(Mishnah - Mikva'os 2:2): [For any light Tum'ah, for any Safek whether or not he or it immersed,] the Safek is Tahor. R. Yosi is Metamei.

(R. Yonah): R. Yosi is Metamei only when there is evidence [that the Tevilah was invalid, i.e. the last case mentioned in the Mishnah, when the Mikveh was measured now and found to be deficient].

(R. Yosi (an Amora)): Even elsewhere [where there is no evidence], R. Yosi is Metamei.

Contradiction: R. Yosah contradicts himself! In our Mishnah, R. Yosi said that Avtulus testified in the name of five Chachamim that a Safek Eruv is valid, and here you say so (R. Yosi is Metamei in a case of Safek Tevilah)!

Answer #1: There, he himself [is Metamei]. Here [he is Machshir a Safek Eruv] in the name of five Chachamim. (The Seifa explains that this that R. Yosi is Machshir, he said in the name of five Chachamim. However, he himself disqualifies.)

Assumption: We wanted to say that the [first Tana] who says there Tahor, here he permits [a Safek Eruv]. The one (R. Yosi) who says there Tamei, here he forbids.

Note: There is an implied question, for presumably, the Stam first Tana there is R. Meir. Further, a Tosefta explicitly says that R. Meir is Metaher, and here he disqualifies a Safek Eruv!

Rejection: Even the one who says there Tamei, here he agrees that it is permitted [for Eruv has no source from the Torah, unlike Tum'ah].

Note: This is a second (and better) answer to the contradiction in R. Yosi. However, it strengthens the implied question, i.e. the contradiction in R. Meir. (We explained this like PNEI MEIR.)

Answer (R. Chinena): There, they argue only about [Tum'ah] mid'Rabanan. We are lenient about a Safek mid'Rabanan. Eruv [Techumim] is mid'Oraisa. We are stringent about a Safek Torah.

Question: [What is the source] that Eruv [Techumim] is mid'Oraisa?

Answer (R. Yonason, in front of R. Chiyah Rubah, citing R. Shimon bei R. Yosi ben Lekunya): One is lashed for Techumei Shabbos mid'Oraisa;

Question (R. Chiyah Rubah): Regarding Shabbos there is only Skilah and Kares (there is no Isur of lashes)!

Answer (R. Yonason): It says "Shevu Ish Tachtav Al Yotzei Ish mi'Mekomo ba'Yom ha'Shevi'I''!

Rebuttal (R. Chiyah Rubah): [There are no lashes for this, for] it does not say "Lo'', rather, "Al''!

Answer (R. Yonason): (There are lashes even when it says "Al''!) It is written "Al Tochlu Mimenu Na'' not [and there are lashes for this, even though] it does not say "Lo'', rather, "Al''!

Note: Seemingly, R. Chiyah should argue also about this, and say that there are no lashes for this, since it says "Al'', and not "Lo''! It is not listed among the Aveiros of lashes in Perek 3 of Makos. We do find that Mechilta of R. Shimon bar Yochai (12:9) says that there are lashes for this. Perhaps R. Chiyah would not want to argue with R. Shimon, who was from the previous generation; we do not find anyone who argued with R. Shimon.

(R. Yosi bei R. Bun): [Even though R. Yonason properly answered R. Chiya,] he retained his opinion and he retained his opinion (neither retracted).

(R. Shmuel bar Sisarta): They made [Safek] Eruv like a Safek of a deaf-mute (i.e. one who has no Da'as. We are lenient about a Safek Tum'ah when Ein Bo Da'as Lish'ol (no one with Da'as was present).

Question (R. Yirmeyah): This is if the Eruv is intact [but it left the Techum or became Tamei. Why are R. Yosi and R. Shimon Machshir] even if it was burned?! (If Techum is mid'Oraisa, how can we be lenient? It is not here, so we cannot say that we leave it in its Chazakah!)

Answer (R. Yosah): I answer like R. Hoshayah said - when you investigate, at the end you find that Techumim of Shabbos are not mid'Oraisa.

Question (R. Mana): Granted, the Techum of 2000 Amos is not mid'Oraisa. Is the Techum of 4000 Amos mid'Oraisa?

Answer (R. Shimon bar Karsenah citing R. Acha): The only Techum that is mid'Oraisa is 12 Mil, like Machaneh Yisrael.

(Mishnah): One may stipulate about his Eruv and say 'if Nochrim come from the east, my Eruv is in the west (I will flee to there). If they come from the west, my Eruv is in the east. If they come from both directions, I will go where I want. (Retroactively, my Eruv was in that direction.) If no they do not come, I am like people of my city (without an Eruv).'

(Gemara): Our Mishnah teaches that [one may stipulate] about his Eruvin (plural).

(R. Lazar): Who is the Tana who taught 'if [Nochrim] come... if they do not come'? It is R. Meir.

Question: Which teaching of R. Meir [does he refer to]?

Answer #1 [Talmidim]: It is what R. Meir taught about Kidushin;

(Beraisa): If one said to a woman "you are Mekudeshes to me on condition that rain falls'' - if rain fell, she is Mekudeshes. If not, she is not Mekudeshes;

R. Meir says, whether it falls or does not fall, she is Mekudeshes, unless he doubles his Tenai (adds "you are not Mekudeshes to me if rain does not fall.'' Therefore, here he needs to discuss if they come, and if they do not come.)

All agree that if he said to a woman "you are Mekudeshes to me after rain falls'' - if rain fell, she is Mekudeshes. If not, she is not Mekudeshes.

Answer #2 (R. Yosah): It is R. Meir of Eruvin. (Even if he holds that Kidushin does not need a Tenai Kaful, e.g. if he said 'from now' or 'after', here he needs it, lest we say that if they do not come, he is in Chamar Gamal because uprooted the Techum of his city.)

(Mishnah): If it is a Safek [whether an Eruv became invalid], R. Meir and R. Yehudah say, he is in Chamar Gamal. R. Yosi and R. Shimon say, a Safek Eruv is valid.

(R. Yosah): R. Meir said [that Tenai Kaful is needed] only to be stringent. (Do not say that if he did not double the Tenai, in any case his Eruv is valid. Rather, it is a Safek, and he would be in Chamar Gamal.)

Support (R. Mana): He does not [have the Techum of] his Eruv, for his Eruv did not acquire for him. Also, he is not like people of his city, since he already intended to uproot himself from the Techum of his city;

Here (you are Mekudeshes to me if rain will fall, without Tenai Kaful, he is likewise stringent. Before rain falls), she is not [totally] Mekudeshes to the first [who was Mekadesh her], and [if someone else was Mekadesh her] she is not [totally] Mekudeshes to the second because the first did not double the Tenai [so the first Kidushin is not totally Batel. We explained this like YERUSHALMI KI'PESHUTO.]