1)

(a)How can Rav Nechemyah possibly permit fruit that is returned to its original place, even if it was returned deliberately - considering that Rebbi Nechemyah and Rebbi Eliezer ben Ya'akov both expressly permit fruit that is returned to its Techum, only on the condition that it was returned be'Shogeg (but not be'Meizid).

(b)According to the way the Gemara amends the Beraisa - the Tana Kama only forbids the fruit be'Meizid, in its new place, but not if it was returned to its original one (where it reverts to its original Techum, even if it was returned be'Meizid); whereas Rebbi Nechemyah forbids all cases of be'Meizid - whether it was taken out be'Meizid, or returned be'Meizid.

(c)The Gemara then suggests that according to both Tana'im, if the fruit was returned deliberately, it may not be carried outside four Amos. Their Machlokes concerns carrying the fruit more than four Amos (i.e. whether they lose their Techum on Yom-Tov) or not: the Tana Kama gives the fruit two thousand Amos if they were taken be'Shogeg outside their Techum, whereas Rebbi Nechemyah gives them only four Amos (even though they were taken out be'Shogeg).

(d)This contention (based on the premise that both Tana'im agree that, by all cases of be'Meizid, the fruit loses its Techum) is however, refuted - on the basis of the Seifa of the Beraisa, where Rebbi Nechemyah and Rebbi Eliezer ben Ya'akov say 'Le'olam Asurin Ad she'Yuchzeru li'Mekoman Shogegin' - from which we can infer that, the Tana Kama permits even Meizidin, as well.

2)

(a)If one does not know exactly where the Techum Shabbos ends - one simply counts two thousand medium-size footsteps.

3)

(a)In the case of a large house of more than two thousand Amos, the entire house is considered like four Amos - only because he had acquired his place of residence in a walled area before Shabbos, unlike in our case, where it only became walled during of Shabbos, after the gentiles fenced it.

(b)True, Raban Gamliel rules in our Mishnah that someone who was forcibly taken to a large enclosure outside his Techum, may walk the entire area, even if it is more than two thousand Amos long (despite the fact that he did not acquire his place of residence there before Shabbos entered), but that is because outside the Techum, a person is restricted to four Amos, so we give the enclosure a Din of four Amos; whereas in our case (where the non-Jews made a fence on Shabbos), where there is no Din of four Amos, it is necessary to acquire his place of residence within its walls before one can be permitted to walk the entire area.

(c)Within two thousand Amos, he is allowed to carry in any way - whereas outside two thousand Amos, he is only permitted to carry by throwing.

(d)Rav Huna only permits any form of carrying within an area of four Amos.

4)

(a)Rav Huna does not permit throwing even beyond two thousand Amos - because he is afraid that, once someone is permitted to throw there, he will also walk there.

(b)Nor does Rav Huna permit throwing even within two thousand Amos - because there is no form of barrier in between them, and if he is permitted to throw in the one, there is nothing to stop him from throwing into the other.

(c)Yes! Rav Nachman makes a distinction between carrying and throwing: He forbids carrying beyond two thousand Amos (since he also forbidden to walk there), but he permits throwing there.

5)

(a)Rav Nachman told Rav Huna not to argue with Shmuel in this point because he has the support of a Beraisa.

(b)The Beraisa permits someone whose Eruv finished in the middle of the town, to carry in the entire town, even though he is forbidden to walk there. Now what can 'carry' possibly mean if not throwing?

(c)'al Yedei Meshichah' - means that even though he is forbidden to throw beyond two thousand Amos from inside his Techum to the outside (even by means of throwing), he is permitted to carry from outside the Techum to inside, (even by means of pulling). Why is that? Because the decree that he might also walk out of the Techum is not applicable in this case.

6)

(a)The Gemara amends Rav Huna's statement to read that if someone's Eruv ends in the middle of a courtyard, then he may walk up to that point (omitting the word 'only'). And the Chidush is - that we permit him to walk the entire Chatzer and do not forbid him to carry even in the half that is covered by his Eruv, for fear that he may come to carry in the other half.

(b)When Rav Nachman, claiming that Rav Huna will agree with him, states that if his Eruv ends on a roof, he has the whole house - he means that if his Eruv terminates at the end of the courtyard, at the point where the house begins, even Rav Huna will agree that he is even permitted to throw into the house. This is because it speaks when the outer wall of the house is broken, so that the outer edge of the roof will serve to remind him not to carry into the house.

(c)The Gemara thinks that Rav Nachman and Shmuel, who do not decree throwing from within one's Techum to beyond it, because he may come to walk there, hold like Raban Gamliel and Rebbi Elazar ben Azaryah, who do not decree walking in a walled enclosure, because one may come to walk in an enclosure without walls; and Rav Huna who does decree throwing from within one's Techum to beyond it, follows the opinion of Rebbi Yehoshua and Rebbi Akiva, who decree walking in a walled enclosure.

(d)The Gemara however, refutes this contention, on the grounds that ...

1. ... Raban Gamliel and Rebbi Elazar ben Azaryah may well not decree a walled enclosure because of one without walls (since these are two different cases); it does not however follow, that they will agree with Rav Nachman and Shmuel, who do not even decree throwing outside his Techum, because (in this same case) he may come to walk there. It is possible that there, they will agree with Rav Huna.

2. ... who said that Rebbi Yehoshua and Rebbi Akiva's reason is because they issue a decree, forbidding the one because of the other? Maybe their reason is because they only consider a domain as if it was four Amos square (the reason of Raban Gamliel and Rebbi Elazar ben Azaryah lenient view) when they acquired Shevisah in it before Shabbos entered, but once Shabbos arrives, we reckon the area for what it is. That is why, in our Mishnah, where the gentiles forcibly took him outside his Techum to an enclosure, they forbid walking beyond four Amos. It does not however, follow that when it comes to throwing beyond four Amos, they will not take a more lenient view (like the opinion of Rav Nachman and Shmuel); and similarly, they will agree with Rav Nachman, who permits throwing even beyond two thousand Amos in a Reshus ha'Yachid which gentiles fenced in on Shabbos.

7)

(a)Rebbi Zeira holds that even Shmuel will agree that, as long as the ship is moving, he may walk the entire ship (like Raban Gamliel) - because, since before he has had a chance to walk the four Amos that he would normally be permitted to walk, the ship moves him beyond that point, the whole boat becomes his four Amos (Ritva).

(b)If the walls of the ship broke (so that they are no longer ten Tefachim tall), or if one jumped from one boat to another (where he did not acquire his Shevisah before Shabbos), then according to Rabah, he will be forbidden to walk more than four Amos; according to Rebbi Zeira, he will be permitted.

(c)Rebbi Zeira does not want to learn like Rabah - because in his opinion, the Mechitzos of a boat serve principally, to keep the water out, and not to serve the boat itself.

(d)Rabah does not want to learn like Rebbi Zeira - because Rebbi Zeira is speaking when the boat is moving, whereas the Tana'im in our Mishnah argue when the boat is stationary, when Rebbi Zeira's explanation is inadequate. (As a matter of fact, all the Tana'im agree, says Rabah, that, when the boat is moving, one may walk the entire boat - for the reason given by Rebbi Zeira).