Question: He should establish the Mishnah to discuss Chulin Al Taharas Terumah, so the Mishnah can be like R. Yehoshua!

Answer: The Mishnah discusses meat. Terumah does not apply to meat. (Meat Al Taharas Terumah is meaningless.)

Question: The Mishnah discusses Chayos, which cannot be Korbanos! (Meat of Chayos 'Al Taharas Kodesh' should be meaningless!)

Answer: Since people can confuse meat of Chayos and Behemos, Al Taharas Kodesh applies to both. One would never confuse meat and Peros.

(Ula): Our colleagues say that the Mishnah discusses Chulin Al Taharas Kodesh, and it is unlike R. Yehoshua. I say that it can even be like R. Yehoshua!

R. Yehoshua teaches that even something Al Taharas Terumah can become a Shelishi, and all the more so something Al Taharas Kodesh, which is more stringent!

Question: Who are the colleagues Ula alluded to?

Answer: He alluded to Rabah bar bar Chanah;

(Rabah bar bar Chanah): R. Eliezer and R. Yehoshua argued as follows:

R. Eliezer: We find that one who eats food becomes more Tamei than the food itself. One who touches the Neveilah of a Tahor bird does not become Tamei, but if he eats it, he and his clothes become Teme'im when he swallows it;

We should say that if one eats a Rishon, Sheni or Shelishi, he becomes at least as Tamei as what he ate!

R. Yehoshua: We cannot learn from a Tahor Neveilah bird, for that is a Chidush;

Rather, regular Tamei food is more severe than the one who eats it. Tamei food the size of an egg can be Metamei other foods, but one who eats Tamei food does not become Tamei until he eats half a loaf (the volume of two eggs)!

R. Eliezer: We do not learn (the degree of) Tum'ah from the quantity required to be Metamei;

Also, you contradict yourself! You say that one who eats a Rishon becomes a Sheni. This is like your rule that one does not become as Tamei as what he eats;

You also say that one who eats a Sheni becomes a Sheni!

R. Yehoshua: A Sheni is different, for a food that is a Sheni can make another food a Sheni through a liquid (e.g. if the second food is wet).

Version #1 (Rashi) R. Eliezer: If so, you should also say that one who eats a Rishon becomes a Rishon, for a food that is a Rishon makes a liquid a Rishon!

Version #2 (Tosfos) R. Eliezer: This does not show that a Tum'ah can impart the same Tum'ah to another food. The liquid becomes a Rishon (this is a special decree, due to liquids that are an Av ha'Tum'ah), and the liquid makes the second food a Sheni! (end of Version #2)

(Mishnah): Anything that is Posel Terumah, it makes a liquid a Rishon, except for a Tevul Yom (one who was Tamei and immersed today. His Taharah is not complete until nightfall).

Also, why do you say that one who eats a Shelishi becomes a Sheni?

R. Yehoshua: (Rashi - a special decree makes a liquid a Rishon. We do not learn from it that one who eats a Rishon becomes a Rishon.) I said that one who eats a Shelishi becomes a Sheni only regarding Chulin Al Taharas Terumah, which is not considered guarded regarding Kodshim. (Therefore, we suspect that perhaps he ate a Sheni.)

(R. Asi citing R. Yochanan): If one eats Chulin Al Taharas Kodesh that is a Shelishi, he becomes a Sheni regarding Kodesh.

Question (R. Zeira - Mishnah (33b) - R. Yehoshua): If one eats a Shelishi he becomes a Sheni regarding Kodesh, but not regarding Terumah. The case is, he ate Chulin Al Taharas Terumah.

Inference: This applies only to Chulin Al Taharas Terumah, but not to Chulin Al Taharas Kodesh!

Answer (R. Asi): No. R. Yehoshua teaches a bigger Chidush, that it even applies to Chulin Al Taharas Terumah (and all the more so, to Chulin Al Taharas Kodesh).

Question: R. Yehoshua said that he becomes a Sheni only because the guarding of Terumah is insufficient regarding Kodshim!

Answer: Rabah bar bar Chanah said in the name of R. Yochanan that R. Yehoshua said this. R. Asi holds that R. Yochanan never said this.

(Ula): If one eats a Shelishi of Chulin Al Taharas Terumah, he becomes forbidden to eat Terumah.

Question: The Mishnah teaches that. Why must Ula teach it?

(Mishnah): If one eats a Shelishi, he becomes a Sheni regarding Kodesh, but not regarding Terumah. This applies to Chulin Al Taharas Terumah.

Inference: He is not a Sheni regarding Terumah, but he is a Shelishi (i.e. he may not eat it).

Answer: One might have thought that he is neither a Sheni nor a Shelishi regarding Terumah;

Since the Mishnah said he is a Sheni regarding Kodshim, it said that he is not a Sheni regarding Terumah (for parallel structure).

Ula teaches that this is not so.

Question (Rav Hamnuna - Mishnah): If Chulin is a Rishon, it is Tamei. It is Metamei food that it touches;

A Sheni is Posel. It does not make Tamei;

A Shelishi may be eaten with Terumah mixed in. (Surely, it was guarded like Terumah since he planned to mix it with Terumah).

(Summation of question): If one who eats a Shelishi becomes a Shelishi, why is this permitted?

Answer: The case is, he mixes less than a k'Zayis of Terumah in the volume of half a loaf. (Therefore it is not treated as Terumah, rather, like regular Chulin. A Shelishi does not apply to Chulin, so it is Tahor.)