Taharos, Chapter 6, Mishnah 1. This perek takes up the subject of reshuyos, domains, and examines them far more intensively than before. The background principle is familiar: a safek tumah that arises in a reshus hayachid, a private domain, is ruled tamei, while the identical safek arising in a reshus harabim, a public domain, is ruled tahor. Our mishnah asks what happens when the domain itself will not hold still, and then what happens when the person will not hold still.
A place whose status keeps changing
"Makom shehayah reshus hayachid vena'asah reshus harabim": a place that had the status of a private domain and then became a public domain. How does such a thing happen? In one of two ways. Sometimes it is a matter of the seasons: through the rainy winter months the spot is untraveled and functions as a private domain, while in the summer the public streams across it and it functions as a public domain. Sometimes it is a matter of ownership: property that had been open to the public was sold, or property that had belonged to an individual passed into public use.
"Chazar vena'asah reshus hayachid": and then it reverted to its earlier standing, once again for either of those reasons, the turn of the season or a commercial transaction. So how are sfeikos of tumah judged on a piece of ground that keeps flipping back and forth?
The answer is refreshingly simple: we judge it by what it is at the moment the safek arises. "Keshehu reshus hayachid, sfeiko tamei; keshehu reshus harabim, sfeiko tahor". While it stands as a private domain, a doubt there is ruled tamei; while it stands as a public domain, a doubt there is ruled tahor. The place's history is irrelevant; only its present status counts.
The dangerously ill man carried from domain to domain
"Hamesukan birshus hayachid vehotzi'uhu lirshus harabim": here is an intriguing case. A man is deathly ill, so far gone that he has lost consciousness, and we cannot determine whether he is still alive or has already died. Since a meis conveys tumah, the doubt about his life is at the same time a doubt about whether those with him have become tamei.
He begins in a reshus hayachid. Picture a caravan, or a sick man borne along on camelback: he is carried out from the private domain, taken through a public domain, and then brought into a private domain once more. This is a striking twist on the previous case. There, the domain changed while the situation stayed put; here, the domains stand still and the one man in question moves in and out of them.
The Chachamim find nothing remarkable in this at all and apply the ordinary rules of safek: "keshehu birshus hayachid, sfeiko tamei; keshehu birshus harabim, sfeiko tahor". For as long as he is in the private domain the doubt is ruled tamei, and for as long as he is in the public domain the doubt is ruled tahor. That is the whole of it.
Rebbi Shimon, however, sees a genuine difficulty here. His ruling is "reshus harabim mafsekes", the public domain interrupts. His reasoning rests on the reality of the case: one person, who is by definition either living or dead, is being carried from place to place. It makes no sense to declare that inside the private domain he counts as a source of tumah, that upon being brought into the public domain he no longer does, and that upon returning to a private domain he does again. Whether he has died is not affected by where his stretcher happens to be. The interval of public domain through which he was carried therefore gives us no license to reverse his status twice over, and he is judged as though he had never left the reshus hayachid at all.
The halachah, though, does not follow Rebbi Shimon. We rule as the Chachamim do: a safek tumah is decided as tahor or tamei according to whichever domain it presently finds itself in, whether it is the ground that changed status or the person who moved from one domain to another.