Answer #2 (Rav Ashi): The Mishnah discusses a valley enclosed by walls.

(Ula): If a Karfef (a Chatzer without houses open to it) more than Beis Sa'atayim (5000 square Amos) was surrounded by a wall, but not for the sake of dwelling, [it is forbidden to carry four Amos inside, yet] one who throws to it [from Reshus ha'Rabim] is liable;

The same applies even if it is more than a Beis Kor (75,000 square Amos) or two.

Question: What is the reason?

Answer: The Karfef has a proper wall, just it lacks residents [it is a Reshus ha'Yachid mid'Oraisa, mid'Rabanan we are stringent to consider it a Karmelis].

Question: We understand why Rav Ashi did not answer like Ula (see (d) below);

Why didn't Ula answer like his teaching?

Answer: He holds that the Tana would not call it 'valley' if it had walls, rather, 'Karfef'.

Rav Ashi holds that since the Tana called it Reshus ha'Yachid, surely it is Reshus ha'Yachid mid'Oraisa.

(Beraisa): [A sea, valley, platform,] or Karmelis...

Question: The things listed beforehand are also Karmelis!

Answer (Rav Dimi): 'Karmelis' includes a corner next to Reshus ha'Rabim (e.g. someone's property bordered Reshus ha'Rabim, and his house jutted out - he allowed Reshus ha'Rabim to 'annex' the property next to his house)

Even though sometimes it is crowded in Reshus ha'Rabim and people enter this area, since it is inconvenient (one must return to the main road when he encounters the house) it is [not Reshus ha'Rabim, only] Karmelis.

(Rav Dimi): Between the pillars [in the market, where merchants hang their wares] is a Karmelis.

Question: What is the reason?

Answer: Even though many people go there, since it is inconvenient, it is [not Reshus ha'Rabim, only] Karmelis.

(R. Zeira): The platform in front of the pillars is a Karmelis.

Rav Dimi said that between the pillars is a Karmelis, all the more so he holds that the platform is a Karmelis;

Version #1: R. Zeira said that the platform is a Karmelis, but he would hold that between the pillars is not so inconvenient, it is [Reshus ha'Rabim,] not Karmelis.

Version #2: Between the pillars is Reshus ha'Rabim, because sometimes people walk there.

(Rabah bar Shila): If one threw something [four Amos] in Reshus ha'Rabim at (and it stuck to) the side of a brick standing upright in Reshus ha'Rabim, he is liable (it is as if rested on the ground below);

If it landed on top, [this is not considered Reshus ha'Rabim], he is exempt.

(Abaye and Rava): This is only if the brick is [at least] three Tefachim tall - if not, many people trample on it (even the top is [Batul to] Reshus ha'Rabim);

Regarding prickly bushes, even if they are not three Tefachim [they are not Reshus ha'Rabim, for people do not step on them].

(Chiya bar Rav): Prickly bushes are Reshus ha'Rabim [people wearing shoes step on them], but excrement is not (people do not walk on it).

(Rav Ashi): Even excrement is Reshus ha'Rabim (anything less than three tall is Batul to Reshus ha'Rabim, even if people do not walk on it).

(Rav Dimi): Karmelis does not apply to an area less than four [by four Tefachim].

(Rav Sheshes): Karmelis applies up to 10 [Tefachim above the ground].

Question: What does this mean?

Suggestion: Karmelis applies only if there is a wall 10 Tefachim tall.

Rejection: Rav Gidal taught that if the interior of a house is less than 10, and the roof completes the Shi'ur of 10, one may carry anywhere on the roof (it is Reshus ha'Yachid), one may not carry four Amos inside (it is Karmelis).

Answer: It means, until 10 Tefachim off the ground is Karmelis, above is not (it is Makom Petur), like Shmuel taught to Rav Yehudah.

(Shmuel): No laws of Shabbos apply above 10 Tefachim.

Question: What does Shmuel teach?

Suggestion: He teaches that Reshus ha'Yachid does not apply above 10.

Rejection: Rav Chisda taught, if one erects a beam in Reshus ha'Yachid with a basket on top, even if it is 100 Amos tall, one who throws something into it from Reshus ha'Rabim is liable, for Reshus ha'Yachid extends to the sky.

Answer #1: He teaches that Reshus ha'Rabim does not apply above 10.

Rejection: We already learn this from a Mishnah!

(Mishnah): If one threw something four Amos [in Reshus ha'Rabim] at (and it stuck to) a wall:

If this was above 10 Tefachim [he is exempt], it is as if he threw in the air (i.e. and it never landed);

If this was below 10 Tefachim [he is liable], it is as if he threw on the ground.

Answer #2: He teaches that Karmelis does not apply above 10.

Chachamim gave the leniencies of Reshus ha'Yachid and Reshus ha'Rabim to Karmelis:

It has the leniency of Reshus ha'Yachid, that it does not apply to an area less than four by four Tefachim;

It has the leniency of Reshus ha'Rabim, that it does not apply above 10.

(Rav Gidal): If the interior of a house is less than 10, and the roof completes the Shi'ur of 10, one may carry anywhere on the roof, one may not carry four Amos inside.

(Abaye): If one dug out a cavity four by four in the floor, so that the interior height of the house in that place is 10, it is permitted to carry in the entire house.

Question: What is the reason?

Answer: (The place of the cavity is a proper Reshus ha'Yachid (it need not be adjacent to the walls),) the rest of the house is like Chorei [holes coming out from] Reshus ha'Yachid, they are like Reshus ha'Yachid:

Chorei Reshus ha'Yachid are like Reshus ha'Yachid;

(Abaye): Chorei Reshus ha'Rabim are like Reshus ha'Rabim;

(Rava): They are not like Reshus ha'Rabim.

Question (Rava, against Abaye): Rav Dimi taught that 'Karmelis' (in the Beraisa 6A) includes a corner next to Reshus ha'Rabim - it is Chorei Reshus ha'Rabim, according to you it is like Reshus ha'Rabim!

Answer (Abaye): It is not like Reshus ha'Rabim because it is inconvenient to use them (walk there) - regular Chorei Reshus ha'Rabim are convenient to use.

Question (against Abaye - Mishnah): If one threw something four Amos at a wall:

If this was above 10, it is as if he threw in the air; if this was below 10, it is as if he threw on the ground.

Question: When it was below 10, why is he liable - it was not Nach [outside of four Amos, for it bounces back]!

Answer (R. Yochanan): The case is, he threw a fat fig cake [it stuck to the wall].

Summation of question: According to Abaye, R. Yochanan could have established the Mishnah to discuss a pebble or object that landed in a hole in the wall, i.e. Chorei Reshus ha'Rabim!

Answer #1 (Abaye): A pebble or object would probably bounce off and not land in the hole.

Answer #2 (Abaye): The Mishnah discusses a wall without a hole.

Question: What is the source to say this?

Answer: The Reisha says, if it was above 10, it is as if he threw in the air - if there is a hole [and it landed inside], this is not like throwing in the air [it is Chorei Reshus ha'Yachid, he is liable]!

Suggestion: Perhaps the case is, the wall is not four by four (therefore, above 10 is not Chorei Reshus ha'Yachid)!

Rejection: Rav Yehudah taught that if one threw above 10 and it landed in a hole of any size [less than four by four], R. Meir and Chachamim argue about whether or not he is liable:

R. Meir says [regarding Mezuzah, and would also say here] Chokekim Lehashlim (if there is a small hole in something thick, we consider it as if the entire thickness was carved out - therefore, if the wall is four by four, it is as if the hole is four by four);

Chachamim do not say Chokekim Lehashlim.

Since we may assume that our Stam Mishnah is like R. Meir, it must be that there is no hole.

(Rav Chisda): If one erects a beam in Reshus ha'Yachid with a basket on top, even if it is 100 Amos tall, one who throws something into it from Reshus ha'Rabim is liable, for Reshus ha'Yachid extends to the sky.

Suggestion: This is like Rebbi:

(Beraisa - Rebbi): If one threw something [in Reshus ha'Rabim] and it landed on a ledge of any size, he is liable;

Chachamim exempt.

Rejection (Abaye): No, all agree to Rav Chisda's law in Reshus ha'Yachid - the Beraisa discusses a tree in Reshus ha'Yachid, its foliage hangs in Reshus ha'Rabim, the thrown object landed on the foliage;

Rebbi applies the status of the trunk (i.e. a Reshus ha'Yachid that is four by four) to the foliage, Chachamim do not.