Commentary for Avodah Zarah 97:11

The Talmud raises a difficulty from a source about orlah, fruit that grows during its first three years. One may not use such fruit. According to R. Yose, one can use the young shoot to plant a new tree, but one may not plant the nut, because the nut is fruit. However, ex post facto, R. Yose agrees that if one plants a nut, the fruit that grows eventually from the tree may be used. This is because the tree that grows is a case of “this one and that one causes.” The tree grows from the nut, but the nutrients of the ground and water also cause to the tree to grow. Thus it seems that R. Yose is lenient in such cases.

This is an attempt at a resolution of the contradiction between the two statements of R. Yose. It could be that R. Yose is stringent in cases of idolatry. He would hold that in cases involving idolatry when there are two causes, the product is still prohibited (i.e. the case of the mishnah with the falling leaves) but lenient in other cases (the case of orlah). The problem is that the Talmud cites another case involving idolatry. These cases are also “this and that are causes.” The manure fertilizes the field, but so does the dirt that is already there. The vetch fattens the cow, but so does other food. And yet the Talmud suggests the R. Yose is the lenient baraita because even in cases of idolatry he holds that two causes are permitted.

The Talmud rejects the identification of the baraitot and suggests that instead of a dispute between R. Yose and the rabbis, we have here a dispute between R. Eliezer and the rabbis. This means that R. Yose can be stringent in the case of idolatry (the mishnah) but lenient in other cases (orlah).
The following section will attempt to identify which dispute between the rabbis and R. Eliezer is also about cases in which there are two causes.

Eliezer and the rabbis disagree over a case where two pieces of leaven (starter dough) fall into a batch of dough and cause the dough to rise (neither was sufficient in and of itself). One of these pieces is terumah and can be eaten only by priests, and one is non-sacred and can be eaten by anyone. According to R. Eliezer, the status of the dough follows whatever the last piece of leaven was, because this is the leaven that causes fermentation. Abaye adds that if the forbidden leaven was left in there, then in all cases the dough is prohibited. Thus R. Eliezer seems to hold that in cases with two causes, one permitted and one prohibited, the result is prohibited. The rabbis would be lenient. This seems to locate the dispute between the two baraitot in yesterday’s section.

The problem with the above suggestion is that it depends on Abaye’s explanation of R. Eliezer. Abaye is the one who implied that in cases of two causes R. Eliezer prohibits. Abaye’s explanation allows us to pair R. Eliezer and the sages dispute with the two baraitot concerning the field fertilized with idolatry or cow fed with idolatry. But the simple reading of R. Eliezer is that the ruling depends on which substance is put in last. If the permitted leaven was put in last, R. Eliezer may permit the dough even though the forbidden dough was still present. In other words, R. Eliezer may not hold that in all cases of two causes the result is prohibited. He may hold that the principle is that we simply follow whatever was put in last.

Eliezer refers to a situation in which bread was baked in an oven heated up with wood from an asherah tree. This is another case of “this and that cause” for the prohibited wood and the permitted oven were used to cook the bread. Thus R. Eliezer is the strict opinion—in cases where there are two causes, one prohibited and one permitted, the rule is stringent.

We have identified R. Eliezer as representing the view that when there are two causes, the product is prohibited. But who are the rabbis who disagree with him. It can’t be the rabbis in that very mishnah, because they rule even more strictly.

The second possibility is that it refers to the rabbis in the mishnah about the two leavening agents, one prohibited and one permitted. They hold that no matter what order they are put into the dough, the dough is permitted. But just because they are lenient when it comes to terumah dough does not mean that they are lenient even with regard to idolatry.

The Talmud resolves the matter by saying that R. Yose does hold that when there are two causes the product is permitted, as we saw in the case of planting a nut of orlah—it is permitted to use what grows because there were two causes, nut and ground. So why then does he say that it is problematic to plant under an asherah tree because the leaves will fertilize the plant? This, the Talmud answers, was not his own opinion. He was only responding to the rabbis—you rabbis who hold that when there are two causes the product is prohibited should hold that planting under an asherah should be prohibited even in the winter.
And the rabbis would say it is permitted because while there is a gain in fertilization, there is also a loss because the shade prevents them from getting sun.

It is forbidden to plant under an asherah tree, even in the winter.

The produce in this garden is prohibited in accordance with R. Yose.