Summation of question: But what is the source that R. Akiva does not hold like R. Yosi?

Answer #1 (Rav Kahana): If he held like R. Yosi, surely there would be a Mishnah or Beraisa [teaching his opinion] that is Posel a Revi'i of Terumah and a Chamishi of Kodesh;

Objection: May we rely on this [to say that he disagrees with R. Yosi]?!

Answer #2 (Rav Ashi or Rav Kahana): We have an explicit proof of this!

(Mishnah #1): A Keli joins Kodesh inside it [if there are pieces of Kodesh inside, even if they do not touch each other, if Tum'ah touches one of them it is as if it touched all of them], but it does not join Terumah;

A Revi'i of Kodesh is Pasul; a Shelishi of Terumah is Pasul.

(R. Chiya bar Aba): Mishnah #1 is derived from R. Akiva's testimony:

(Mishnah #2): R. Akiva further testified that if a Tevul Yom touched part of the Soles (fine flour of a Minchah), Ketores (incense), Levonah (frankincense) or coals, he was Posel all of it.

Summation of answer: It says that a Revi'i of Kodesh is Pasul, but not a Chamishi; a Shelishi of Terumah is Pasul, but not a Revi'i.

Inference: He holds that Tziruf (joining) is only mid'Rabanan (Rashi - since he learns from Levonah and coals, which are not foods, they Mekabel Tum'ah only mid'Rabanan; Tosfos - these are mid'Oraisa - rather, R. Akiva adds to the law taught previously of Tziruf of ashes of Parah Adumah - its Tum'ah is mid'Rabanan).

He argues with R. Chanin:

(R. Chanin): Tziruf is mid'Oraisa - "Kaf Achas" - teaches that everything in the bowl [of Ketores] is considered like one.

(Mishnah): [R. Chanina Segan ha'Kohanim testified that] if a needle was found in [Kodesh] meat that the knife and hands are Tehorim, but the meat is Tamei (this will be explained);

If it was found in the Peresh (internal excrement), everything is Tahor.

R. Akiva: This shows that Tum'ah of the hands (see note 14 in Appendix) does not apply in the Mikdash!

Question: He should learn that Tum'ah of hands and of Kelim (i.e. mid'Rabanan Tum'ah of Kelim, e.g. that liquids Metamei Kelim) do not apply in the Mikdash!

Answer #1 (Rav Yehudah): Tum'ah of hands was decreed before Tum'ah of Kelim (perhaps the testimony preceded the decree of Kelim).

Objection (Rava): Both of them were decreed on the day of the 18 decrees!

(Mishnah): The following Posel Terumah [mid'Rabanan] ... a Sefer [Torah, Nevi'im or Kesuvim], [Stam] hands [that have not been guarded], a Tevul Yom (in Shabbos, the Gemara deletes this from the Mishnah, for it is mid'Oraisa), food or Kelim that became Tamei through liquids.

Answer #2 (Rava): Even regarding Chulin, the knife would not be Tamei - nothing it touched could Metamei it!

If it touched the meat - food is not Metamei a Keli!

If it touched the needle - a Keli [that is not an Av ha'Tum'ah] is not Metamei a Keli! (Therefore, we may not infer that Tum'ah of Kelim does not apply in the Mikdash.)

Question: What is the status of the needle?

Answer #1: It is Safek Tamei.

Rejection: R. Elazar or R. Yosi b'Rebbi Chanina taught that Chachamim did not decree about Safek spit in Yerushalayim [lest it is from a Zav, and hence an Av ha'Tum'ah]; the other taught that Chachamim did not decree about Safek Kelim in Yerushalayim!

Answer #2 (Rav): Someone lost a needle that was Tamei Mes, and recognized it in the meat.

Answer #3 (R. Yosi bar Avin): The case is, the cow came muzzled from outside Yerushalayim (surely, it swallowed the needle outside - nevertheless, we are lenient like the law of Safek Kelim in Yerushalayim).

(R. Elazar or R. Yosi b'Rebbi Chanina): Chachamim did not decree about Safek spit in Yerushalayim;

(The other of R. Elazar and R. Yosi): Chachamim did not decree about Safek Kelim in Yerushalayim.

Questions: We already know both of these from Mishnayos!

Question #1 (Mishnah): All spit in Yerushalayim is Tahor, except for the upper market (Tamei people used to gather there to avoid being Metamei Tehorim).

Answer: The Amora is Metaher even if we know that a Zav passed through the area where the spit was found.

Question #2 (Mishnah): All Kelim in Yerushalayim on the path people use to descend to the Mikveh are Temei'im (we assume that the owner was taking them to immerse them and dropped them).

Inference: Kelim found anywhere else are Tehorim!

Answer - counter-question (Seifa): Kelim on the path ascending from the Mikveh are Tehorim.

Inference: Kelim found elsewhere are Temei'im!

Conclusion: [The inferences contradict one another - the Amora needed to teach that the inference from the Reisha is correct (Safek Kelim are Tehorim);

The inference of the Seifa only excludes Kelim found on a path people take to and from the Mikveh (such Safek Kelim are Tamei. R. Chananel - the Amora also teaches that only in Yerushalayim Safek Kelim are Tehorim.)

Question: Rav says that the Mishnah discusses one who lost a needle that was Tamei Mes, and recognized it in the meat;

We learned from "Ba'Chalal Cherev" that a sword [or any metal Keli that touched a Mes] becomes like a Mes - [mid'Oraisa,] the needle is Metamei even people and Kelim!

Answer #1 (Rav Ashi): We must say that the Azarah is a Reshus ha'Rabim regarding Tum'ah; any Safek Tum'ah in Reshus ha'Rabim is Tahor.

Inference: If the Safek was in Reshus ha'Yachid, it would be Tamei.

Question: [The knife that might have touched] the needle is Ein Bo Da'as Lish'ol (it is incapable of telling us what happened) - if such a thing became Safek Tamei, it is Tahor even in Reshus ha'Yachid!

Answer: The Safek arose through a person [who cut with the knife];

(R. Yochanan): We ask [Beis Din; alternatively, we are stringent] about a Safek that came through a person, even regarding a Keli resting on the ground.