Opinion #1 (Rav Huna citing Rav): All agree that one who throws [from Reshus ha'Yachid to Reshus ha'Rabim through Karmelis] is liable.

Explanation: All agree that the air above Karmelis is not like it is full [to say that it is as if it rests in the air].

What do they argue about? They argue about one who is Motzi (carries from Reshus ha'Yachid to Reshus ha'Rabim through Karmelis). Ben Azai exempts, and Chachamim obligate;

Ben Azai considers one who walks to be like one who does Hanachah, and Chachamim do not consider one who walks to be like one who does Hanachah.

Question (Rav Chisda, to Rav Huna): According to Ben Azai, a person is never liable for four Amos in Reshus ha'Rabim, for he is considered like one who rested every Amah (i.e. step), and he should be exempt! (In our text, this is not answered. In Tosfos' text, the Yerushalmi answers that one who jumps is liable.)

Opinion #2 (Rav Yehudah citing Rav): All agree that Motzi is exempt. All agree that one who walks is like one who does Hanachah;

What do they argue about? They argue about one who throws. Ben Azai exempts, and Chachamim obligate. Ben Azai considers the air above Karmelis as if it is full, and Rabanan do not consider the air above Karmelis as if it is full.

A Beraisa supports this one, and a Beraisa supports this one.

A Beraisa supports Rav Yehudah. If one was standing in Reshus ha'Rabim and threw into an enclosure for animals, via a Karmelis, he is liable. If he was Motzi, he is exempt. (We assume that the Stam Tosefta is like Chachamim.)

A Beraisa supports Rav Huna. If one was Motzi food and put it on the threshold, whether he later took it out [to Reshus ha'Rabim], or someone else took it out, he is exempt, for his Melachah was not done at once;

Inference: Had he done his Melachah at once, he would be liable;

Ben Azai says, even if he did his Melachah at once, he is exempt.

Question (Mishnah - R. Meir): If it was Shabbos and he was Motzi [the food...], and they said to him "this (liability for Shabbos) is different. This is due to walking, and this is liable [only] for Hanachah'';

According to Rav Huna, [the Rabanan who argue] are unlike Ben Azai. According to Rav Yehudah, they are unlike Ben Azai, and unlike Rabanan (for Rav Yehudah says that all say that one who walks is like one who does Hanachah)!

Answer (R. Chinena): Who said so [to R. Meir]? It is Chachamim, who hold [even] like Ben Azai. (He did not eat while walking. Rather, he was on the threshold, partially inside and his mouth was outside, like R. Yudan answered above (2b).)

Question (R. Yochanan): If one was standing in Reshus ha'Rabim and threw, and caught it before it landed, what is the law?

Question: Do we not learn this from a Mishnah?! If someone else caught it, or a dog caught it, or it burned [before it landed], he is exempt;

(R. Yitzchak citing R. Ze'ira): [The Mishnah] discusses one who snatched it from the air [before it completed its course], but if he [stood where it was going to land and] caught it, [the thrower] is liable. What is the difference whether it landed on the ground, or in the hand [of one who stood there and caught it? Also here, if he snatched it he is exempt, but if he caught it, he is liable!]

Answer: (They are different.) There, why is he liable? There, he threw and someone else caught. However, here, he threw and he caught. (It is as if it landed in the same place it started. This is a reason to exempt.)

Answer: It should be obvious that he is liable! If he threw with his right hand, and caught with his left hand, is he not liable, from the law of [completing Hotza'ah in the] mouth?! (Chachamim agree that he is liable, just they hold that it is not considered liability due to eating. We explained this like HA'GAON RAV C. KANIEVSKY, SHLITA);

Is the mouth not considered like another person? Here [also] his left hand is like another person!

(R. Yudan): It is obvious to R. Yochanan that if he threw with his right hand, and caught with his left hand, he is liable. He asked about one who threw with his right hand and caught with his right hand.

(Rabanan of Kisarin citing R. Shamai citing R. Acha): Even if he threw with his right hand, and caught with his left hand, he needs [to ask] whether he is liable. the Oni is Chayav [Kares if he was Mezid, Misah if he was warned, and Chatas if he was Shogeg], and the Ba'al ha'Bayis is exempt;

If you will say [that we can learn from] his mouth [we can distinguish]. His mouth, since [he is liable only after] he eats it, is like someone else. However, here, is his hand like someone else?! (Surely it is not. It is as if it landed in the same place it started, so perhaps he is exempt.)

Question (R. Mana): If so (the one who says that from the right hand to the left is liable, for it is like two people), if he was Motzi k'Grogeres with both his hands he should be exempt, for it is like two who did one Melachah!

Answer (R. Chiya bar Ada): This is "b'Asosah'' (an individual who did an Aveirah). Was it not taught that an individual who did is liable, and two or three who did are exempt?