, and they fell)...

[In both places] we ask "let us see in whose Reshus they are (the calf, or the intact wood and rocks)", and the other is ha'Motzi mi'Chavero Alav ha'Re'ayah (he must bring a proof in order to receive)!

Answer: That is because there, the matter was clear at the beginning, and the Safek arose in the Reshus of one of them, but here the Safek arose at the beginning;

If they would come to divide while the wall is intact, they would split it evenly, due to Safek;

This is even according to Rabanan who argue with Sumchus, and do not say that we divide property when there is a Safek who owns it (rather, they leave it in its Chazakah, and the other is ha'Motzi mi'Chavero Alav ha'Re'ayah);

Here they agree, since neither has a greater Chazakah than the other.

Therefore, even when it fell into the Reshus of one of them, the other does not lose his rights.

Implied question: Why don't we say here Kol d'Alim Gavar, like (below, 34b) when each of two people claims that he inherited [a field, or a boat] from his ancestors?

Note: Some explain that Kol d'Alim Gavar means that whoever can bring better supporting evidence that it is his, he gets it. Others say that Beis Din does not rule about it. Whoever physically overpowers the other, he keeps it.

Answer: There, there is no Drara of money. Here, there is Drara of money.

Note: In Bava Metzi'a (2b), Tosfos explained that Drara of money is when even without their claims, Beis Din has a Safek. Avi Ezri (1) explains that due to the Safek, it is as if both are holding and Muchzak in it.

Answer (Ri): This is the Gemara's question below "this is obvious!", like Rashi explained;

Even if the law of our Mishnah was not clear to us, that at the beginning they forced each other, they would divide equally, even if it fell to the Reshus of one of them, like is clear from the case of a valley (we asked why both must make a Chazis).

The Gemara answers that the Chidush [of our Mishnah] is when it fell to the Reshus of one of them, i.e. and [the rocks] stayed in his Reshus a long time;

One might have thought that since they stayed in his Reshus a long time, we should believe him that he made the entire wall himself;

He would be believed through a Migo. If he wanted, he could have said "I bought [your rocks] from you", and he would be believed, because they delayed a long time.

Implied question: It says in Bava Metzi'a (116b) that partners are not exacting with each other [about leaving jointly owned property in the Reshus of one of them. If so, the delay does not prove that they are his!]

Answer: The case is, they delayed longer than what is normal. Because they are partners, will we say that they are never adamant?!

Implied question: Why is this unlike Godros (animals and slaves, which can walk by themselves), which have no Chazakah?

Answer: That is because we do not know who had them. (Perhaps they came here by themselves.) Here, [if some rocks belonged to the neighbor], he should not have delayed them so long in [the other's] Reshus.

Continuation of answer: The Mishnah teaches that this is not so. Since initially it was incumbent on both of them to make [a wall], he is not believed to say that he made it himself, for this is a Migo against witnesses;

Anan Sahadei (it is so certain that we can testify) that he did not make the wall himself, since the law is that he could have forced his friend (neighbor) to make it with him.

Distinction: However, in a valley, if they delayed a long time, he would be believed to say that he made it, through a Migo, that if he wanted, he could have said "I bought [your rocks]."

Limitation: This answer is only regarding the rocks. Obviously, they divide the place of the wall;

Since the Mishnah taught [that since he could have forced his friend, they divide] the rocks, it mentioned also the place [even though obviously they divide the place even in a case that one cannot force his friend.

Implied question: Why does it say "they thought that"? We conclude like this!

Answer #1: It says "they thought that" because this version is not primary, due to the question below (2b. If Mechitzah means wall, the Mishnah should have said 'they build it'!)

The answer given (had it said so, one might have thought they build a mere Mesifas, i.e. a wall with windows) is a mere Dichuy. The Halachah follows Version #2. Also R. Tam rules like this;

For parallel structure with what it says here "they thought that", it says so also in Version #2 (even though the Halachah follows it).

Answer #2 (Ri): In Nedarim (11a) we find that it says "they thought that", even though the Halachah follows it).

Alternate text: Some texts say "d'Tanan" (a Mishnah teaches).

Rejection (R. Tam): There is no such Mishnah anywhere. (It is a Beraisa.)

Question: If so, how did we resolve from here that R. Meir obligates for Dina d'Garmi? (Most say that these are ways of causing damage that are more direct, and more certain to result in damage, than Gerama. One opinion equates Garmi and Gerama.)

If this were a Mishnah, this would be fine, for a Stam Mishnah is [assumed to be] R. Meir.

Answer (R. Tam): The Gemara derives that it is like R. Meir due to the Mishnah in Kil'ayim brought there. If [Reuven] draped his vine over Shimon's grain, it forbids [both of them], and [Reuven] is liable to pay for it;

That is a Stam Mishnah. Therefore, also this Beraisa [of one who did not fix the wall] is R. Meir. It is not proper to elaborate more here.

Explanation: [The owner of the grain] tells the owner of the vineyard [to fence the breach] for he is the damager, for the four Amos that Chachamim said to distance are for the sake of working the vineyard, like we say below (26a).

Suggestion: According to R. Yosi, who says below (18b) that the victim of damage must distance himself [the owner of the vineyard need not fence it. If his neighbor wants to save his grain, he must fence it himself!]

Rejection: Rav Ashi taught below (25b) that R. Yosi agrees in a case of arrows (damage that comes directly from the person's hand, that the damager must distance himself).

Implied question (Ri): Why does it say "he tells him to fence", and not "he must fence"?

Answer (Ri): He must warn him. If he did not warn him to fence, he need not pay for the loss [of the grain].

Implied question: Why does it say twice "if it was breached, he tells him to fence"?

Answer #1: Also the second time when it was breached, he must warn him, for he does not think that he is obligated to fence every time [it is breached].

Question: The Ri was unsure about the third time, whether he must warn him every time. Or, perhaps it suffices to warn him twice, and he need not warn him more.

Answer #2 (R. Tam): The reason it says twice is to teach that if it grew one part in 200 combined between what it increased in the first breach [until he fixed it] and in the second breach, they do not join to forbid;

This is because each amount [of forbidden growth] is Batel [before the next forbidden growth comes]. I elaborated in Bava Kama (100b) and Shabbos (65b).

Explanation: This is only if he despaired. If he did not despair, and he is constantly engaged in fencing, even if it grew [one part in] 200 [of the size before he fenced it], it is permitted;

Source - Citation (Kil'ayim 5:6 - Mishnah): If one saw Yerek growing in his vineyard, [and was heading towards it] and said "when I get there, I will uproot it", [even] if it grew [one part in] 200, it is permitted. [If he was heading away from it, and said] "when I return, I will uproot it", if it grew [one part in] 200, it is forbidden.

Inference: When he is pursuing to uproot it, even if it grew [one part in] 200, it is permitted.

Explanation: This is because it says "Lo Sizra Karmecha Kil'ayim" - this resembles seeding, which he wants.

Implied question: Hezek she'Eino Nikar is not called damage (Gitin 53a)!

Answer (Ri): This is considered Hezek Nikar, for it is evident that it is Kil'ayim when he sees the vines in the field [with no wall between them and the grain].

Implied question: Being Metamei [another's Taharos should be considered Hezek Nikar] when he sees [a dead Sheretz] on the Taharos!

Answer: It is not considered Hezek Nikar, for one [who sees this] does not know whether the Taharos were Huchshar. (If they were not, they remain Tahor. Even if water drips from them, perhaps the owner did not want the water. Ohel Moshe asks how Tosfos can answer for one who is Metamei liquids, which do not need Hechsher!)

Suggestion: Perhaps [Kil'ayim] is Hezek she'Eino Nikar, and Chachamim fined him, like they fined one who is Metamei, lest everyone be Metamei Peros of his colleague!

Rejection #1: Here there is no concern for this, for the owner of the vineyard also loses (his grapes become forbidden).

Rejection #2: If it were a fine, he should be liable only if he was Mezid.

Note: What is Tosfos' source that he is liable even if he was not Mezid? We discuss one who was warned! R. Akiva Eiger (Kil'ayim 7:5) asked that R. Meir decrees Shogeg due to Mezid. The Rashash answers that here, "Mezid" means doing an overt act.

Explanation (Ri): Because there are several difficulties if it means wall, like we ask below, therefore the Gemara strains to explain that Mechitzah is a division, even though everywhere, Mechitzah is a wall.

Explanation: Below, we establish this when there is no Din Chalukah.

Question (Ri): Why did the Tana discuss when there is no Din Chalukah, and he taught a case when they wanted? He should not teach that they wanted, and discuss a Chatzer with Din Chalukah! (It is not common to split a Chatzer without Din Chalukah, for each partner does not receive a useful share.)

Answer (Ri): One might have thought that when there is no Din Chalukah, he can say "I agreed to you to divide on condition not to make a wall. I did not agree on condition to make a wall."

Support: In some Seforim, it asks and answers like this explicitly at the end of our Sugya. (In our Gemaros, it is in brackets on 3a.)

Opinion #1: The Mishnah teaches "they wanted" regarding [building] a Mesifas, even though without wanting, they make a Mesifas against their will;

This is clear from the Gemara below. It says "[don't they divide with] a wall? No, with a Mesifas." This refers to an inferior Mesifas;

However, when they want, they make a Mesifas of Gevil and Gazis, like the local custom;

Explanation #1: It is called Mesifas because it is full of windows, like the Aruch explained, and it does not protect from Hezek Re'iyah.

Explanation #2: [It is called Mesifas because] it is not 10 [Tefachim] tall, like is proven below regarding a roof adjacent to a Chatzer;

Rav Nachman said that he makes a wall 10 tall. The Gemara asked "for what is it? If it is for Hezek Re'iyah, we require four Amos!" If it is so [his neighbor will fear to cross it, lest] he be caught [trespassing] like a thief, a Mesifas suffices!

Opinion #2 (Rashi): The Mishnah says "they wanted" regarding the division.

Objection #1: We conclude that "Mechitzah" is a wall. If it meant division, the Mishnah should have taught "[they wanted] to divide"!

Objection #2: How can we say that the Hava Amina was for a mere Mesifas? We learn this from the Seifa!

The Seifa teaches "but when both of them want, even less than this (each partner will receive less than four Amos), they divide. At least, they make a Mesifas.

Objection #3: How could we say with a mere Mesifas? The Mishnah explicitly teaches [the Shi'urim for] uneven rocks, smooth rocks...!

Explanation: We challenge the one who says [that it is a] wall, like all the questions below;

When they were Makneh to make a wall, each one was Makneh like the other. Obviously, they build it in the middle!

However, according to the opinion that it is a division, it needs to teach this;

One might have thought that due to Hezek Re'iyah, he must help build the wall, but he need not build [even part of] it in his property due to this.

Explanation: Below, we conclude that it means that similarly, a garden is like a place in which the custom is to fence. Therefore, he properly infers that Hezek Re'iyah is called damage.

Question: From this reason, he should be obligated to fence also in a valley!

Answer: A garden is different, for there they grow vegetables for eating. It always has fully grown crops;

However, a valley's crop (grain) is fully grown only one month in a year. He is not obligated to fence. However, one may not stand [and look] when the crop is fully grown.

Question: According to the opinion [that Mechitzah means] division, since we learn [from the Reisha] that even in a Chatzer [Hezek Re'iyah] is called damage, all the more so in a garden! Why did [the Seifa] need to teach further "and similarly in a garden"?

Answer: It needed to teach "and similarly in a garden" for the sake of uneven rocks and smooth rocks [to teach that the same width of wall is needed as in a Chatzer].

Explanation: Because they became used to doing in the Chatzer matters that require privacy, and they did not learn to be careful from each other, [therefore they must rebuild the wall].

Explanation: Obviously, it is different when it fell. Just the contrary, he should prove from the fact that it taught when it fell, that normally (if there was no wall until now, Hezek Re'iyah) is not considered damage!

Implied question: Below, it connotes that we discuss a Chatzer that is not adjacent to Reshus ha'Rabim!

Answer: In any case, there is Hezek [Re'iyah] of the Rabim, for sometimes people in Reshus ha'Rabim are crowded, and enter there (near the Chatzer's opening), like we say below.

Implied question: R. Shimon ben Gamliel argues with this reason that sometimes Reshus ha'Rabim is crowded! (Why does he obligate a door?)

Answer: In any case, from afar they could see inside [the Chatzer, if there were no door].

Support: This is why he argues only about a Beis Sha'ar, but he agrees that we force him to build a door.

Question: Even if they divide with a Kosel, perhaps it means that they do not divide the Chatzer, even if one of them wants to build the wall in his property, until there is enough [area in the joint Chatzer, so that after they divide] there will be four Amos for each partner;

We infer that if there will be four Amos for each, they divide, if one of them wants to recess and build [the wall] in his property!

Answer: "They divide" connotes in the middle. If it taught like I said, it should have taught "we do not make a wall in a Chatzer unless there will be..."

Question: Why don't we bring from the Beraisa below (6b)?

Citation (6b) Beraisa: If there are two adjacent Chatzeros, and one is above the other, the owner of the top Chatzer may not say "I will build [a low wall on my property]." Rather, he helps build from below [and four Amos above the ground of his Chatzer]. This shows that Hezek Re'iyah is considered Nezek!