(Mishnah): At first, [one who wanted to invalidate a Get] would assemble a Beis Din elsewhere, and be Mevatel it. R. Gamliel enacted that people not do so, for Tikun ha'Olam (for the betterment of the world).

At first, he would change his name, her name, the name of his city and the name of her city. (This will be discussed.)

For Tikun ha'Olam, R. Gamliel the elder enacted that they should write Ploni and every name that he has; Plonis and every name that she has.

(Gemara) Question: Does this not argue with Reish Lakish? Reish Lakish said that one cannot be Mevatel his Shelichus verbally!

Answer: In Beis Din [is different], for it has great power.

Mishnah): For Tikun ha'Olam.

Opinion #1 (in the name of Reish Lakish): This is lest she come to Mamzerus (these opinions will be explained);

Opinion #2 (in the name of Reish Lakish): This is lest she be an Agunah (unable to remarry, like we will explain).

The one who says lest she be an Agunah, this is lest she think that he was Mevatel, and [really] he was not Mevatel. It turns out that she is an Agunah;

The one who says lest she come to Mamzerus, she thinks that he was not Mevatel, and [really] he was Mevatel. She remarries without a [Kosher] Get, and it turns out that her children are Mamzerim.

(R. Mana): I went in a caravan, and I heard R. Yakov bar Acha and R. Imi say in the name of Reish Lakish, it is lest she come to Mamzerus.

(Rav Huna): Even the one who says lest she be Agunah, he holds that [also there is concern] lest she come to Mamzerus!

She thinks that he was Mevatel, and [really] he was not Mevatel. If another (Ploni) comes and is Mekadesh her, Kidushin takes effect in her, and she thinks that it did not take effect in her;

She waits until her first husband dies, and she goes and remarries (but really, she is Ploni's wife). It turns out that her children come to Mamzerus. We explained this like NO'AM YERUSHALMI.)

Note: Why does she think that he was Mevatel? The RASHBA (33a) says that she heard a Kol (talk) that he was Mevatel. If she is so sure that it is true, that she ignores the Kidushin, why did she accept Kidushin?! Perhaps the case is, she received the Get e.g. six months after the date. She accepted Kidushin, and within a month of getting the Get, she heard (perhaps from witnesses) about the Bitul. She reasons that if Shali'ach ha'Get needed six months to get here, surely those who knew about the Bitul could not get here in less than a month! She deduces that Bitul was before she received the Get. She errs; perhaps there was a long delay until her husband found a Shali'ach, or the Shali'ach went elsewhere first, or tarried on the way... (PF)

Question: If he transgressed and was Mevatel it (not in front of her or the Shali'ach, what is the law?)

Answer: We learn from the following [Beraisa]. If he was Mevatel it (not in front of her or the Shali'ach), it is Batel. Rebbi says so;

R. Shimon ben Gamliel says, he cannot nullify it, nor add stipulations.

Question: R. Shimon ben Gamliel said properly - [if not,] what power does Beis Din have?! What is Rebbi's reason?

Answer: Mid'Oraisa, he is Mevatel. Did [Chachamim] say that he was not Mevatel?! Do their words uproot Torah law?!

Question: [One who tithed] olives on (i.e. to exempt Tevel olive) oil, or grapes on wine - is it Torah law that one may tithe [so], and they said that he cannot tithe so, due to stealing from Kohanim (lest one give according to the volume of the oil or wine, and according to the volume of olives or grapes needed to make it)...

And further, they said that if he transgressed and tithed [so], his Terumah is not Terumah! (We find that Chachamim uprooted Torah law!)

. Oshaya bar Aba (to R. Yudan Nesiya): Who can explain to us the Halachah of your grandfather (Rebbi)?! (ALEI TAMAR - sometimes Halachah is called 'Agadah.')