Opinion: It appears that the Gemara's question is regarding a case where he says "even Reuven." (Note: Don't think that it asked this question regarding Shimon to exclude a case of "even Reuven" where the law is clear.)

Question: The marriage (i.e. Kidushin) should not be valid, as she is forbidden to him because she is a married woman! (Note: Accordingly, how could our Gemara think that this means her original Get is invalid?) How is this different from the following Tosefta? The Tosefta states, "On condition that you should not marry my father or your father," is a valid Get. "On condition that you will not have relations with my father or your father," is not a valid Get, as we suspect that she may have relations with them. This implies that even if she would marry her father or his father after the Get was "on condition that you should not marry my father or your father," the Get was still valid (and is not invalid retroactively). (Note: This is because the marriage to his or her father is a halachic impossibilty. Being that he forbade it, she is considered towards him to be a married woman. This is as opposed to having promiscuous relations which is always possible.) Why, then, is the Get in our Gemara ruled invalid?

Answer#1: The case here is where she got up (according to Maharam Shif the text is "v'Avrah" -- "and she transgressed") and married (the person she was not supposed to marry) after the husband who divorced her (with this condition) died. (Note: Accordingly, she cannot be considered a married woman, as the person who she would be otherwise married to is dead.)

One must similarly say later regarding the case where he says, "you should not have relations with my father or your father" we do not suspect that she will have relations with them because she is forbidden from doing so. This implies that if the condition would be about someone else we would suspect that she might have relations with him, even though she is forbidden to be with him because to him she is a married woman (due to this condition). Even so, we suspect that she might be with him after the death of the husband who divorced her (with this condition).

The Tosefta can be answered so that it does not argue on our Gemara. When it says in the Tosefta, "on condition that you do not have relations with my father or your father," is not a valid Get as we suspect that she might have relations with them, it means that if it seems plausible that she may have relations with them the Get is invalid. It is coming to tell us, "on condition that she should not marry etc." is even a Get if she marries them.

Answer#2: Alternatively, the Tosefta is teaching us that in a case, "on condition that you will not have relations with my father or your father," it does not mean that she should not marry, but rather it is forbidding promiscuous relations.

Explanation: The reason is that being that she married someone who she was permitted to marry, all of her marital status was given to him, and the first person's marriage to her totally went away.

Question: If so, Rebbi Yosi who says that he thinks that the words of Rebbi Elazar ben Azaryah are the most correct of all of them, and he holds of these questions,, must also hold of Rebbi Yanai's statement in the name of an elder. If so, this should serve as a question on Rebbi Yochanan who argues on Rebbi Yanai (as this means Rebbi Yochanan is arguing with Rebbi Yosi)!

Answer: It is possible to say that when Rebbi Yosi says that he thinks Rebbi Elazar's words are correct, it is not because of these questions. (Note: He therefore does not necessarily hold like Rebbi Yanai.)

Question: Being that Rebbi Elazar derives his opinion from a Pasuk, how do these elders refute what he says? It seems to be a Torah instruction!

Answer: Being that they can reply to his position, they understand that it is logical that the Pasuk he quotes should be understood as it is understood by the Rabbanan.

Implied Question: Rabbi Yehoshua compares them even though they are obviously not completely comparable. Before her first marriage she was permitted to everyone, and after her first marriage she is forbidden to the relatives of her first husband. (Note: How, then, can Rebbi Yehoshua make this comparison in status?)

Answer: Even so, he compares them in the following manner. Just like she was originally unmarried, so too before her second marriage she must be completely detached from her first husband as far as marital status is concerned. She cannot have any marital connection to him at all.

Question: This is difficult. Who does Rebbi Eliezer admit to? According to the Rabbanan who argue on him it is not a Get, and she is not permitted to anyone. (Note: Rebbi Eliezer holds it is a Get. To whom is he admitting?)

Implied Question: Rebbi Yosi ha'Glili, who is included in the Rabbanan's opinion here, derives "Kares" from "Kerisus" in the Gemara earlier (21b). However, in our Gemara the Rabbanan (and Rebbi Yosi ha'Glili) do not derive "Kares" from "Kerisus." (Note: How do we resolve this apparent contradiction in the position of Rebbi Yosi ha'Glili?)

Answer: Our Gemara merely means that the Rabbanan (and Rebbi Yosi) do not derive "Kares" from "Kerisus" in this fashion. Rebbi Yosi does derive from it in the way stated earlier (21b).

Question: Rabeinu Yitzchak has difficulty with this. In Yoma (13a), regarding the position of Rebbi Yehudah that they used to prepare another wife for the Kohen Gadol, the Gemara quotes Rava's position in a different fashion.

The Gemara there states that the Kohen Gadol gives his wife a Get, "on condition that one of you (including his other new wife) will die." The Gemara asks, would this indeed be a Get? Doesn't Rava say that if someone says, "This is your Get on condition that you do not drink wine for the rest of my and your life," this Get is invalid? However, if he makes it contingent on, "all the life of Ploni" it is a Get.

This is unlike our Gemara's conclusion, and unlike our Gemara's original thought, that he must not have said, "all the days of my life." (Note: Why does the Gemara in Yoma (ibid.) quote Rava as saying that such a case is indeed invalid?)

Answer: Perhaps the Gemara there does not worry about this, and quotes, "all the days of my life" anyway as it is originally quoted along with "and your life" that is not a valid Get, as we conclude as well (that regarding her life it is not a Get).

Question: The Ri has difficulty with this. Why isn't the Get valid in Yoma when he says, "on condition that one of you will die?" Why should this be different from making this dependent on someone else's life which is valid? For each woman who this is dependent on, it will not affect her personal Get if she dies. (Note: In other words, while technically this depends on the woman in the Get, the condition towards each woman is essentially, "that your friend dies." Her personal Get is not affected by her own death.)

Implied Question: Our Gemara's second possibility is not, "or perhaps it does not make a difference" as it is regarding Rebbi Eliezer's position. (Note: Why not?)

Answer: Right when (i.e. immediately before) Rava said, "being that he cut off their marital relationship he did so for good," he realized that this was correct (and therefore said this instead of, "perhaps it does not make a difference").