As I mentioned in an earlier post, R. J. David Bleich has an article in the most recent issue of Tradition about the copepods in NYC water. As usual, he covers the topic with unbelievable depth, thoroughness and accuracy. His conclusion is that he is not yet convinced that there is sufficient infestation to be a problem but that if there is, then one must filter the copepods out of the water. On his way to that conclusion, he covers many interesting topics. One is, surprisingly, that of the spontaneous generation of insects.
As is well known, the Talmud (Shabbos 107b) states that lice may be killed on Shabbos because there is no prohibition to kill animals that are the product of spontaneous generation. As is also well known, scientists in the seventeenth century proved that spontaneous generation does not occur. In note 31, R. Bleich writes: "For an informative survey of the issues surrounding kinim see R. Nosson Slifkin, Mysterious Creatures (Jerusalem, 2003), pp. 191-204."
To reconcile or explain this contradiction, R. Bleich (ke-darko ba-kodesh) reviews all of the proposed views:
1. "Some scholars have taken the position that scientific reports based upon the clinical observations of researchers are unreliable"
2. There may be exceptions to the finding that spontaneous generation does not occur.
3. Lice today are not the same species discussed in the Talmud.
4. The Sages erred.
5. Reproduction that is subvisual is treated by halakhah as if it occured spontaneously.
6. There are more reasons to this ruling than spontaneous generation, which might very well have been incorrect.
R. Bleich himself sides with view #5, but I submit that it is correct to infer from both the reference in note 31 and the inclusion of the view in the list, that R. Bleich does not consider R. Nosson Slifkin's position on this subject to be beyond the pale.
Let me also add that R. Bleich does NOT include the reasoning offered by the Frumteens moderator (here):
So when Chazal say that lice do not reproduce but rather spring from sweat and dirt, they mean that lice do not impart into their eggs the same life-force that animals do, that their eggs have a Nefesh HaDomem, or partially a Nefesh HaDomem, and Halachicly their status is not that of eggs.