Avodah Zarah

Why were the three clauses  which are taught necessary? — It is quite right that he quotes the third because he thereby teaches us that there is difference of opinion even when it deteriorated from the outset. The second likewise [taught us that] if it improved and in the end deteriorated all agree that it is prohibited. But why [quote] the first clause? Since in the third clause, where no improvement at all occurred, the Rabbis prohibit it, how much more so [must they prohibit it] where there was improvement! — Abaye said: The first clause is necessary because of R. Simeon,  and the Rabbis spoke thus to R. Simeon: This dough should take two hours to leaven and what caused it to leaven in one hour? — [Yeast which was] prohibited.  How does R. Simeon [meet this argument]? — When there was improvement it was caused by both [kinds of yeast]  and when there was deterioration it was also caused by both. But according to R. Simeon, the lawful and prohibited elements should be combined and render [the dough] prohibited! — R. Simeon follows his own opinion, viz., that even two prohibited elements  are not to be combined,  for we have learnt: 'Orlah and mixed plantings may be combined; R. Simeon says that they may not be combined. A mouse fell into a cask of beer and Rab prohibited the beer. Some Rabbis mentioned this in the presence of R. Shesheth and remarked: He evidently was of the opinion that when it imparts a worsened flavour it is prohibited. [R. Shesheth] said to them: Rab certainly maintains elsewhere that when it imparts a worsened flavour it is permitted. Here, however, we have an anomaly since it is something repugnant and people recoil from it; and even then the Divine Law prohibited it  with the consequence that although it imparts a worsened flavour it is nevertheless prohibited. The Rabbis said to R. Shesheth: According to your argument [a creeping thing] should defile  whether moist or dry; why then have we learnt: They defile when moist but not when dry!  — And according to your reasoning semen should defile whether moist or dry; why then have we learnt: It defiles when moist but not when dry! What, however, you could say is that the semen of which the Divine Law speaks [as defiling] is such as is capable of causing fertilisation; and likewise here [in connection with creeping things] the Divine Law uses the expression when they are dead,  i.e., when they have the appearance of being dead.  R. Shimi of Nehardea objected: Is [the mouse something] repugnant; is it not brought upon the table of kings! — R. Shimi of Nehardea said:  There is no contradiction, for [what is served at meals] is the fieldmouse and [what fell into the beer] was the domestic mouse. Raba said: The legal decision is that when it imparts a worsened flavour it is permitted, but what was Rab's reason [for prohibiting it] in the case where a mouse fell into beer I do not know. Was it because he held that when it imparts a worsened flavour it is prohibited and the legal decision is not in agreement with him, or because he held that when it imparts a worsened flavour it is permitted but a mouse in the beer causes an improvement [to the flavour]! The question was asked: