tosafos tells us that if someone tells us they are a jew we follow the rov that they are telling the truth in a case where the majority of people are jews.why do we not say this is a case of kavua since the gemara in kesuvos (15a) tells us that concerning people we always use the logic of kavua.
Shmaya Ormonde, england
The Rov which Tosfos actually uses -- "Rov people who come before us and say they are Jewish are Jewish" -- is not subject to the rule of "Kol Kavu'a" since it is not based on statistics, but rather on a logical Sevara, and there is no Mi'ut Yadu'a. Therefore, it is comparable to Chazakah.
Moreover, Tosfos writes in many places that where the Mi'ut is not known in the Makom of the Keviyus, there is no Kavu'a Min ha'Torah and it is only a Gezeirah which would not apply in this case.
However, even on the "Ein Lomar" of Tosfos -- that in the case in Pesachim the Nochri was believed to eat Korban Pesach for there were Rov Jews in that place (Eretz Yisrael) -- the rule of Tosfos in Kesuvos does not apply. Tosfos in Kesuvos does not argue on the Gemara. The Gemara there writes that when the man went to the woman, we do follow Rov. Tosfos writes only that if, at the time that we have a Safek, the element which was "Poresh" has already gone back ("Hadrei l'Nichusa"), then we consider the person Kavu'a and not Nayid. Therefore, in the case where someone married an unknown woman, and at a later date we want to know who that woman was, we say that at this time she is no longer "Parush" and we say "Kol Kavu'a." However, in the case of the Gemara there, where the Bo'el was "Parush" at the time in question, or in the case of Tosfos at the time that someone is claiming to be Jewish, he is definitely "Parush" and we apply the Rov.
D. Zupnik
Thank you very much for your reply regarding Yevamos 47a. Just to clarify
a couple of points:
You said that if the miut is not known the rule of kavua does not apply. When discussing the case of whether one has to woory about whether fruits that are bought in the market place have any problems of orla some poskim say that the rule of kavua applies to these fruit as the fruit in the market place is considered in the orchard. Is this not a case where the rov and the miut are not nicar and hence kavua should not apply.
I'm sorry, I Must have left out a word. The important question is if the Mi'ut is Nikar bi'Mkomo, i.e. the Makom of the Keviyus, which is the case by the fruit of Orlah.
D. Zupnik