Our Mishnah invalidates a 'Chazakah she'Ein imah Ta'anah' - a Chazakah that is not based on a legal claim, but on the fact that nobody told the Machzik to leave.

This ruling is not confined to a three-year Chazakah, but applies equally to a Chazakah that takes effect immediately (such as that of the right of placing one's beams on his neighbors wall, if his neighbor is silent even just once).

A plausible Ta'anah - negates the owner's right to claim that the Machzik entered his R'shus without permission (because if that were so, he ought not to have remained silent).

've'ha'Ba mishum Yerushah, Eino Tzarich Ta'anah' - does not mean that he is completely believed when he claims that the land previously belonged to his father; in fact, he is obligated to prove that his father lived there for at least one day.

The Tana find it necessary to rule that a Chazakah without a Ta'anah is not a Chazakah - because we might otherwise have thought that in reality, he purchased the field for which he received a Sh'tar, only (not aware of the Din of Chazakah) he was afraid to say so, because then Beis-Din would insist that he produces his Sh'tar (which he has lost).

If the Machzik claims that this is what he meant - he is believed.

When a flood swept away the wall that divided between Rav Anan's field and his neighbor's - he built a new wall, but inadvertently moved it forward into his neighbor's field.

When Rav Nachman obligated him to move his wall back to its original location - he maintained that he had a Chazakah (immediately).

Rav Nachman rejected this reply however, even though it was based on the opinions of Rebbi Yehudah and Rebbi Yishmael in the previous Mishnahs - because the Halachah is not like them.

And when Rav Anan claimed that his neighbor had been Mochel, Rav Nachman finally explained that - his neighbor's Mechilah, which was based on the same error that led him to initially believe that he had built the wall in his own R'shus, was meaningless (since it was a Mechilah be'Ta'us [made in error]).

When a torrent swept away Rav Kahana's dividing wall, he too, rebuilt it inside his neighbor's field, though unlike the previous case Rav Kahana denied having done so.

When one witness testified that he had indeed encroached two rows of his neighbor's field, and a second witness said it was three, Rav Yehudah ruled that since both witnesses agreed on two rows, Rav Kahana was obligated to move his wall two rows back.

Rav Kahana queried this ruling on the grounds that it conformed with Rebbi Shimon ben Elazar's interpretation of the Machlokes between Beis Shamai and Beis Hillel, who, in a case where ...

... one pair of witnesses testify that Reuven owes Shimon one Manah, whereas a second pair say that he owes him two - agree that Reuven must pay Shimon one Manah ('she'Yesh bi'Chelal Masayim Manah').

... one witness testifies that Reuven owes Shimon one Manah, whereas a second witness says that he owes him two - argue whether he is Chayav to pay or not. Beis Hillel take the same stance as they do in the case of two pairs of witnesses; whereas in the opinion of Beis Shamai, this is considered a discrepancy, in which case both testimonies are canceled and the money remains where it is. (Incidentally, Beis Hillel's reason for not considering this a discrepancy is because we assume one of the witnesses to have been careless in picking up the details, but was not deliberately lying [see Tosfos DH 'Asa']).

The basis of Rav Kahana's objection was that - this was the opinion of Rebbi Shimon ben Elazar, and he had a letter from Eretz Yisrael to prove that the Halachah was not like him (but that Beis Hillel agreed with Beis Shamai in the case of two single witnesses [like Beis Shamai agree with Beis Hillel in the case of two pairs]).

Rav Yehudah replied that - he would acknowledge the letter when he saw it.

(It seems that Rav Kahana never did bring that letter and) the Halachah is - like Rav Yehudah.

When Shimon asked Reuven what he was doing in his attic in Kashta, he substantiated his Chazakah - by claiming that he had purchased it from Levi who had bought it from him (Shimon).

Rebbi Chiya - obligated him to prove that Levi had lived in the attic for one day.

The principle that absolved Reuven from having to prove that the seller had purchased the land was - 'To'anin le'Yoresh ve'To'anin le'Loke'ach' (Beis-Din will present any argument that an heir or a purchaser is unable to, because through no fault of theirs, they are not conversant with the facts), as we learned in 'Lo Yachpor'.

Rav objected to Rebbi Chiya's ruling on the grounds that he ought to have been absolved even from proving that the seller had lived there for one day - due to the possibility that Levi sold it to Reuven on the same night that he bought it, because he offered him a higher price.

Rav referred to Rebbi Chiya as 'Chavivi' - because 'Chavivi' means 'my uncle', which is what Rebbi Chiya was to Rav (from both his father's and his mother's sides).

Rebbi Chiya would have believed Reuven even if he had claimed that Levi had purchased the land from Shimon in his presence - because he had a 'Migu' in that he could have claimed that he purchased it directly from Shimon.

Had he claimed that Levi told him that he had purchased it from Shimon however - he would not have believed him.

Rava proves Rebbi Chiya right from our Mishnah 'ha'Ba mishum Yerushah Eino Tzarich Ta'anah' - which implies that he does not require a Ta'anah, but that he does require some sort of proof.

We refute Rava's proof however, on the grounds that - what the Tana may mean that a Yoresh does not require any Ta'anah at all, and that the three-year Chazakah will suffice on its own.

Even assuming Rava's inference to be correct, this does not necessarily reflect the ruling by a purchaser, who might not require any Ta'anah at all - because (unlike a Yoresh), the fact that he paid money for the field proves that he must have known that the seller purchased it (since one does not tend to throw one's money down the drain).

We ask what the Din will be if Levi (the seller) was seen in Shimon's field measuring and making inquiries about purchasing it. The She'eilah is - whether that is sufficient proof to establish the property in Reuven (the purchaser)'s domain or not.

According to Abaye, it is. Rava disagrees - because many people inquire about property, and then decline to purchase it.

We discuss a case where Shimon, Levi and Yehudah (one year each) make a combined Chazakah on Reuven's field. The problem is - that Reuven can justify not making a Mecha'ah, because, he claims that their Chazakah was not conventional, and that in fact, they were afraid to make a conventional Chazakah because they knew that Shimon had not purchased the field from Reuven.

Nevertheless, we rule that, despite Reuven's claim, the Chazakah is indeed valid, though Rav restricts it - to a case where Levi and Yehudah (not Shimon, who claims to have lost his) each purchased the field with a Sh'tar ...

... because then, there is a Kol (a rumor) substantiating the sale of the field (which Reuven should have noted), but not by an oral sale, where there is no Kol, and where Reuven can therefore claim that he did not know about the purchases.

Rav rules that if someone sells his property with witnesses (accepting responsibility [but without a Sh'tar]) - he may nevertheless claim from Nechasim Meshubadim (suggesting that there is a Kol with witnesses alone).

To reconcile Rav's two rulings we conclude that - without a Sh'tar, there is no automatic Kol, which explains why in the current case, the owner, who sees an unconventional Chazakah, does not find it necessary to make a Mecha'ah. On the other hand, a few discreet inquiries will easily reveal that the fields were sold, in which case, with regard to Rav's second ruling, it is the (second) purchaser's own fault for taking the risk of buying sold property without making those inquiries.