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Tuesday, July 05, 2005

Is נשתנה הטבע a viable answer for conflicts between Torah and science?

Many of those who hold that Chazal never made mistakes in science, rather their science is part of Torah shebaal peh and was received at Har Sinai, explain seeming conflicts between torah and science by saying נשתנה הטבע, nature changed. IMHO, this is an untenable position for the following reasons.

1. They hold that all of Chazal's science is part of Torah. This means that when Chazal said that remedy x cures sickness y, that was part of Torah, it was received at Har Sinai. Why doesn't it work today? The world changed. This makes no sense. Torah preceded the world by 2000 years (Gemara Shabbos). Hashem created the world by looking into the Torah. How can you say that things in the Torah are no longer true? For over 4000 years remedy X cured Y, suddenly after the era of Torah Shebaal Peh ended the world changed so this stopped working and the torah became untrue, why would Hashem do such a thing? It makes Torah into a joke. Why would Hashem change the world so that Torah no longer reflects the world if the world was created based on Torah.

Even more then that, this seems to contradict the Rambam's principle of the immutability of Torah. Torah has now changed. It used to be that the Torah provided a rememdy for sickness Y, now it no longer does. It used to be that the Torah explained various natural phenomena, now it doesn't. In other words the Torah changed because it no longer reflects the physical world.

2. If Chazal had a kabbala (tradition) about science you would think that they would have had a kabbala that the world is going to change and that the science would no longer be true. נשתנה הטבע should also be part of Torah. After all, if you are going to claim that all of science is in Torah then this very important fact should be there as well. Yet, Chazal never even hint that the scientific pronouncements that they are making are only temporary. They didn't say that remedy X will only work for a limited time. they made a blanket statement that remedy X cures Y. It is clear that Chazal had no idea that נשתנה הטבע was going to happen, why not? If Torah included science it should have included נשתנה הטבע as well.

3. There is not a shred of evidence that נשתנה הטבע. Remember, the Geonim who lived only a few hundred years after the time of the gemara already stated that the cures of Chazal don't work, that is a very short time. Here are some examples of things where it is quite implausible to say that נשתנה הטבע.
a. The Gemara in Bava Basra (25a) states clearly that Chazal held that the Sun revolves around the Earth and that the Earth is surrounded by a roof that the sun goes out of at night (see Chazal and Mistakes in Science for more about this). It would be preposterous to claim that in the times of Chazal the Sun revolved around the Earth and went out a window but now נשתנה הטבע and the Earth revolves around the sun etc. Everyone can understand that such a change didn't happen.
b. The gemara seems to say that lice are born from spontaneous generation. again it is not plausible to think that in the times of Chazal there was spontaneous generation but in the last 1500 years it stopped
c. The gemara states that the mother contributes the blood to the baby (based on this some poskim didn't want to accept blood tests to establish paternity). It is implausible to think that the whole nature of human development changed after the time of chazal.
In fact, I don't see a single torah science conflict where it is plausible to say נשתנה הטבע.

Based on the above, it is clear that נשתנה הטבע does not answer any contradictions, rather it is a copout, meaning that we have no answer. The real answer would seem to be like those Rishonim and Acharonim who hold that Chazal did not have a kabbala on science and therefore could make mistakes in science.

I found a fascinating site השתנות הטבעים which has a long list of things where what Chazal say doesn't fit the scientific facts of today. If you look at the list (which is only partial) you will see that it is quite large. To believe that in all of these things נשתנה הטבע is quite a stretch for anyone. Here are just some of the changes related to the human body. You would have to believe that the human body changed drastically as
a. none of the remedies of chazal work
b. the things that Chazal say are dangerous are not (e.g. eating or cooking fish and meat together), and things tht Chazal say are good for you (rotting fish) are dangerous
c. Genetics changed (it was once a good thing to marry your niece)
d. all things about birth and a baby's development changed (see 7, 8 , or 9 month pregnancies), the position of babies when born, women don't get pregnant from the first sex act, etc.
e. all things related to hilcho nidda changed - until when a woman can give birth (60 if she gets married before 20), when does a women stop menstruating when pregnant, how long does a woman not menstruate after birth, the whole idea of וסתות and הרגשה
f. various halachos related to mila such as washing the baby on the third day, metzitza bpeh (which was considered to be necessary to ensure the safety of the baby).
g. the din of פצוע דכא
h. various foods/actions that are קשה לשכחה

To say נשתנה הטבע on one of these maybe, on all of these (and this is just a drop in the bucket) is clearly ridiculous, there is absolutely no evidence that from the time of Chazal until the time of the Geonim/Rishonim, who pointed out many of these, (which is a few hundred years), or even modern times, there were wholescale changes in humanity such that all of these changes could have taken place.

Update 2
R' Feldman writes As the Leshem cited above says, if even regarding matters which are not related to halacha, the Sages say, sod Hashem liyerav, “G-d reveals the secrets of nature to those who fear him,” then certainly there must have been siyata dishmaya (Divine assistance) and even ruach hakodesh (a Divine spirit) assisting the Sages in their redaction of the Oral Law. It is therefore inconceivable, to these opinions, that G-d would have permitted falsities to have been transmitted as Torah She-be-al-peh and not have revealed His secrets to those who fear Him.

My response to this is that according to him it comes out Hashem transmitted information as Torah Shebaal Peh that then became untrue because Hashem changed nature. Is that any more conceivable? Is it any more conceivable that Hashem would reveal scientific facts in Torah and then change nature to invalidate that revealed Torah without telling Chazal (after all Chazal in their scientific pronouncements never even hint that things will change)?

In other words his argument falls apart because even according to him hashem did not reveal everything to chazal because bottom line, we have a gemara full of remedies that don't work. Using his logic, how could it be that hashem didn't reveal the secret that nature was going to change? How could he have allowed Chazal to put remedies and other scientific facts in the gemara that were going to change?


At 10:48 AM, Anonymous Anonymous said...

"3. There is not a shred of evidence that נשתנה הטבע. "

this is not true! For ex, people who should know such things tell me that the position of organs in animals is not the same as described in gemara. So chazal shecht animals, and organ layout looks one way, we shecht them and they look different. It must be that nishtane hateva (and some of this is fairly radical change).

I think what is true is that nishtane hateva is so ridiculously overused as an explanation that people start to think it is always a euphemism, when some amount of nishtane hateva clearly occured.

Also, some (esp relating to when women get periods etc) is most likely diet related etc.

At 11:00 AM, Blogger bluke said...

I find it hard to believe that the postions of the organs changed. I don;t see any real evidence. It is much more plausible to say that chazal were talking about different animals or different organs or we are muisunderstanding chazal. Remeber Chazal are describing things in words not pictures, using terms that they understood. Is there any source outside of Chazal for such a change? After all, if the layout of the internal organs of animals changed you would think some in the non-Jewish world would have noticed as well.

At 11:14 AM, Blogger bluke said...

Don't get me wrong I have great respect for Chazal. However, when you want to make a statement of נשתנה הטבע it would have affected the whole world. If there is no evidence from the rest of the world it calls the whole concept into doubt.

In addition, you didn't address my first point. namely, that if you hold science is Torah and נשתנה הטבע then Torah is changing and becomes untrue.

To say נשתנה הטבע if you hold that Chazal used the science of their times is much more plausible, we don't run into a situation where a part of Torah suddenly becomes untrue. Of course then you don't really need נשתנה הטבע but it would work in cases where Chazal made direct observations of the world that are contradicted by science today.

I have to say that I am very skeptical of נשתנה הטבע. As I said there is no evidence from any outside sources that such a thing ever happened on the scale that is needed to answer these questions.

At 11:18 AM, Blogger bluke said...

Anonymous, please bring some sources backing up your claims. I will bet that the gemara's that these are based on are the subject of a machlokes harishonim how to understand it and very possibly a machlokes acharonim. Besides as I stated, words are a very poor vehicle for explaining how the inside of an animal looks, in this case a picture is truly worth a thousand words.

At 12:18 PM, Anonymous Anonymous said...

I heard R Bleich say this multiple times, and posit that this is strong support for evolution *within* species.

I tend to doubt that he's confusing which animals are which or misunderstanding what's being described or not noticing a machlokes rishonim - he tends to be reliable on things like this - but your question about why no one else noticed is good, and if I have opportunity I'll ask about that.

I didn't address the rest because I don't think nishtane hateva is any kind of across the board explanation - I think it's an explanation for isolated instances that has been stretched far beyond it's capacity to explain. I was just saying that it seems to be the most reasonable explanation for *some* incidents.

At 12:22 PM, Anonymous Anonymous said...

I don't think there is ONE answer to science/torah conflicts. Some things they may have learned from droshos and/or had some kabala on (maybe they only had kabala on isolated things, or didn't preserve scientific information with the same diligence that they preserved halacha). On other things, they probably took from the science of their day and erred. Sometimes maybe they were talking allegorically or nishtane hateva - eg some cures, if we knew what they meant and what doses etc maybe they work, although perhaps not as well as modern cures. (Even that doesn't mean that it's misinai - after all, why would the cures chazal relied on be any worse than eg african folk cures, some of which turn out to have some substance?) I don't think any single blanket solution covers all cases - some explanations make more sense than others for specific instances.

At 12:24 PM, Anonymous Anonymous said...

"but your question about why no one else noticed is good, and if I have opportunity I'll ask about that."

I don't know who else had written records about such matters at the time, though.

At 12:35 PM, Blogger bluke said...

The gemara was compiled bewteen approximately the years 200-500 CE. In other words, until 500 CE nothing had changed (otherwise it would have been noted or removed from the gemara). The Geonim discovered discrepancies 200-300 years later, the Rishonim a 500-800 years later. There are plenty of written records from the year 500 CE and onwards. None of them to the best of my knowledge make any reference to any kind of changes in animal biology, human biology etc.

At 12:40 PM, Anonymous Anonymous said...

Yes, I understand, but was anyone else at the time keeping detailed records of what the internal organs of animals looked like as we find in chulin?
I don't think the geonim remark on this particular change.
I think you're lumping all science/torah conflicts together - I'm talking about one specific change, that chazal shecht animals and say it looks like this, and today it is not like that.
I'm not talking about all incidents - just ones where they describe a particular metzius. This has nothing to do with broader science/torah conflicts.

Some changes are definite - eg when they describe when and how women get their periods - and they are unremarkable, as these things change relatively quickly due to environmental factors. It is not *always* crazy to say nishtane hateva - sometimes it's the reasonable explanation, that was my only point.

At 12:43 PM, Blogger bluke said...

Anonymous wrote On other things, they probably took from the science of their day and erred.

According to R' Feldman, R' Elyashiv and others you are not allowed to say that.

Here is a quote from R' Feldman's letter
Why does mainstream opinion reject R.Avraham’s opinion? This is not because they considered the Sages greater scientists than their modern counterparts. Rather, they believed that, unlike R. Avraham’s view, the source of all the knowledge of the Sages is either from Sinaitic tradition (received at the Giving of the Torah) or from Divine inspiration.
R. Yosef Shalom Eliashiv, a signatory to the ban, was asked: if he considers Slifkin’s approach wrong how could so many earlier authorities have held it? He answered: “They were permitted to hold this opinion; we are not.”1 In other words, they were authorities in their own right qualified to decide matters of Jewish law. We are not permitted to do so.2 We are enjoined to follow the majority opinion and our tradition as to how we are to approach Torah.

At 12:48 PM, Blogger bluke said...

I agree with you that sometimes it is reasonable, menstruation is one of those (in fact, we see changes happening before our eyes). However, even here there is a problem. If every statement that Chazal made was torah, then נשתנה הטבע is changing torah and making it untrue.

In any case, this approach is used to answer many more conflicts then what you proposed.

If you hold that Chazal used science of their day, then in a limited fashion I can understand saying נשתנה הטבע in the few cases where it makes sense. But to explain away all of Chazal's cures or much of the list that I posted from that website is a non-starter.

At 1:00 PM, Anonymous Anonymous said...

Yeah, and what will they do with the ramban on chumash who also says that chazal erred on science? He is more reluctant to use this explanation than other rishonim, but he does use it. They are acting as though this is some extreme view espoused by the philosophically oriented rishonim, some gaonim, those like RSRH...but actually, if there is a single rishon whom the charedi world is closest to ideologically it's the ramban. (It's not accidental that REEDessler bases so much of his thought on ramban.) How are they going to relegate the ramban to minority? It's one thing to say the rambam is idiosyncratic hashkafically and "we" don't follow him, but have you ever heard anyone suggest that there are radical hashkafas in ramban on chumash that aren't accepted? the ramban on chumash espousing ideas that were ok for him, but klal yisroel has ruled out --- and no one noticed this, ever, until this ban was signed? Please.

At 1:24 PM, Anonymous Anonymous said...

"If you hold that Chazal used science of their day, then in a limited fashion I can understand saying נשתנה הטבע in the few cases where it makes sense. "

actually, these are mostly cases where they are not really using "science" so much as describing the metzius they saw.

By contrast, d on your list is mostly a theory of pregnancy. That's the one on your list that is the most problematic.
I think your list is a good demonstration of the fact that there isn't one answer that works equally well for all instances - different explanations work better for some of those than for others.

At 2:01 PM, Blogger bluke said...


Can you post a reference(s) to where the Ramban on chumash states that chazal made mistakes in science. I would really like to look it up and see them inside.

At 2:52 PM, Blogger Rebeljew said...

Nishtana HaTeva is pure sophistry, nothing more. Anon, until you can establish that facts were ever as the Chachamim said, nishtana hateva is nothing more than an "escape from between the horns" argument.

Of course, Chachamim in the Gemora are not writers of a science textbook. They rule on Jewish law regarding science facts, not on science itself. That is their only mandate (lo sasur, al pi hatorah asher yorucha, only applies to judging, not to anything else), to make judicial rulings, not factual ones. They are the judge, lav davka, the jury. The eyewitnesses do that job. Note that the eyewitnesses do not have be lamdanim, just trustworthy and impartial.

Good work, Worker.

At 3:20 PM, Blogger Rebeljew said...


It says clearly in Mesichta nida, as brought down by the Ramban at the beginning of Tazria, for instance:

a) the female seed is coagulated blood (This changed to be the human ovum in 1827?)
b) the red / dark parts of the body come from that seed, including the black of the eye (This changed to a whole DNA based system, and the solid pupil turned into a hole sometime later. Also, historically evidence of DNA was retrofit into evidence that we have found.)
c) The white parts of the body are formed from the male seed (again the whole DNA system was retrofit).

Though this secret mystical knowledge was secret from Jews, even the most learned Rabanim, it was well known to non-Jewish scientists of the time. Sod Hashem liYerayav?

At 5:24 PM, Anonymous imainish said...

Where and when was R' Feldman letter printed? Is it online in it's entirety?

At 5:36 PM, Blogger bluke said...

The letter is online in it's entirety here

At 2:23 AM, Anonymous Anonymous said...

for the ramban:

in vayikra 12:2 he gives equal weight to the scientific view that contradicts chazal

see also breishis 9: 12

At 2:28 AM, Anonymous Anonymous said...

Rebel : I wrote I think pretty clearly that I think nishtane hateva is used sophistically to explain things it can't explain. I don't know why you are writing this therefore:

"a) the female seed is coagulated blood (This changed to be the human ovum in 1827?)
b) the red / dark parts of the body come from that seed, including the black of the eye (This changed to a whole DNA based system, and the solid pupil turned into a hole sometime later. Also, historically evidence of DNA was retrofit into evidence that we have found.)
c) The white parts of the body are formed from the male seed (again the whole DNA system was retrofit)."

esp since I distinguished explicitly between things that chazal observed and described and their scientific theories of pregnancy.

My point was not that nishtane hateva is some kind of all purpose explanation for science/torah conflicts but just that it happens. Most trivially, it happens for many things relating to menstrual cycles - in (most of us older folk anyway) own lifetimes we see changes from one generation to the next due to diet. It also appears to have happened for some other things that chazal described. They were regularly cutting up animals for karbonos, they knew what they looked like. SOME things are different. These are not for the most part things people mean when they refer to "Science/torah conflicts"

At 4:07 AM, Anonymous Anonymous said...

also see the ramban shmos 12: 42,where he clearly entertains that chazals drosho of minyan r'du is not b'mesora and can be rejected - he offers a different count and then says *if* minyan r'du is a mesora, then maybe we can accomodate the view. This is a somewhat different issue than whether they erred on science, but if the rationale for thinking chazal never erred on science is sod hashem l'yireyov, and it's "inconceivable" that there are any errors in tsb"p, then why would the ramban be entertaining that they erred in history?

At 4:15 AM, Anonymous Anonymous said...

My theory is this.
People barely notice the ramban challenging chazal, because his *tone* is very palatable to charedim. He is reluctant to reinterpret based on science ("al korcheynu"), he quickly says I'm disagreeing with chazal, but if it's a mesora, then of course we can understand as follows, etc.
This is a very different *tone* than the rambam's sweeping "don't ask me questions about chazal's medical information b/c they weren't scientists" or RSRH's blanket approach.
The charedim IMO are just uncomfortable with the instinctive rejection of anything chazal said - the charedi world is comfortable with the approach that looks for grounds on which to justify what chazal said on whatever topic.
But if we are dealing with kefira, then following the ramban's approach is kefira too.

I would have said that the ramban's approach - that they could have erred, but not a sweeping rejection of all they said as per the rambam = was a very mainstream approach in charedi circles before this ban began.
I think the banners just boxed themselves in by defending the "kefira" charge when really they just don't like Slifkin's *attitude* or tone.

At 7:49 AM, Anonymous Anonymous said...

In regard to mrdical cures,I have heard the Nodah Beyehuda quoted as saying that it is prohibited to use them now. The reason being the change in climate from their time to ours. Also the fact we are not certain of all the correct translations of the items that they mentioned. And even when we know the correct translation; the wheat (as an example) is adifferent form of wheat in our times, than the wheat that they had.

At 10:12 AM, Anonymous Anonymous said...

the problem is not really explaining cures, it's explaining (just for example) their theory of how the fetus develops, their model of pregnancy etc.

At 8:30 AM, Anonymous kaspit said...

Greetings. You might be interested in my post about Artscroll on Talmudic medicine. It also links to here. Take care,


At 5:31 AM, Anonymous Tal Benschar said...

I know this is nearly a year after the fact, and perhaps no one will notice this post, BUT

There is one example where nishtaneh ha teva is without a doubt the case.

Chazal say (and it is brought down even in Shulkhan Arukh) that most women have a veses kavuah -- meaning they mensturate with regularity either at the same time of the month or at the same interval between menstruations.

This simply MUST have been the case in the time of Chazal (and probably later), because (a) it was readily observable by women keeping track of the days; (b) women were REQUIRED to keep track of their veses to know on what day to separate from their husbands; and (c) every woman has a different veses, so it was not simply a dictum thrown around without checking.

Yet ask any Rov today, and he will tell you that it is very rare for a woman nowadays to have a veses kavuah -- i.e, that a woman will menstruate three times in a row on the same day of the month or at the same interval.

Of course, this is probably a far less radical change than is sometimes contemplated when "nishtaneh ha teva" is invoked.

At 5:08 AM, Anonymous Anonymous said...

There are several problems with claiming that nature changes. One is in halacha: how do we ever know we are dealing with the same metziut as chazal when we deal with a shaila depending on natural fact? Even if we have a mesorah that, say, a certain defect in a cow does or does not make it a a treifah, how do we know that the nature of cows didn't change today, or worse how do we know it won't change tomorrow since a treifa is a prediction of the future, to make the defect more or less dangerous to the cow?

There are also conceptual problems. In the first place, scientist have looked very hard for changes with time in fundamental physical constants, and have failed to find them. In some cases the bounds are very tight. Some how Hashem changed all this biology, without changing any physics. And for what reason? To confuse students of gemorra?

Chazal tell us that Hashem "histakel b'oraita u'varah olmah" God looked at the Torah and created the world. Since the Torah is immutable, one would think that the basic structure of the world was, too. Likewise, the list in Pirkei Avot of "specialty items" created at the very end of creation would seem to imply that Hashem doesn't change the nature of his creation readily.


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