For some reason the questioner continued in another thread, so I’m bringing it here:
Rabbi wrote here in the answer regarding making tea on the Sabbath that cooking is not a physical phenomenon but an everyday action. Could Rabbi expand on that? What does it mean that cooking is an everyday practical phenomenon? Usually, in everyday life, we would not refer to the extract that comes out of the tea leaves into the cup as “being cooked.” Usually cooking is when you intend it, and you get some benefit from it, etc. … no?

My answer:
What people call cooking is cooking. You do not need a chemical analysis of the process in order to determine whether there is a halakhic prohibition involved.
Let me give you an example. Once an avrekh asked me whether glass is a liquid or a solid. That avrekh had heard that among physicists glass is considered a liquid because it has a disordered crystal structure (solids have an ordered crystal structure—known as a Bravais lattice). I told him that if he meant it as a halakhic question, the answer is no. Physicists define the concepts on the scientific microscopic plane, but Jewish law deals with what we see. And what we see is that glass is a solid.
The same is true regarding cooking. When the Sages decided that making tea is cooking, this was not based on chemical or physical analysis but on an ordinary, everyday, common-sense way of looking at it. The extract that comes out of the tea leaves is definitely being cooked from that perspective. And even if you do not think so, the Sages did think so. Either way, scientific objections are not rele

On the same topic, Rabbi once wrote (and I myself act this way out of doubt) not to kill a louse on the Sabbath, even though I have never seen a louse produced from sweat, because the knowledge of the Sages was mistaken on this issue of how lice come into being. Rabbi Yitzhak Yosef wrote that despite the research of the “natural philosophers,” for us, regarding Jewish law, we have only the words of the Sages, according to whom the louse comes from sweat. Based on this, it may be that here too, the determination whether something is alive or born from parents like itself depends on the old common-sense appearance, in which creatures could come into being from the liquid in which they live (“Let the waters swarm with swarms of living creatures…”) and not from parents like themselves, and for such creatures there is no prohibition against killing them on the Sabbath because of slaughtering. It follows that we are forbidden to rely on knowledge obtained through a microscope, and only on unaided appearance and on the mode of thought (imaginations) current in the period of the Hebrew Bible (Tanakh) and the Sages, and all that remains for us is to classify things.

Lice were considered in Jewish law to be the filth of the body, perhaps because they are human parasites and have no independent existence without a human host. Maybe as a result they were not considered independent creatures whose killing is forbidden on the Sabbath (even though the Talmud and the halakhic decisors link this to self-reproduction).

Ailon, that is really not the same thing. There the Sages were scientifically mistaken. In the context of glass or cooking, this is not a mistake but looking at things at a different resolution. The science of the Sages does not bind us in any way.

Y.D., if you are already abandoning the Babylonian Talmud’s reason that they reproduce from sweat, and you still stick with the leniency but not for their reasons, then it is already better to adopt the Jerusalem Talmud’s reason, which explained that Beit Hillel permitted killing a louse on the Sabbath because it lives for a very short time (a fact that has remained scientifically true to this day).

I am not sure I am abandoning it (as I explained, they are parasites of the human species and therefore are not defined as an independent creature). But there is another implication of the fact that we do not accept the science of the Sages regarding the laws of hand-washing. If lice are not produced from human filth, it may be that one need not wash one’s hands after removing lice.

It could be there is no connection, and even if lice come from eggs they still bring on an evil spirit, as I argued in a post here:
https://wordpress.com/post/yuddaaled.wordpress.com/43
But perhaps just as, according to Rabbi Michi’s view, it is forbidden to kill lice on the Sabbath, so too one would not need to wash one’s hands after removing them. What does Rabbi think??

I think that washing the hands does not necessarily have to do with the assumption that lice are born from human filth. There is a sense of having dealt with something disgusting and dirty, and therefore one washes one’s hands. To nullify a Jewish law, a solid argument is required.

The Sha’arei Teshuvah on Orach Chayim, section 4, subsection 12, distinguishes between a flea, which is not produced from human sweat and for which one only needs to clean one’s hands, and a louse, which is produced from human sweat and for which one must wash one’s hands. If a louse is not produced from human sweat, then seemingly one would also not need to wash one’s hands.

The question is whether he is right. According to his approach, it is obvious that today this is no longer true and no longer binding.

It is not entirely correct to say that the Sages were mistaken. They were not scientific at all. They operated out of the ancient conception of reality, which relative to our science is considered “pre-scientific” (part mythology and part philosophy), and ordinarily we would call this conception of reality “fantasies.” But one can see these very fantasies as a view of reality at a very coarse resolution. In a certain sense, saying that the Sages were mistaken is like saying that Newton was mistaken. That is a bit simplistic. Newton is true within the limits of low velocities and weak gravitational fields (relativity), and at scales that are not too small (quantum theory). The reality he described is a garment for the Einsteinian or quantum reality. Here too, to some extent, the mythological/philosophical conception is something like the outermost garment of scientific reality. One can say that the Sages were mistaken only about things that count as a mistake at their own resolution, not based on claims from higher resolutions of truth. In the world of human beings in the time of the Sages, the idea that creatures can come into being from their environment without parents is an observational “fact.” From our point of view it is not “incorrect” but simply imagination (“not even wrong,” “undefined,” “primitive”), something that does not exist at all. In the current scientific biological paradigm, there is no such thing as a living creature that comes from something non-living, aside from the question of the origin of life.