Taharos, Chapter 6, Mishnah 4. This chapter is built around one great divide: a safek tumah that arises in a reshus harabbim leaves a person tahor, while the identical safek in a reshus hayachid renders him tamei. Our Mishnah now asks what happens when the doubt is not a single doubt at all, but doubt layered upon doubt.
The Mishnah states the rule sweepingly: "Kol she'atah yachol leharbos sfeikos usfek sfeikos, birshus hayachid tamei, birshus harabbim tahor": however many sfeikos you are able to stack up, and even sfek sfeikos, doubled doubts, in the private domain the ruling is tamei, and in the public domain the ruling is tahor.
This is worth pausing over, because anyone who has learned the relevant sections of Yoreh Deah knows how much weight a doubled doubt normally carries. The Shach devotes a whole set of rules to sfek sfeika, the Klalei Sfek Sfeikos, and there the principle is that once a doubt rests upon another doubt we rule leniently. In the world of tumah and taharah that calculus simply does not apply. Multiplying sfeikos changes nothing. In a reshus hayachid the person remains tamei no matter how many layers of uncertainty he can assemble, and in a reshus harabbim he remains tahor.
The Chain of Sfeikos
The Mishnah asks "keitzad", how so, and answers with a case built out of doubt after doubt. A man walks into a mavoi, an alleyway, and the tumah is lying in the adjacent chatzer, the courtyard.
- "Safek nichnas safek lo nichnas": it is unclear whether he entered the courtyard at all. That is the first safek.
- Or the tumah is inside the bayis, the house, and again it is a safek whether he entered or not.
- "Afilu nichnas, safek haysah sham safek lo haysah sham": even granting that he did enter, it is a doubt whether the tumah was there at that moment.
- "Afilu haysah sham, safek yesh bah kashiur safek ein bah kashiur": even granting that it was there, perhaps the object was smaller than the minimum shiur needed to convey tumah.
- "Afilu yesh bah, safek tumah safek taharah": even granting that it had the necessary shiur, perhaps the object was never tamei in the first place.
- "Va'afilu tumah, safek naga safek lo naga": and even granting that it was genuinely tamei, perhaps he never touched it at all.
Six or seven doubts deep, and the Mishnah concludes: "sfeiko tamei". In every one of these configurations, when the setting is a reshus hayachid, the safek is resolved toward tumah.
Rebbi Elazar and the Source in Sotah
Rebbi Elazar disagrees, and his disagreement rests on where this entire body of law comes from. The whole concept of reshuyos in the realm of tumah and taharah, that a safek is treated strictly in a private place and leniently in a public place, is derived from the sotah. A sotah is a woman suspected of adultery. If we knew with certainty that she had been unfaithful she would not be a sotah at all, she would simply be an adulteress. What defines her case is the doubt: she is known to have secluded herself in a private space, and she is suspected of what happened there. Here the Torah itself presents a safek that arose in a reshus hayachid, and the Torah treats her as tmei'ah until her status is later clarified. Both sides of the machlokes in our Mishnah accept the sotah as the source of the whole system; the question is how tightly the derived law must resemble its source.
Rebbi Elazar wants the parallel to be exact: "safek bi'ah tahor, safek maga tumah tamei". Look closely at the sotah, he argues. There is no question whether she was in the room; she was certainly there. The only question is what took place while she was there. So a safek about contact, safek maga, genuinely mirrors the sotah and is therefore judged as tamei. But a safek bi'ah, a doubt over whether the person ever entered the place at all, has no counterpart in the sotah and should not be called a safek tumah in a reshus hayachid. Such a person, says Rebbi Elazar, remains tahor.
The halachah does not follow Rebbi Elazar. But he deserves credit for remarkable consistency: he holds this line again in the following mishnah, where a man is unsure which of two fields he walked into, and Rebbi Elazar once more declares him tahor because the doubt is only a safek bi'ah. For us, the ruling of the Mishnah stands: doubts may be piled as high as one likes, and in the private domain the verdict is still tamei.