(Mishnah): There are two appearances of Tzara'as, which are four.

(Beraisa #1 - R. Yosi): Yehoshua the son of R. Akiva asked him "why did they say that there are two appearances of Tzara'as, which are four"? R. Akiva said, if not, what should they say?

Yehoshua: They should say, from Karom (like an egg shell) and above (whiter) is Tamei!

R. Akiva: This teaches that if [a Kohen] is not expert in [the appearances] and their names, he may not inspect Nega'im.

Question: What is the source that [appearances] join with one another?

Answer #1 (R. Mana): Chachamim counted [the appearances] as two, and they counted them as four. Just like two join with each other (below we learn from verses that Seis joins with Baheres), even [all] four join with one another. (Karom joins with its "Av", i.e. Seis (like clean wool), and Sid (like plaster) joins with its Av, i.e. Baheres (like snow).)

Answer #2 (R. Lazar citing R. Avin): If [an appearance, e.g. Seis] joins with b'Eino Mino (Baheres, which is in a different family), all the more so Min joins with Mino (within its family)!

Answer #3 (R. Yosi bei R. Bun): It is not written 'v'Hayu', rather, "v'Hayah" (singular). This teaches that [different appearance are considered like one, i.e.] they join with each other!

Answer #4 (Chizkiyah - Beraisa): It is not written 'l'Nig'ei Tzara'as', rather, "l'Nega Tzara'as." This teaches that they join with each other!

Note: Chizkiyah holds that all four appearances join, unlike we said above (R. Shimshon Nega'im 1:1, Rambam according to Chidushei R. Meir Simchah.)

(Beraisa #2) Question (Yehoshua, to R. Akiva): They should say "like an egg shell and above is Tamei, and they join", and they need not say "appearances of Tzara'as are two that are four"!

Answer (R. Akiva): This teaches that [the appearances] are not one above the other (in whiteness. Rather, Sid and Seis are different appearances of equal whiteness.)

Suggestion: [Perhaps] they are one above the other (Seis is whiter than Sid)!

Rejection: If so, it turns out that you say that what is weaker [than Seis] is Tamei (i.e. Sid), and what is weaker than what is weaker (Karom) is Tamei, and the Torah said "v'Hinei Kehah ha'Nega" - what is weaker is Tamei, but what is weaker than what is weaker is Tahor! (Rather, Sid is as white as Seis, so Karom is weaker than Seis.)

This is like R. Chaninah said, [a parable for appearances joining is] two kings and [their] two nobles. This king is greater than this king, and this noble is greater than this noble, but this noble is not greater than this (the other) king, and this noble is not greater than this king (rather, they are equal, i.e. Sid and Seis).

(Shmuel): [A parable for appearances joining] is two kings and [their] two messengers. This king is greater than this king, and this messenger is greater than this messenger, but this messenger is not greater than this king.

Note: Shmuel holds like R. Chaninah. He merely gave a different parable.

(R. Chanina citing Rav Acha bar Achva): [A parable for appearances joining] is a king and his chief general, and the Mishneh l'Melech and the Reish Galusa.

R. Lazar bei R. Yosi (to R. Yosi): A Beraisa teaches that they are not one above the other!

(Beraisa): Regarding Seis, an appearance that is weaker than [Karom, i.e.] what is weaker than itself is Tahor, yet it has a secondary appearance - Baheres, that what (Karom) is weaker than (Seis) what is weaker than itself is Tamei, all the more so it has a secondary appearance (Sid, which is Tamei! This is like we said above, that Karom is called weaker than Sid, and not weaker than weaker than it, for Sid is not weaker than Seis.)

Objection (R. Yosi): Look what you say! [Baheres] has a Shelishi (third level Tamei appearance, i.e. Karom, which is weaker than Seis, which is weaker than Baheres. All the more so it has a secondary (Tamei appearance, i.e. Sid, which is weaker than Baheres! Why must you learn from Seis? We explained this like Chidushei R. MEIR SIMCHAH.)

Answer (R. Lazar): Why do you explain the Beraisa so? [Rather,] Baheres, what is weaker than what is weaker than itself is Tamei - [what is weaker] refers to Seis, that in the family of Seis is Karom. (Even though Karom is the third from Baheres, it is not in its family. We explained this like RIDVAZ.)

(Beraisa): "Seis" is Seis. "Baheres" is Baheres. "Sapachas" is secondary to Seis. "U'Mar'eha Amok Min ha'Or" is secondary to Baheres.

Seis is an expression of elevated, like the shade appears higher than what is in sunlight (which looks deeper. I.e. it appears higher than Baheres, for it is dimmer.)

"Amok" is an expression of depther than the appearance of sunlight, which is deeper than the shade. (Therefore, "ba'Baheres u'Mar'eha Amok Min ha'Or" alludes to another Tamei appearance; it appears deeper than Baheres, for it is dimmer than it.)

Sapachas is an expression of secondary - "Sapcheni Na El Achas ha'Kehunos..."

(R. Lazar): This is the opinion of R. Yishmael and R. Akiva, but Chachamim say that Seis and Baheres are one (for both, we learn their secondary appearances from Sapachas, which is written between them). Sapachas teaches that there is a secondary appearance for this one and for this one.

Support: A Mishnah teaches so! If [a Nega dimmed, i.e. it was Seis and] it became Mispachas of Seis, or [it was Baheres and] it became Mispachas of the strong appearance...