OPINIONS: Reish Lakish says in the name of Rebbi Oshiya that dough of Terumah that was found next to a child is assumed to have become Tamei and must be burned, because of the Chazakah that children play (Metafchin) with the dough. Rebbi Yochanan disagrees and says that this is not the type of Chazakah which requires that Terumah be burned. Rather, the type of Chazakah which requires that Terumah be burned exists when the dough of Terumah was found in a house in which Sheratzim and Tzefarda'im crawl, and pieces of vermin were found in the dough. If most of the vermin in the house are Sheratzim, the Terumah must be burned.
These two cases -- dough of Terumah found next to a child and dough of Terumah found in a house with Sheratzim and Tzefarda'im -- both involve a Rov. In one case, Rebbi Yochanan maintains that the Rov is not sufficient evidence to rule that the Terumah is certainly Tamei, while in the other case he maintains that the Rov is sufficient evidence to rule that the Terumah is certainly Tamei. What is the difference between the two cases?
(a) RASHI (DH Im Rov Sheratzim) explains that the case of the Terumah found next to a child is a "Ruba d'Leisa Kaman," and the case of the Terumah found near Sheratzim is a "Ruba d'Isa Kaman."
A "Ruba d'Leisa Kaman" refers to a majority in frequency; something usually occurs in this manner. There is no tangible item in front of us, however, which presents that Rov. For example, there is a Rov that "most animals are not Tereifos." This Rov is not related to any tangible item in front of us; rather, this Rov states a fact in the frequency of the occurrence of mortal blemishes in animals (i.e. that most animals are born healthy). The Rov that most children play in dough is a "Ruba d'Leisa Kaman" because it is a fact about the play habits of children.
In contrast, "Ruba d'Isa Kaman" refers to a situation in which the Rov is physically in our presence. For example, when one piece of Tereifah meat became mixed up with two pieces of kosher meat, the Rov is in front of us. The Rov of Sheratzim is this type of Rov since, in the house in front of us, there are more Sheratzim than Tzefarda'im. This type of Rov is considered a more powerful Rov, and, according to Rebbi Yochanan, this type of Rov resolves a doubt in a manner of certainty.
(b) The RITVA offers a different explanation. The two cases of the Gemara differ in two basic ways. Did the Tamei item touch the Terumah, and was the Chazakah that the Terumah was Tahor weakened? When a child is found holding a piece of the dough, it is only assumed that the piece of dough came from the dough of Terumah. It is not known for certain that it came from the dough of Terumah. In the case of the Sheratzim, it is known that something certainly touched the dough; the only question is whether it was a Sheretz Tamei or a Sheretz Tahor. The Rov applies only when another factor is present which weakens the Chazakah. In the case of the child, the Rov cannot override the Chazakah since the very fact that the dough was touched is in question. In the case of the Sheratzim, the Rov can override the Chazakah because the Chazakah (that the Terumah was Tahor) has been weakened by the fact that something definitely touched the dough.
QUESTION: Rebbi Meir maintains that when a child is found next to dough of Terumah with a piece of dough in his hand, the dough of Terumah is Tahor. The Gemara explains that according to Rebbi Meir, although a majority (Rov) of children play (Metafchin) with everything near them while a minority (Mi'ut) of children do not, that Mi'ut combines with the Chazakah that the dough is Tahor and weakens the Rov, and thus the dough is assumed to be Tahor.
Why does Rebbi Meir need to utilize the Chazakah of the dough? Why does he not use the Chazakah of the child himself? Every person has a "Chezkas Tahor," and thus he should combine the Chazakah that the child is Tahor with the Mi'ut that some children do not play with everything around them. Accordingly, the child was never Tamei in the first place. (REBBI AKIVA EIGER)
ANSWER: The AYELES HA'SHACHAR answers that a Chazakah cannot be utilized in all situations. A Chazakah cannot be utilized when it is in direct conflict with a Rov. In the case of the Gemara, combining the "Chezkas Tahor" of the child with the Mi'ut effectively would dictate that no child is ever Tamei. Whenever a child comes in front of Beis Din, Beis Din must rule that he is Tahor based on the "Chezkas Tahor" combined with the Mi'ut. Since this is in direct opposition to the Rov (that most children are Metafchin and therefore are Tamei), such a Chazakah cannot apply. In contrast, the Chazakah that the dough is Tahor does not directly conflict with the Rov that most children are Metafchin. That Chazakah does not address children at all; it deals only with the dough. Therefore, it applies to help resolve the doubt about whether a child who was Tamei or Tahor touched the dough.