Eruvin 36a

עירובין ל״ו ע״א

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Topic

Doubts and חזקות in עירוב: contradictions in רבי מאיר and רבי יוסי, the limits of ספק עירוב כשר, and status during בין השמשות

Overview

The amud opens with רבא explaining why רבי מאיר is lenient in one doubt about טומאה but strict about a doubtful עירוב: the lenient case has two חזקות, the עירוב case only one. The גמרא then finds a similar contradiction in רבי יוסי and gives three answers. First, טומאה is rooted in the תורה, while for רבי יוסי תחומין are only דרבנן. Second, the lenient ruling is really a tradition he reported from his teacher. Third, רבא says the impure person keeps his חזקה of טומאה, because the מקוה was never measured. A ברייתא then limits ספק עירוב כשר to a doubt about WHEN a known change happened, and the גמרא corrects its wording about produce to a case of mixing. Next come cases about status at twilight. A pure loaf that cannot be identified is no עירוב, because neither loaf can be eaten before שבת. A loaf that is חול today and הקדש tomorrow stays חול at twilight, while the reverse case stays הקדש. Finally, from a משנה about a טבול יום flask, רבא concludes that the עירוב acquires at the end of the day.

Opening lines

The steps (27)

1. Resolutionרבא: Two presumptions there, only one here
2. Challengeרבי יוסי seems to contradict himself
3. ResolutionImpurity is different because it is rooted in the תורה
4. ChallengeBut שבת is also from the תורה
5. Resolutionרבי יוסי holds שבת limits are rabbinic
6. ResolutionOne ruling is his own, the other is his teacher's
7. ProofThe משנה's wording supports the second answer
8. Resolutionרבא: The impure person keeps his status
9. ChallengeWhy not keep the מקוה in its valid status?
10. ResolutionThe מקוה was never measured
11. StatementA ברייתא defines a valid doubtful עירוב
12. StatementA doubt from the start is not a valid עירוב
13. ChallengeWhy treat תרומה and untithed produce differently?
14. ResolutionChange the case: the produce may have become mixed
15. QuestionTwo loaves, one pure, and nobody knows which
16. QuestionThe question works even for רבי מאיר
17. QuestionThe question works even for רבי יוסי
18. Responseרב הונא answers: the עירוב is invalid for everyone
19. Questionרבא asks about a loaf that becomes הקדש at nightfall
20. Responseרב נחמן: this עירוב is valid
21. Questionרבא asks about the reverse case
22. Responseרב נחמן: this עירוב is invalid
23. Challengeרבא asks: what is the difference?
24. Resolutionרב נחמן: a doubt does not change the loaf's status
25. StatementA משנה about a flask that is a טבול יום
26. StatementUsing the same flask for an עירוב does not work
27. Conclusionרבא: the עירוב acquires at the end of the day