(While Rabbi Meiselman does not remotely prove his assertion that any definitive statement of Chazal about the natural world is unassailable, we will not dwell upon that for now.)
Although Rabbi Meiselman concedes that tentative statements of the Sages could be in error, he insists that we ourselves are not allowed to draw this conclusion:
"The human mind - even that of a Tanna or Amora - has limitations... Sometimes even a great scholar may err... Nevertheless, the prerogative of declaring any of their teachings mistaken is granted to them, not to us. For anyone other than Chazal themselves, questioning their conclusions is called being melagleg al divrei Chachamim - "mocking of the words of the Sages" - a crime with very serious consequences." (p. 108)In this post, I will not deal with the difficulty of reconciling this with countless topics from the Gemara and sources from Rishonim and Acharonim that are not mentioned in Rabbi Meiselman's book. It is sufficient for now to discuss only the difficulty of reconciling this with other topics in Rabbi Meiselman's own book.
Let us first consider the case in Pesachim, where it is Rabbi Yehudah HaNasi that concedes that the gentiles are correct with regard to the sun's path at night. That would initially seem to fit well with Rabbi Meiselman's principle. But let us suppose that Rabbi Yehudah HaNasi would not have conceded to the gentiles (or let us suppose that that part of the Gemara would have been lost). According to Rabbi Meiselman, it would then have been forbidden for us to say that the sun goes on the other side of the world at night!
Rabbi Meiselman does not even seem to observe his own methodology with other cases that he discusses later in the book. For example, with regard to the mouse that is generated from dirt, Rabbi Meiselman says that Chazal were not definitively stating that it exists, only tentatively exploring the possibility. It is therefore, he says, not problematic to point out that there is no such creature. But Chazal never said that Chazal were wrong! Isn't he contravening his own methodology, quoted above? Is he not being melagleg al divrei Chachamim by his own definition?
Things get even more strange and problematic when we read more about Rabbi Meiselman's approach regarding cases where Chazal were speaking tentatively and were in error:
"...Whether Chazal were speaking definitively or tentatively, they were never - in the opinion of these authorities - merely presenting contemporary science (note - in a footnote, he says that practical medicine may be an exception). They were presenting insights about reality derived from the Torah... Consequently, even when a tentative statement of Chazal is in error, it is not an error in science but an error in the interpretation of the Torah." (pp. 107-8)This is remarkable! Remember how the Gedolim came crashing down upon me for saying that Chazal made errors in science, due to their following the scientists of their era? Isn't it much, much worse to say that Chazal were actually making errors in Torah rather than in science?!
Furthermore, how can this be reconciled with what Rabbi Meiselman writes elsewhere in the book? The most obvious example of Rabbi Meiselman's principle is the case in Pesachim. So, Rabbi Meiselman is telling us, the Sages who believed that the sun goes behind the sky at night were not following the contemporary Babylonian cosmology; instead, they were solely, albeit tentatively, deriving their position from the Torah. It is extremely difficult to reconcile this with what Rabbi Meiselman writes in the chapter about Pesachim, where he is arguing that the Sages of Israel were wrong precisely because they could not obtain their knowledge from the Torah (and to which I responded that elsewhere in the Gemara, we see that they did relate their cosmological view to Scriptural exegesis).
Those of us who follow the rationalist Rishonim and Acharonim, and who do not subscribe to Rabbi Meiselman's assertion that only Chazal can point to errors in Chazal's statements, will observe a remarkable phenomenon. There are numerous cases where Chazal's statements about the natural world are incorrect, whether they are referring to salamanders spontaneously generating from fire, seven-month fetuses being more viable than eight-month fetuses, the kidneys providing counsel, hyenas changing gender, etc. According to Rabbi Meiselman, we are not allowed to declare any of these to be mistaken; and even if they were mistaken, they were mistakes in the Sages' interpretation of Torah - they were not presentations of the mistaken science of their era and had no connection to it. But where does the Torah speak about salamanders coming from fire or hyenas changing gender? And isn't it an extraordinary coincidence that those insights which turn out to be in error are so often identical to the errors made by non-Jewish scientists of that era?