Eruvin 8b

עירובין ח׳ ע״ב

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Topic

Fixing a מבוי for carrying: the centipede alley, placing the קורה on uneven walls, and using the space under the קורה

Overview

This amud finishes one discussion and then opens several new ones about fixing a מבוי so you may carry in it. First, the גמרא explains why רב's ruling about a courtyard breached on two sides is not redundant after the תוספתא. According to רבה, the תוספתא only shows liability for throwing into the courtyard, and רב adds that you may also carry inside it. Next comes a מבוי shaped like a centipede (נדל). אביי's solution is rejected by רבא, who rules according to רב: a צורת הפתח goes on one side of the small alleys, and a לחי or קורה is enough on the other side. Then a chain of teachers named כהנא rules on an alley with one long wall and one short wall. A small difference allows a diagonal קורה. רבא always requires the beam at the end of the short wall, because he holds that a קורה is a היכר and not a מחיצה. רב כהנא adds that a diagonal over ten אמות is invalid according to everyone. The גמרא then asks whether you may use the space under the קורה, brings a dispute of three against three, and shows that the dispute can fit either view of what a קורה is. Finally, רב חסדא and רבא argue about a קורה resting on pegs outside the alley walls. רב אדא בר מתנה begins to challenge רבא from a ברייתא that continues on the next amud.

Opening lines

The steps (23)

1. ResolutionFinishing the answer: רב adds the case where the breaches are opposite each other
2. ChallengeAccording to רבה, רב's ruling seems to repeat the תוספתא
3. ResolutionThe תוספתא is about throwing; רב adds permission to carry
4. Statementאביי's ruling on an alleyway shaped like a centipede
5. Challengeרבא asks: אביי's ruling only fits שמואל, and even then the doorway-form is unnecessary
6. Challengeרבא's second challenge: practice in נהרדעא followed רב
7. Statementרבא's own solution for the centipede alley
8. StatementAlley with one long wall and one short wall
9. Statementרבא disagrees: always at the end of the short wall
10. Questionרבא sets up his reasoning: what is the purpose of a crossbeam?
11. ResponseA crossbeam is a visible marker, and a diagonal one is not visible enough
12. ResponseThe other side's reason: a beam counts as a wall
13. Statementרב כהנא limits the diagonal beam to ten אמות
14. QuestionNew question: may one carry under the beam?
15. StatementThree permit and three forbid using the space under the beam
16. QuestionSuggestion: the argument depends on sign versus wall
17. RejectionEveryone may agree the beam is a marker, and the argument is about who the marker is for
18. RejectionEveryone may agree the beam is a partition, and the argument is about which edge counts
19. StatementEveryone agrees the space between the side posts is forbidden
20. QuestionWhat if the beam rests on pegs on the outside of the alley walls?
21. Responseרב חסדא answers: the two opinions flip for a beam on outside pegs
22. Rejectionרבא disagrees: the beam must sit on top of the alley walls
23. Challengeרב אדא בר מתנה begins to challenge רבא from a ברייתא