Sunday, April 30, 2006

Sources Indicating That Chazal Did Not Possess Perfect Scientific Knowledge

Revised November 16, 2010

Comments and update details at the bottom of the Table of Contents post.

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Table of Contents

I. Introduction

I-A. Overview
I-B. Purpose of This Compilation
I-C. Some Preliminary Observations
I-D. Technical Remarks
I-E. Acknowledgements

II. Sources from the Talmudic Era

II-A. Babylonian Talmud
II-B. Other Sources

III. Post-Talmudic Sources

III-A. Not All Scientific Assertions in the Talmud Are Necessarily Correct Even If Uncontested in the Talmud

III-A-1. Explicit
III-A-2. Indicative
III-A-3. Suggestive

III-B. Not All of the Talmudic Sages' Scientific Beliefs Were Necessarily Correct

III-B-1. Explicit
III-B-2. Indicative
III-B-3. Suggestive

III-C. Chazal Relied on the Scientific Knowledge, Research and Scientists of Their Times

III-C-1. Explicit
III-C-2. Indicative
III-C-3. Suggestive

III-D. Chazal Were Not Scientifically Omniscient

III-D-1. Explicit
III-D-2. Indicative


I. Introduction


I-A. The bulk of this article consists of quotations from post-Talmudic sources indicating that the scientific knowledge of the Talmudic sages (henceforth, Chazal) was less than perfect. These sources are divided into four principal classes:

Class A sources indicate that scientific assertions found in the Talmud may be incorrect, even if they are uncontested in the Talmud.

Class B sources indicate that not every scientific belief of every Talmudic sage was necessarily correct. These sources may not specify that errors are possible in uncontested scientific assertions found (specifically) in the Talmud. Since Class A is just an "extreme" subset of Class B (any source belonging to Class A belongs to Class B as well; see below), I have "double-listed" Class A sources in Class B as well, so that Class B does not appear deceptively small.

Class C sources indicate that Chazal relied on the scientific knowledge, research and scientists of their times. These sources do not directly discuss whether Chazal's scientific beliefs were always correct.

Class D sources merely suggest that Chazal were not all-knowing in matters of science – though I do not believe that this assertion requires sources to justify it at all.

Unless I am mistaken, each class is a subset of the subsequent ones. That is, the sources in Class A also qualify for Classes B, C and D; those in Class B qualify for C and D; and those in Class C could correctly be classed in D. I reason as follows:

Each scientific assertion advocated in the Talmud reflects the scientific belief of at least one Talmudic sage. Therefore, if, as per Class A, scientific assertions found in the Talmud may be incorrect, it follows that at least some Talmudic sage may have held an incorrect scientific belief; this is the defining thesis of Class B.

If (one or) some of the Talmudic sages' scientific beliefs might have been incorrect, as per Class B, then where did their incorrect beliefs come from? Not, surely, from a divine source – God would not make a scientific error. The source must have been a fallible, human one. This having been established, I think it eminently reasonable to posit that their beliefs – at least the wrong ones – came from the science and scientists of their era (possibly as a heritage from previous eras); this is the defining thesis of Class C.

Finally, if Chazal were relying on the science and scientists of their era, as per Class C, then they could not have been scientifically omniscient unless either (a) their scientists were scientifically omniscient, or (b) the entire massive corpus of scientific knowledge came to them divinely, except for certain pieces of information which scientists had to fill in for them. Neither (a) nor (b) is plausible, and thus we conclude that Chazal were not scientifically omniscient, as per Class D.

Within each class, sources are divided into three groups:

Group 1 sources are explicit. (What they are explicit about depends, of course, on the class to which they belong.) I have tried to be fairly conservative in what I judge "explicit."

Group 2 sources are what I have called "indicative." An indicative source seems impossible to explain reasonably unless one supposes that its author accepted the thesis under which it is classified. It is not, however, explicit.

A Group 3 source is one whose most probable meaning (in my opinion, of course) implies the particular viewpoint I have linked it with. It could also be assigned a different, yet still reasonable – albeit less likely – interpretation, according to which its implication would be different.

In cases where I have quoted multiple passages from one individual, I have classed that individual in the first section to which he can be assigned (i.e., A before B, B before C; 1 before 2, 2 before 3; etc.), and all quotations of him appear together in that spot. I have indicated which quotations are out of place as a result, and to which class and group they properly belong.

Sources bounded by question marks are ones I have not yet been able to gain access to; I have read about them in secondary sources only.

The Talmud and other classical rabbinic sources record scores of disputes between Talmudic-era rabbis concerning what are, at least on the surface, questions of scientific fact. These records would seem to constitute strong evidence in favour of (B) (and hence (C) and (D) as well). Numerous other passages in the Talmud and contemporaneous writings record instances in which a Talmudic rabbi consulted with doctors or other scientific experts regarding matters of scientific fact or opinion. These passages would seem, in turn, to constitute strong evidence in favour of (C), as well as being indicative of (B). I have listed some of these Talmudic-era sources in Section II.

I discovered much of this information with the help of secondary sources, including Rabbi Natan Slifkin's book Mysterious Creatures (Jerusalem: Targum, 2003) and his website,; Rabbi Gil Student's website,; the Open Access Project ( at Yashar Books' website; Torah and Science, by Judah Landa (Hoboken, NJ: Ktav, 1991); and two fine books by Rabbi Dr. Yehudah Levi: Facing Current Challenges (Jerusalem: Hemed, 1998; especially Chap. 33 with accompanying endnotes), and The Science in Torah (Jerusalem: Feldheim, 2004). Please understand that this list began as mere personal notes and has evolved only somewhat beyond that stage of development, so it may strike you as cryptic, unhelpful, incomplete, poorly written, badly edited, inconsistent in style, or in other ways flawed. One flaw I hope you will not find is factual error. If you believe that any of this information is misinterpreted or wrong, please say so in the comments. Also, if you have any sources or other information to add to this list, I would be delighted if you would be kind enough to share your knowledge in the comments too. I will update this post periodically with additions and corrections.

Purpose of This Compilation

I-B. I have been compiling this list because recently certain eminent Torah authorities, and many lesser figures following in their wake, seem to have questioned or denied the legitimacy of the belief, most famously advocated by Rabbeinu Avraham ben Harambam, that the Talmudic sages possessed flawed scientific knowledge. This type of viewpoint is presented in numerous works, such as the essay by Rabbi Aharon Feldman, Rosh Yeshiva of Ner Israel Rabbinical College of Baltimore, entitled "The Slifkin Affair – Issues and Perspectives" (available at, which is partially based on a discussion Rabbi Feldman had with Rabbi Yosef Shalom Elyashiv.

A similar point of view is presented in the first section – entitled "Likut Kedushat Hatorah" – of the book Afikei Mayim, by Rabbi Reuven Mordechai Schmeltzer (Monsey, NY, 2006), which bears the approbation of Rabbi Moshe Shapiro; and Rabbi Schmeltzer's Chaim Be'emunatam (Monsey, 2009), which I have not seen, but which I am told bears the approbations of Rabbi Shapiro, Rabbi Malkiel Kotler of Beth Medrash Govoha in Lakewood, New Jersey, Rabbi Elya Ber Wachtfogel of the Yeshiva of South Fallsburg (New York), and others. Note that the former work, which I have studied, reflects poor scholarship and is an inaccurate source of information. I have it on good authority that the latter book is even more dramatically unreliable. See Rabbi Gil Student's seven posts on Afikei Mayim, linked to at; and Rabbi Natan Slifkin's critique of Chaim Be'emunatam, available at

I have been taught, and continue to believe, that Rabbeinu Avraham's position is legitimate, first and foremost because it is almost certainly true. This list helps me to clarify to myself, and, especially, to explain to others, why I believe it to be true.

Some Preliminary Observations

I-C. 1. It would seem that an investigation into the source(s) and quality of Chazal's scientific knowledge ought to be primarily historical, as opposed to halachic. Any particular sage either held a certain belief (belief in spontaneous generation, for example), or did not. He either derived all of his scientific knowledge from the Written Torah and oral tradition, or he employed other sources as well. The truth of the matter is not subject to moral or halachic arguments. It happened in a particular way; which way that was is a question of historical fact. We should attempt to resolve that question – if we wish to do so truthfully – not via the usual method of halachic ruling, but by examining the relevant historical evidence, assigning each piece its appropriate weight. Therefore, by way of example, it would seem appropriate in this matter to assign greater weight to the opinions of the Geonim – who lived closer both in time and in location to Chazal – than we would in a typical halachic debate, where they might be more easily trumped by later, European authorities such as Rashba, Rivash or Rema.

2. I have limited this investigation, somewhat arbitrarily, to the question of Chazal's scientific knowledge. I see no reason, however, to assume that the quality of their scientific knowledge was different from the quality of, for example, their historical knowledge. Thus if we conclude that they relied on the science of their times, with its flaws, for their scientific knowledge, we may then be justified in supposing that they relied on the historical beliefs of their times – accurate or inaccurate, complete or incomplete, as they may have been – for their historical knowledge. This conclusion, if warranted, may be instructive in resolving contradictions between certain historical assertions of the Talmud and the findings of modern archaeology, such as the dating of the construction of the Second Temple.

3. Occasionally a post-Talmudic authority appears, in different passages, to adopt conflicting approaches to the authority of Chazal's science. I believe that one must evaluate each of these apparent contradictions on a case-by-case basis. Sometimes it may prove that there is not really any contradiction. In other cases, the author may have changed his mind. It is also possible that he wrote different things for different audiences or in response to different circumstances; this is not unknown in rabbinic literature.

One general rule of which I am reasonably confident is that a genuine Torah scholar is far more likely to exaggerate Chazal's strengths than their weaknesses. I would not necessarily assume that a statement like "Chazal knew all science" was believed literally by the author, even if he did not contradict it elsewhere in his writings. In contrast, if an orthodox scholar states that Chazal erred in one of their scientific pronouncements, or that they were capable of error, I am inclined to think that he really believes it; for otherwise, his assertion constitutes inexcusable irreverence. This principle will be, I imagine, intuitive to anyone familiar with rabbinic texts.

All things being equal, then, in cases where two passages contradict each other and it seems that one of them does not accurately represent the author's belief, I am more inclined to think that one passage exaggerates Chazal's scientific competence than that the other falsely and gratuitously accuses them of error.

4. Rabbi Dr. Dovid Gottlieb of Ohr Somayach has written an excellent essay entitled "Living Up to the Truth" (available at regarding the grounds for rational belief in the veracity of the Torah and of orthodox Judaism. Very generally, he argues that many ascertained historical facts associated with the Torah are so exceptional and unprecedented as to defy any reasonable natural explanation. It is more rational, he asserts, to assume supernatural intervention as the cause of these historical anomalies; this assumption leads to the conclusion that there is a God, and that God gave the Israelites the Torah. (Obviously, his essay, more than sixty pages long, has hardly been done justice in my two sentences here.) I wish to examine briefly what bearing this approach to belief in Judaism may have on our topic of Chazal's scientific knowledge.

The crux of Rabbi Gottlieb's argument is that although the divinity of the Torah cannot be proven beyond all possibility of refutation, divine authorship is the most reasonable explanation of its provenance. The evidence in favour of divine authorship overwhelms the evidence against it. Thus, although we may have difficulty believing, for example, the Torah's report that manna fell from heaven for forty years to feed the Jews, the alternative – believing that this account in the Torah is false – is even more unreasonable, and we must therefore accept the truth of the Torah's claim.

Let us now perform the following mind experiment. Suppose the Torah said – without allowing for any possibility of interpreting its assertion non-literally – that Bill Clinton had never existed (and never would exist). What impact would this statement have on our assessment of its credibility (and, hence, its divinity)? I propose that the evidence in favour of the existence of Bill Clinton outweighs the evidence Rabbi Gottlieb presents in favour of the Torah's divinity. Thus if acceptance of the Torah's truth requires us to deny the existence of Bill Clinton – as it does, in our case, by construction – we must, if we are rational, reject instead the reliability of the Torah and maintain our belief in Bill Clinton's existence. We will have to find other ways to explain the historical anomalies associated with the Torah.

Suppose now that the Torah – or its extension, Torah Judaism (see Rabbi Gottlieb's essay) – required us to believe that spontaneous generation of living organisms occurs on a regular basis; or, at least, that it did in the times of the Talmud. What impact would this statement have on our assessment of the Torah's credibility (and, hence, its divinity)? We would have to compare the evidence in favour of the Torah's divinity with the evidence against the regular occurrence of spontaneous generation. If the former outweighs the latter, we would conclude that spontaneous generation occurs, evidence to the contrary notwithstanding. Otherwise, we would be forced to accept that the Torah is false, and, again, we would have to explain away the historical evidence Rabbi Gottlieb presents.

I personally assume that Talmudic science was flawed, and understandably so, given that the greatest scientists of the Talmudic era had reached conclusions that later investigations have since disproved. I do not consider the imperfection of Talmudic science to invalidate the bulk of the Torah, the Talmud, or Judaism as a whole, since I do not believe the assumptions of Talmudic science to be part of the indivisible corpus of Jewish dogma that one must either accept or reject in its entirety. The list of sources that follows is partially intended to demonstrate that many of the greatest scholars in the last 1500 years of Jewish history have held the same view.

Technical Remarks

I-D. 1. Hebrew quotations (where provided) sometimes include sentences or even paragraphs that I have not translated into English. I have provided this material in the language of its origin in order to allow the reader to form a more complete impression of the primary source without my interference. Even in Hebrew, however, I have sometimes quoted only part of a paragraph or section where I judged the rest was not essential in the context of this article; my Hebrew typing skills are poor, and I didn't want to spend the time required to copy the rest of the piece.

2. I have provided scholarly translations, with attribution, in cases where I have been able to obtain them. In cases where no translation was available to me, I have, perhaps foolishly, attempted my own. I wish to emphasize that I do not claim my translations to be precise. I have tried to convey the meaning of each passage as best I understand it, and to make the translations smooth, coherent and readable. I have often skipped over or left out sentences or ideas that I did not consider relevant to the topic of this article. I am no expert, and I have no doubt made numerous errors, but I hope that I have at least correctly understood and adequately represented the overall thrust and principal ideas of every text. Any suggestions for improvements in this regard would be greatly appreciated.

3. For the exact names (including their transliterations), life dates and countries of residence of the authorities I cite, I have used a variety of sources, some probably more reliable than others. I would not counsel the reader to rely on this article as a source of precise historical data, though I believe the information to be reasonably accurate. Again, please submit any corrections in the comments.

4. To address some – though not all – of the errors that the blog software makes in displaying Hebrew, I have introduced each quotation with the Hebrew abbreviation ז"ל instead of the colon I would otherwise have placed after the bibliographical information, and I have added עכ"ל after the final punctuation at each quotation's conclusion.


I-E. Many people have personally assisted me in my research of this topic, lending me their knowledge, their wisdom, their libraries, or simply (!) their time, and I am grateful to them all. Here I will give insufficient acknowledgement to those I can think of; a detailed account of how each has been invaluable would quickly become as long as this article itself.

N.B. The reader should draw no conclusions about the opinions of any of the people thanked herebelow. Not everyone whom I thank was aware of why I solicited his assistance; and some people, notwithstanding their help, disagree with the premise of this article, or have no opinion on the matter. My acknowledgement indicates only my gratitude; nothing more.

My parents, who have supported me through thick and thin, must top any list of those to whom I am grateful, always.

I wish first to thank my teacher, Rabbi Eliezer Ben-Porat, who has been an invaluable resource in many ways. It is a true privilege to have ready access to his storehouse of knowledge and wisdom.

Simon Basalely, the indefatigable Menachem Butler, Max Friedman, Shlomo Friedman, Michael Goldstein, Rabbi Micah Shotkin, Rabbi Gil Student, and another person who requested to remain anonymous, have made major contributions, each in his own way, to this compilation.

Dr. Moshe Bernstein, Yitzchak Brand, Ari Brodsky, Avi Brodsky, Rabbi Yonah Burr, Rabbi Baruch Clinton, David Hellman, Drew Kaplan, Dr. Hana Kasher, Dani Raymon, Dr. Benjamin Richler, Dr. Bernard Septimus, Dr. Marc Shapiro, Y. Shapiro, Rabbi Zischa Shaps, “Voldie,” Rabbi Dr. Jeremy Wieder, and Rabbi Netanel Wiederblank have all been helpful (some, perhaps, without realising it).

I thank the following great teachers and leaders of our generation for allowing me the honour and privilege of speaking to them about this topic: Rabbi Ephraim Greenblatt, Rabbi Shmuel Kamenetsky, Rabbi Hershel Schachter, Rabbi Aharon Schechter, and two other great rabbis who requested not to be named. Please note, again, that this acknowledgement should not be taken as an indication of their position on the subject of Chazal and science, or on any other topic.

I wish to express my appreciation also for my extensive use of the libraries of the Jewish Theological Seminary; the Kollel of Ottawa; the Soloway Jewish Community Centre of Ottawa (with special thanks to librarian Estelle Backman); and Yeshiva University. Rabbi Moshe Schapiro, Zalman Alpert and Zvi Erenyi of the Mendel Gottesman Library of Yeshiva University have been superbly helpful in a multitude of ways, and without them much of this article could not have been written.

I apologize to anyone whom I have neglected to mention.
II. Sources from the Talmudic Era


Babylonian Talmud

Berachot 44b

Berachot 44b

Two disputes regarding dietary science:

ברכות מד: (ש"ס ווילנא); ז"ל

וא"ר יצחק כל האוכל ירק קודם ארבע שעות אסור לספר הימנו מאי טעמא משום ריחא וא"ר יצחק אסור לאדם שיאכל ירק חי קודם ארבע שעות אמימר ומר זוטרא ורב אשי הוו יתבי אייתו קמייהו ירק חי קודם ארבע שעות אמימר ורב אשי אכול ומר זוטרא לא אכל אמרו ליה מאי דעתיך דא"ר יצחק כל האוכל ירק קודם ארבע שעות אסור לספר הימנו משום ריחא והא אנן דקא אכלינן וקא משתעית בהדן אמר להו אנא כאידך דר' יצחק ס"ל דא"ר יצחק אסור לאדם שיאכל ירק חי קודם ארבע שעות
תנו רבנן דג קטן מליח פעמים שהוא ממית בשבעה בשבעה עשר ובעשרים ושבעה ואמרי לה בעשרים ושלשה ולא אמרן אלא במטוי ולא מטוי אבל מטוי שפיר לית לן בה ודלא מטוי שפיר לא אמרן אלא דלא שתה בתריה שכרא אבל שתה בתריה שכרא לית לן בה: עכ"ל

R. Isaac also said: If one eats vegetables before the fourth hour [of the day], it is forbidden to talk with him. What is the reason? Because his breath smells. R. Isaac also said: It is forbidden to a man to eat raw vegetables before the fourth hour. Amemar and Mar Zutra and R. Ashi were once sitting together when raw vegetables were set before them before the fourth hour. Amemar and R. Ashi ate, but Mar Zutra would not eat. They said to him: What is your reason? Because R. Isaac said that if one eats vegetables before the fourth hour it is forbidden to converse with him because his breath smells? See, we have been eating, and you have been conversing with us? He replied: I hold with that other saying of R. Isaac, where he said that it is forbidden to a man to eat raw vegetables before the fourth hour [but it is not forbidden to converse with him].
Our Rabbis taught: A small salted fish is sometimes deadly, namely on the seventh, the seventeenth and the twenty-seventh day of its salting. Some say, on the twenty-third. This is the case only if it is imperfectly roasted; but if it is well roasted, there is no harm in it. And even if it is not well roasted there is no harm in it unless one neglects to drink beer after it; but if one drinks beer after it, there is no harm. [translation by Maurice Simon in The Babylonian Talmud, Rabbi Dr. I. Epstein, ed., Seder Zera`im Vol. I (Berakhot), London: Soncino, 1958]

(Reference from Rabbi Micah Shotkin.)

Berachot 58b

Shmuel admits ignorance regarding a certain astronomical question, despite his self-professed expertise on astronomy; amoraim then debate a matter of astronomy:

ברכות נח: (ש"ס ווילנא); ז"ל

על הזיקין: מאי זיקין אמר שמואל כוכבא דשביט ואמר שמואל נהירין לי שבילי דשמיא כשבילי דנהרדעא לבר מכוכבא דשביט דלא ידענא מאי ניהו וגמירי דלא עבר כסלא ואי עבר כסלא חרב עלמא והא קא חזינן דעבר זיויה הוא דעבר ומתחזי כדעבר איהו רב הונא ברי' דרב יהושע אמר וילון הוא דמקרע דמגלגל ומחזי נהורא דרקיעא רב אשי אמר כוכבא הוא דעקר מהאי גיסא דכסלא וחזי ליה חבריה מהך גיסא ומיבעית ומחזי כמאן דעבר.  עכ"ל

What are zikin?  Samuel said: A comet.  Samuel also said: I am as familiar with the paths of heaven as with the streets of Nehardea, with the exception of the comet, about which I am ignorant.  There is a tradition that it never passes through the constellation of Orion, for if it did, the world would be destroyed.  But we have seen it pass through? – Its brightness passed through, which made it appear as if it passed through itself.  R. Huna the son of R. Joshua said: Wilon was torn asunder and rolled up, showing the brightness of Rakia.  R. Ashi said: A star was removed from one side of Orion and a companion star appeared on the other side, and people were bewildered and thought the star had crossed over.  [translation by Maurice Simon in The Babylonian Talmud, Rabbi Dr. I. Epstein, ed., Seder Zera`im Vol. I (Berakhot), London: Soncino, 1958]

(Reference from Landa, Torah and Science, p. 212)

Berachot 59a

Dispute regarding the cause of thunder:

ברכות נט. (ש"ס ווילנא); ז"ל

ועל הרעמים: מאי רעמים אמר שמואל ענני בגלגלא שנאמר קול רעמך בגלגל האירו ברקים תבל רגזה ותרעש הארץ ורבנן אמרי ענני דשפכי מיא להדדי שנאמר לקול תתו המון מים בשמים רב אחא בר יעקב אמר ברקא תקיפא דבריק בעננא ומתבר גזיזי דברזא רב אשי אמר ענני חלחולי מחלחלי ואתי זיקא ומנשב אפומייהו ודמי כזיקא על פום דני ומסתברא כרב אחא בר יעקב דבריק ברקא ומנהמי ענני ואתי מטרא:  עכ"ל

AND OVER THUNDERS [RE`AMIM].  What are RE`AMIM? – Clouds in a whirl, as it says: The voice of Thy thunder was in the whirlwind; the lightning lighted up the world, the earth trembled and shook (Psalms 77:19).  The Rabbis, however, say: The clouds pouring water into one another, as it says: At the sound of His giving a multitude of waters in the heavens (Jeremiah 10:13).  R. Aha b. Jacob said: A powerful lightning flash that strikes the clouds and breaks off hailstones.  R. Ashi said: The clouds are puffed out and a blast of wind comes and blows across the mouth of them and it makes a sound like wind blowing across the mouth of a jar.  The most probable view is that of R. Aha b. Jacob, for the lightning flashes and the clouds rumble and the rain falls.  [translation by Maurice Simon in The Babylonian Talmud, Rabbi Dr. I. Epstein, ed., Seder Zera`im Vol. I (Berakhot), London: Soncino, 1958]

(Reference from Landa: Torah and Science, pp. 258-259)

Shabbat 41a

Rav Zeira listens to Rav Yehudah give medical advice in a bathhouse.  That medical advice is recorded in the Talmud.  Yet, since it was spoken in a bathhouse, it obviously does not qualify as Torah – as the Gemara makes clear.

שבת מא. (ש"ס ווילנא); ז"ל

ר' זירא הוה קא משתמיט מדרב יהודה דבעי למיסק לארעא דישראל דאמר רב יהודה כל העולה מבבל לא"י עובר בעשה שנאמר בבלה יובאו ושמה יהיו אמר איזיל ואשמע מיניה מילתא ואיתי ואיסק אזל אשכחיה דקאי בי באני וקאמר ליה לשמעיה הביאו לי נתר הביאו לי מסרק פתחו פומייכו ואפיקו הבלא ואשתו ממיא דבי באני אמר אילמלא (לא) באתי אלא לשמוע דבר זה דיי בשלמא הביאו נתר הביאו מסרק קמ"ל דברים של חול מותר לאומרם בלשון קדש פתחו פומייכו ואפיקו הבלא נמי כדשמואל דאמר שמואל הבלא מפיק הבלא אלא אשתו מיא דבי באני מאי מעליותא דתניא אכל ולא שתה אכילתו דם וזהו תחילת חולי מעיים אכל ולא הלך ד' אמות אכילתו מרקבת וזהו תחילת ריח רע הנצרך לנקביו ואכל דומה לתנור שהסיקוהו ע"ג אפרו וזהו תחילת ריח זוהמא רחץ בחמין ולא שתה מהן דומה לתנור שהסיקוהו מבחוץ ולא הסיקוהו מבפנים רחץ בחמין ולא נשתטף בצונן דומה לברזל שהכניסוהו לאור ולא הכניסוהו לצונן רחץ ולא סך דומה למים ע"ג חבית:  עכ"ל

R. Zera was evading Rab Judah.  For he [R. Zera] desired to emigrate to Palestine, whereas Rab Judah said, He who emigrates from Babylon to Palestine violates a positive command, for it is said, They shall be carried to Babylon, and there they shall be.  Said he, I will go, hear a teaching from him, return and emigrate.  He went and found him standing at the baths and saying to his attendant, Bring me natron, bring me a comb, open your mouths and expel the heat, and drink of the water of the baths.  Said he, Had I come to hear nought but this, it would suffice me.  As for 'bring me natron, bring me a comb,' it is well: he informs us that secular matters may be said in the Holy Tongue.  'Open your mouths and expel the heat' too is as Samuel.  For Samuel said: Heat expels heat.  But 'drink the water of the baths' – what is the virtue of that? – For it was taught: If one eats without drinking, his eating is blood, and that is the beginning of stomach trouble.  If one eats without walking four cubits [after it], his food rots, and that is the beginning of a foul smell.  One who has a call of nature yet eats is like an oven which  is heated up on top of its ashes, and that is the beginning of perspiration odour.  If one bathes in hot water and drinks none, he is like an oven heated without but not within.  If one bathes in hot water and does not have a cold shower bath, he is like an iron put into fire but not into cold water.  If one bathes without anointing, he is like water [poured] over a barrel.  [translation by Rabbi Dr. H. Freedman in The Babylonian Talmud, Rabbi Dr. I. Epstein, ed., Seder Mo'ed Vol. I (Shabbath I), London: Soncino, 1938]

(Reference from RBP)

Shabbat 85a, Yalkut Shimoni

Shabbat 85a: The sages learned horticultural facts (or at least one) from non-Jewish experts:

שבת פה. (ש"ס ווילנא); ז"ל

וקים להו לרבנן דחמשא בשיתא לא ינקי מהדדי ומנלן דהא דקים להו לרבנן (דחמשא בשיתא) מילתא היא דא"ר חייא בר אבא א"ר יוחנן מאי דכתיב לא תסיג גבול רעך [אשר גבלו ראשונים] גבול שגבלו ראשונים לא תסיג מאי גבלו ראשונים אמר רבי שמואל בר נחמני אמר רבי יונתן (מאי) דכתיב אלה בני שעיר החורי יושבי הארץ אטו כולי עלמא יושבי רקיע נינהו אלא שהיו בקיאין בישובה של ארץ שהיו אומרים מלא קנה זה לגפנים מלא קנה זה לתאנים וחורי שמריחים את הארץ וחוי אמר רב פפא שהיו טועמין את הארץ כחויא.  עכ"ל

The Rabbis ascertained that five [species sown] in six [handbreadths square] do not draw [sustenance] from each other.  And how do we know that that which the Rabbis ascertain is of consequence [to base a law thereon]?  For R. Hiyya b. Abba said in R. Johanan's name: What is meant by, Thou shalt not remove thy neighbour's landmark, which they of old have set (Deuteronomy 19:14)?  The landmark which they of old have set thou shalt not encroach upon.  What landmarks did they of old set?  R. Samuel b. Nahmani said in R. Johanan's name, [Even] as it is written, These are the sons of Seir the Horite, the inhabitants of the earth (Genesis 36:20): are then the whole world inhabitants of heaven?  But it means that they were thoroughly versed in the cultivation of the earth.  For they used to say, This complete [measuring] rod [of land is fit] for olives, this complete [measuring] rod [is fit] for vines, this complete [measuring] rod for figs.  [They know how to divide up the land for cultivation, and as a corollary they must have known how much earth each species required for its sustenance.  It was from them that the Rabbis acquired this knowledge, whose correctness is vouched for by this verse.]  [translation by Rabbi Dr. H. Freedman in The Babylonian Talmud, Rabbi Dr. I. Epstein, ed., Seder Mo'ed Vol. II (Shabbath II), London: Soncino, 1938]

Almost identical passages appear in Yalkut Shimoni in two places: Torah, Parshat Vayishlach, remez 139; and Isaiah, remez 506.

Eruvin 56a

Dispute regarding astronomy:

עירובין נו. (ש"ס ווילנא); ז"ל

רבי יוסי אומר אם אינו יודע לרבעה בריבוע של עולם מרבעה כמין התקופה כיצד חמה יוצאה ביום ארוך ושוקעת ביום ארוך זה הוא פני צפון חמה יוצאה ביום קצר ושוקעת ביום קצר זה הוא פני דרום תקופת ניסן ותקופת תשרי חמה יוצאה בחצי מזרח ושוקעת בחצי מערב שנאמר הולך אל דרום וסובב אל צפון הולך אל דרום ביום וסובב אל צפון בלילה סובב סובב הולך הרוח אלו פני מזרח ופני מערב פעמים מהלכתן ופעמים מסבבתן אמר רב משרשיא ליתנהו להני כללי דתניא לא יצאה חמה מעולם מקרן מזרחית צפונית ושקעה בקרן מערבית צפונית ולא יצאה חמה מקרן מזרחית דרומית ושקעה בקרן מערבית דרומית.  עכ"ל

R. Jose said: If one does not know how to square a town so as to make it correspond with the directions of the world, one may square it in accordance with the circuit of the sun.  How? – The direction in which on a long day the sun rises and sets is the northern direction.  The direction in which on a short day the sun rises and sets is the southern direction.  At the vernal and autumnal equinoxes the sun rises in the middle point of the East and sets in the middle point of the West, as it is said in Scripture, It goeth along the south, and turneth about the north: 'It goeth along the south' during the day 'and turneth about the north' during the night.  The wind turneth, turneth about and moveth refers to the eastern horizon and the western horizon along which the sun sometimes moves and sometimes turns about.

R. Mesharsheya stated: These rules should be disregarded for it was taught: The sun has never exactly risen in the North East and set in the North West, nor has it ever risen precisely in the South East and set in the South West.  [translation by Rev. Dr. Israel W. Slotki in The Babylonian Talmud, Rabbi Dr. I. Epstein, ed., Seder Mo'ed Vol. III (`Erubin), London: Soncino, 1938]

(Reference from Landa, Torah and Science, pp. 114-115)

Eruvin 76a-b

Dispute regarding geometry (just before the first two dots):

עירובין עו.-עו: (ש"ס ווילנא); ז"ל

א"ר יוחנן חלון עגול צריך שיהא בהיקפו עשרים וארבעה טפחים ושנים ומשהו מהן בתוך י' שאם ירבענו נמצא משהו בתוך י' מכדי כל שיש בהיקפו שלשה טפחים יש בו ברוחבו טפח בתריסר סגיא הני מילי בעיגולא אבל בריבועא בעינן טפי מכדי כמה מרובע יתר על העגול רביע בשיתסר סגיא ה"מ עיגולא דנפיק מגו ריבועא אבל ריבועא דנפיק מגו עיגולא בעינן טפי מ"ט משום מורשא דקרנתא מכדי כל אמתא בריבוע אמתא ותרי חומשי באלכסונא בשיבסר נכי חומשא סגיא רבי יוחנן אמר כי דייני דקיסרי ואמרי לה כרבנן דקיסרי דאמרי עיגולא מגו ריבועא ריבעא ריבועא מגו עיגולא פלגא: עכ"ל

R. Johanan ruled: A round window must have a circumference of twenty-four handbreadths, two and a fraction of which must be within ten handbreadths from the ground, so that, when it is squared, a fraction remains within the ten handbreadths from the ground. Consider: Any object that has a circumference of three handbreadths is approximately one handbreadth in diameter: should not then twelve handbreadths suffice? This applies only to a circle, but where a square is to be inscribed within it a greater circumference is required. But observe: By how much does the perimeter of a square exceed that of a circle? By a quarter approximately; should not then a circumference of sixteen handbreadths suffice? This applies only to a circle that is inscribed within the square, but where a square is to be inscribed within a circle it is necessary [for the circumference of the latter] to be much bigger. What is the reason? In order [to allow space for] the projections of the corners. Consider, however, this: Every cubit in [the side of] a square [corresponds to] one and two fifths cubits in its diagonal; [should not then a circumference] of sixteen and four fifths handbreadths suffice? – R. Johanan holds the same view as the judges of Caesarea or, as others say, as that of the Rabbis of Caesarea who maintain [that the area of] a circle that is inscribed within a square is [less than the latter by] a quarter [while that of] the square that is inscribed within that circle [is less than the outer square by] a half. [translation by Rev. Dr. Israel W. Slotki in The Babylonian Talmud, Rabbi Dr. I. Epstein, ed., Seder Mo'ed Vol. III (`Erubin), London: Soncino, 1938]

Pesachim 93b-94a

Rava knew one scientific fact from tradition and another from "sevara"; Rashi: "savar lah midaateih."  Later, tiyuvta of Rava and Ula about geography:

פסחים צג:-צד. (ש"ס ווילנא); ז"ל

אמר עולא מן המודיעים לירושלים חמשה עשר מילין הויא סבר לה כי הא דאמר רבה בר בר חנה אמר רבי יוחנן כמה מהלך אדם ביום עשרה פרסאות מעלות השחר ועד הנץ החמה חמשת מילין משקיעת החמה ועד צאת הכוכבים חמשת מילין פשו לה תלתין חמיסר מצפרא לפלגא דיומא וחמיסר מפלגא דיומא לאורתא עולא לטעמיה דאמר עולא אי זה הוא דרך רחוקה כל שאין יכול ליכנס בשעת שחיטה אמר מר מעלות השחר עד הנץ החמה חמשת מילין מנא לן דכתיב וכמו השחר עלה ויאיצו המלאכים וגו' וכתיב השמש יצא על הארץ ולוט בא צוערה ואמר רבי חנינא לדידי חזי לי ההוא אתרא והויא חמשה מילין
אמר רבא שיתא אלפי פרסי הוי עלמא וסומכא דרקיעא אלפא פרסי חדא גמרא וחדא סברא סבר לה כי הא דאמר רבה בר בר חנה א"ר יוחנן כמה מהלך אדם בינוני ביום י' פרסאות מעלות השחר ועד הנץ החמה ה' מילין משקיעת החמה עד צאת הכוכבים חמשה מילין נמצא עוביו של רקיע אחד מששים ביום מיתיבי רבי יהודה אומר עוביו של רקיע אחד מעשרה ביום תדע כמה מהלך אדם בינוני ביום עשר פרסאות ומעלות השחר עד הנץ החמה ארבעת מילין משקיעת החמה ועד צאת הכוכבים ארבעת מילין נמצאת עוביו של רקיע אחד מעשרה ביום תיובתא דרבא תיובתא דעולא תיובתא לימא תיהוי תיובתא דר' יוחנן אמר לך אנא ביממא הוא דאמרי ורבנן הוא דקא טעו דקא חשבן דקדמא וחשוכא לימא תיהוי תיובתא דרבי חנינא לא ויאיצו שאני ... עכ"ל

`Ulla said: From Modi'im to Jerusalem is fifteen miles.  He holds as Rabbah b. Bar Hanah said in R. Johanan's name: what is an [average] man's journey in a day?  Ten parasangs: five mils from daybreak until the first sparklings of the rising sun, [and] five mils from sunset until the stars appear.  This leaves thirty: fifteen from the morning until midday, and fifteen from midday until evening [i.e., sunset].  `Ulla is consistent with his view, for `Ulla said: What is 'a journey afar off'?  Any place whence a man is unable to enter [Jerusalem] at the time of slaughtering.

The Master said: 'Five mils from daybreak until the first sparklings of the rising sun.'  Whence do we know it? – Because it is written, And when the morning arose [i.e., at daybreak], then the angels hastened Lot, etc.; and it is written, The sun was risen upon the earth when Lot came unto Zoar; while R. Hanina said: I myself saw that place and it is five mils [from Sodom].
Raba said: The world is six thousand parasangs, and the thickness of the heaven [rakia`] is one thousand parasangs the first one [of these statements] is a tradition, while the other is [based on] reason.  [Thus:] he agrees with Rabbah b. Hanah's dictum in R. Johanan's name: What is an average man's journey in a day?  Ten parasangs: from daybreak until the first sparklings of the rising sun five mils, and from sunset until the stars appear five mils: hence the thickness of the heaven is one sixth of the day['s journey].

An objection is raised: Rab Judah said: The thickness of the sky is one tenth of the day's journey.  The proof is this: what is an [average] man's journey in a day?  Ten parasangs, and from daybreak until the rising sun four mils, [and] from sunset until the stars appear four mils: hence the thickness of the sky is one tenth of the day['s journey].  This is a refutation of Raba, and a refutation of `Ulla!  It is a refutation.  Shall we say that this is [also] a refutation of R. Johanan? – He can answer you: I spoke only of [an average man's journey] in a [complete] day, and it was the Rabbis who erred by calculating [the distance for] pre-dawn and after nightfall.  Shall we say that this is a refutation of R. Hanina? – No: 'and [the angels] hastened' is different.  [translation by Rabbi Dr. H. Freedman in The Babylonian Talmud, Rabbi Dr. I. Epstein, ed., Seder Mo'ed Vol. IV (Pesahim), London: Soncino, 1938]

Pesachim 93b-94b contain many seeming contradictions to the notion that Chazal could not make scientific errors.  So does Chap. 3 of Chullin, including 45b.

Pesachim 94b

Rabbi Yehudah Hanasi says that the gentiles' scientific theory is more probably correct than Chazal's:

פסחים צד: (ש"ס ווילנא); ז"ל

חכמי ישראל אומרים ביום חמה מהלכת למטה מן הרקיע ובלילה למעלה מן הרקיע וחכמי אומות העולם אומרים ביום חמה מהלכת למטה מן הרקיע ובלילה למטה מן הקרקע א"ר ונראין דבריהן מדברינו שביום מעינות צוננין ובלילה רותחין.  עכ"ל

The Sages of Israel maintain: The sun travels beneath the sky by day and above the sky at night; while the Sages of the nations of the world maintain: It travels beneath the sky by day and below the earth at night.  Said Rabbi: And their view is preferable to ours, for the wells are cold by day but warm at night.  [translation by Rabbi Dr. H. Freedman in The Babylonian Talmud, Rabbi Dr. I. Epstein, ed., Seder Mo'ed Vol. IV (Pesahim), London: Soncino, 1938]

Sukkah 8a-b

The Gemara rejects the geometric views of the dayanei dekeisari:

סוכה ח.-ח: (ש"ס ווילנא); ז"ל

רבנן דקיסרי ואמרי לה דייני דקיסרי אמרי עיגולא דנפיק מגו ריבועא רבעא ריבועא דנפיק מגו עיגולא פלגא ולא היא דהא קחזינן דלא הוי כולי האי:  עכ"ל

The Rabbis of Caesarea (and some say, The judges of Caesarea) maintain, The circumference of a circle inscribed in a square is a quarter [i.e., a quarter less than the perimeter of the square]; but the square inscribed within that circle is a half.  But this is not correct, for we see that these are not so much bigger.  [translation by Rev. Dr. Israel W. Slotki in The Babylonian Talmud, Rabbi Dr. I. Epstein, ed., Seder Mo'ed Vol. VI (Sukkah-Bezah), London: Soncino, 1938]

Ta'anit 9b-10a, Eruvin 45b

Dispute regarding meteorology at Ta'anit 9b-10a:

תענית ט:-י. (ש"ס ווילנא); ז"ל

תניא ר' אליעזר אוצר כל העולם כולו ממימי אוקיינוס הוא שותה שנאמר ואד יעלה מן הארץ והשקה את כל פני האדמה אמר לו ר' יהושע והלא מימי אוקיינוס מלוחין הן אמר לו ממתקין בעבים ר' יהושע אומר כל העולם כולו ממים העליונים הוא שותה שנאמר למטר השמים תשתה מים אלא מה אני מקיים ואד יעלה מן הארץ מלמד שהעננים מתגברים ועולים לרקיע ופותחין פיהן כנוד ומקבלין מי מטר שנאמר יזקו מטר לאדו ומנוקבות הן ככברה ובאות ומחשרות מים על גבי קרקע שנאמר חשרת מים עבי שחקים ואין בין טיפה לטיפה אלא כמלא נימא ללמדך שגדול יום הגשמים כיום שנבראו בו שמים וארץ שנאמר עושה גדולות עד אין חקר וכתיב הנותן מטר על פני ארץ וכתיב להלן הלא ידעת אם לא שמעת אל[ק]י עולם ה' אין חקר לתבונתו (וכתיב מכין הרים בכחו וגו') כמאן אזלא הא דכתיב משקה הרים מעליותיו וא"ר יוחנן מעליותיו של הקב"ה כמאן כרבי יהושע ור' אליעזר כיון דסלקי להתם משקה מעליותיו קרי להו דאי לא תימא הכי אבק ועפר מן השמים היכי משכחת לה אלא כיון דמדלי להתם מן השמים קרי ליה הכא נמי כיון דסלקי להתם מעליותיו קרי ליה כמאן אזלא [הא] דא"ר חנינא כונס כנד מי הים נותן באוצרות תהומות מי גרם לאוצרות שיתמלאו בר תהומות כרבי אליעזר ור' יהושע ההוא בברייתו של עולם.  עכ"ל

It has been taught: R. Eliezer said: The whole world draws its water supply from the waters of the ocean, as it is said, But there went up a mist from the earth and watered the whole of the ground (Genesis 2:6).  Thereupon R. Joshua said to him: But are not the waters of the ocean salty?  He replied: They are sweeteend by the clouds.  R. Joshua said: The whole world drinks from the upper waters, as it is said, And drinketh water as the rain of heaven cometh down (Deuteronomy 11:11).  If so, what is the force of the verse, 'But there went up a mist from the earth`?  This teaches that the clouds grow in strength as they rise towards the firmament and then open their mouth as a flask and catch the rain water, as it is said, Which distil rain from His vapour (Job 36:27); they are perforated like a sieve and they slowly distil [mehashroth] waters on the ground, as it is said, Distilling [hashroth] of waters, thick clouds of the skies (II Samuel 22:12); there is but one hand-breadth space between one drop and another, in order to teach you that the day on which rain falls is as great as the day whereon heaven and earth were created, as it is said, Who doeth great things past finding out (Job 5:9); and it is written, Who giveth rain upon the earth (Job 5:10); and it is also written, Hast thou not known? hast thou not heard that the everlasting God, the Lord ... Is discernment is past finding out (Isaiah 40:28)?

Whose view is supported by the verse, Who waterest the mountains from Thine upper chambers (Psalms 104:13), which R. Johanan interprets to mean the upper chambers of the Almighty?  Whose view? – It is that of R. Joshua.  And R. Eliezer's view? – As [the waters] ultimately find their way above [Scripture] aptly terms them, 'from thine upper chambers'.  For if it were not so, how will you explain, Powder and dust from heaven (Deuteronomy 28:24)?  What you must [say is] that as these rise upwards [from the ground] the words, 'from heaven' are quite aptly applied to them.  Likewise as the waters eventually find their way above Scripture aptly refers to them as, 'from Thine upper chambers'.  Whose view supports R. Hanina who said this, He gathereth the waters of the sea together as a heap; He layeth up the deeps in storehouses (Psalms 33:7), [as meaning,] Who caused the storehouses to be filled with grain?  The deeps – the view of R. Eliezer.  And what of R. Joshua's [view]? – That [verse] refers to Creation of the world.  [translation by Rev. Dr. J. Rabbinowitz in The Babylonian Talmud, Rabbi Dr. I. Epstein, ed., Seder Mo'ed Vol. VII (Rosh Hashanah-Ta`anith-Shekalim), London: Soncino, 1938]

The Gemara makes reference to this dispute at Eruvin 45b as well:

עירובין מה: (ש"ס ווילנא); ז"ל

אמר מר ביום טוב הרי הן כרגלי כל אדם ואמאי ליקני שביתה באוקיינוס לימא דלא כרבי אליעזר דאי כר' אליעזר הא אמר כל העולם כולו ממי אוקיינוס הוא שותה אמר ר' יצחק הכא בעבים שנתקשרו מערב יום טוב עסקינן ודילמא הנך אזלי והנך אחריני נינהו דאית להו סימנא בגוייהו ואיבעית אימא הוי ספק דדבריהם וספק דדבריהם להקל.  עכ"ל

The Master said: 'If [it fell] on a festival day the water is on a par with the feet of every man'.  But why?  Should not the rain water acquire its place for the Sabbath in the ocean?  Must it then be assumed that this ruling is not in agreement with the view of R. Eliezer?  For if it were in agreement with R. Eliezer [the objection world arise:] Did he not state that all the world drinks from the water of the ocean? – R. Isaac replied: Here we are dealing with a case where the clouds were formed on the eve of the festival.  But is it not possible that those moved away and these are others? – It is a case where one can recognize them by some identification mark.  And if you prefer I might reply: This is a matter of doubt in respect of a Rabbinical law and in any such doubt a lenient ruling is adopted.  [translation by Rev. Dr. Israel W. Slotki in The Babylonian Talmud, Rabbi Dr. I. Epstein, ed., Seder Mo'ed Vol. III (`Erubin), London: Soncino, 1938]

(Reference from Landa: Torah and Science, pp. 255-257)

Chagigah 12b

Dispute regarding the composition of the sky (possibly allegorical):

חגיגה יב: (ש"ס ווילנא); ז"ל

א"ר יהודה שני רקיעים הן שנאמר הן לה' אל[ק]יך השמים ושמי השמים ר"ל אמר שבעה ואלו הן וילון רקיע שחקים זבול מעון מכון ערבות וילון אינו משמש כלום אלא נכנס שחרית ויוצא ערבית ומחדש בכל יום מעשה בראשית שנאמר הנוטה כדוק שמים וימתחם כאהל לשבת רקיע שבו חמה ולבנה כוכבים ומזלות קבועין שנאמר ויתן אותם אל[ק]ים ברקיע השמים....  עכ"ל

R. Judah said: There are two firmaments, for it is said: Behold, unto the Lord thy God belongeth heaven, and the heaven of heavens.  Resh Lakish said: [There are] seven, namely, Wilon, Rakia`, Shehakim, Zebul, Ma`on, Makon, `Araboth.  Wilon serves no purpose except that it enters in the morning and goes forth in the evening, and renews every day the work of creation, for it is said: That stretcheth out the heavens as a curtain, and spreadeth them out as a tent to dwell in.  Rakia` is that in which sun and moon, stars and constellations are set, for it is said: And God set them in the firmament [Rakia`] of the heaven....  [translation by Rabbi Prof. I. Abrahams in The Babylonian Talmud, Rabbi Dr. I. Epstein, ed., Seder Mo'ed Vol. VIII (Megillah-Mo`ed Katan-Hagigah), London: Soncino, 1938]

(Reference from Landa: Torah and Science, p. 66)

Nazir 52a

The sages relied on physicians' expertise to render a halachic ruling:

נזיר נב. (ש"ס ווילנא); ז"ל

תא שמע רבי יהודה אומר ששה דברים ר' עקיבא מטמא וחכמים מטהרין וחזר בו ר' עקיבא ומעשה שהביאו קופה מלאה עצמות לבהכ"נ של טרסיים והניחוה באויר ונכנס תודוס הרופא וכל הרופאים [עמו] ואמרו אין כאן שדרה ממת אחד טעמא דליכא שדרה דמחדא האיכא או שדרה או גולגולת דמחדא נזיר מגלח עליה ש"מ או שדרה או גולגולת תנן לא מיבעיא קאמר לא מיבעיא שדרה וגולגולת דממת אחד ליכא אלא אפי' או שדרה ממת אחד או גולגולת ממת אחד ליכא... עכ"ל

Come and hear: R. Judah says: Six things were declared unclean by R. Akiba and clean by the Sages, and R. Akiba retracted his opinion. It is related that a basket full of [human] bones was taken into the Synagogue of the Tarsians and placed in the open air. The Theodos, the Physician, together with all the physicians, entered, and said that there was not the backbone of a single corpse there. The reason [that it was declared clean] is that there was not a backbone from a single [corpse], but had there been either a backbone or a skull from a single [corpse], a nazirite would have been required to poll because of it, whence it follows that we read in our Mishnah, either the backbone or the skull? - The case was put strongly. Not only was there not the backbone and skull of a single corpse, but there was not even the backbone of a single corpse or the skull of a single corpse. [translation from The Babylonian Talmud, Seder Nashim Vol. VI (Nazir-Sotah), Nazir, the Rev. Dr. A. Cohen, trans. London: Soncino, 1936]

(Reference from Rabbi Gil Student, "The Approach of the Talmudic Sages to Science," available at

Sotah 3b-4a, 4b

On Sotah 3b-4a, tannaim argue regarding the minimum length of time required for human sexual relations.  The Gemara explains, on Sotah 4b, that their dispute was based on their own personal experience.  Also on 4b, the Gemara questions how Ben Azai (who is initially assumed to have been a bachelor all his life) could have opined on the matter (which he did).  The Gemara proposes several answers, not all of which involve his having derived his knowledge from the Torah:

סוטה ג:-ד: (ש"ס ווילנא); ז"ל

תנו רבנן אי זו היא עדות הראשונה זו עדות סתירה עדות אחרונה זו עדות טומאה וכמה שיעור סתירה כדי טומאה כדי ביאה כדי העראה כדי הקפת דקל דברי רבי ישמעאל ר"א אומר כדי מזיגת הכוס רבי יהושע אומר כדי לשתותו בן עזאי אומר כדי לצלות ביצה ר"ע אומר כדי לגומעה רבי יהודה בן בתירא אומר כדי לגמוע שלש ביצים זו אחר זו ר"א בן ירמיה אומר כדי לקשור גרדי נימא חנין בן פנחס אומר כדי שתושיט ידה לתוך פיה ליטול קיסם פלימו אומר כדי שתושיט ידה לסל ליטול ככר
א"ר יצחק בר (רב) יוסף א"ר יוחנן כל אחד ואחד בעצמו שיער והאיכא בן עזאי דלא נסיב איבעית אימא נסיב ופירש הוה ואיבעית אימא מרביה שמיע ליה ואיבעית אימא סוד ה' ליראיו.  עכ"ל

Our Rabbis have taught: Which is the 'first testimony'?  Evidence of seculsion, and the 'final testimony' is evidence of 'defilement' [misconduct].  And how long is the duration in the matter of seclusion?  Sufficient for misconduct, i.e., sufficient for coition, i.e., sufficient for sexual contact, i.e., sufficient for a person to walk round a date-palm.  Such is the view of R. Ishmael; R. Eliezer says: Sufficient for preparing a cup of wine; R. Joshua says: Sufficient to drink it; Ben Azzai says: Sufficient to roast an egg; R. Akiba says: Sufficient to swallow it; R. Judah b. Bathyra says: Sufficient to swallow three eggs one after the other; R. Eleazar b. Jeremiah says: Sufficient for a weaver to knot a thread; Hanin b. Phineas says: Sufficient for a woman to extend her hand to her mouth to remove a chip of wood [from between the teeth]; Pelemo says: Sufficient for her to extend her hand to a basket and take a loaf therefrom.
R. Isaac son of R. Joseph said in the name of R. Johanan: Each of the teachers defined the duration [of coition] from his own experience.  But they included Ben Azzai who was unmarried!  – If you wish I can say that he had married and separated [from his wife], or that he had heard it from his master, or that The secret of the Lord is with them that fear him.  [translation by The Rev. Dr. A. Cohen in The Babylonian Talmud, Rabbi Dr. I. Epstein, ed., Seder Nashim Vol. VI (Nazir-Sotah), London: Soncino, 1936]

(Reference from Levi, Facing Current Challenges, Chap. 33, fn. 24)

Sotah 10a

The Gemara proposes several possible reasons as to why Rav Nachman could describe the symptoms of a particular illness; not all of them involve his having derived his knowledge from the Torah:

סוטה י. (ש"ס ווילנא); ז"ל

א"ל מר זוטרא בריה דרב נחמן לרב נחמן היכי דמי פדגרא א"ל כמחט בבשר החי מנא ידע איכא דאמרי מיחש הוה חש ביה ואיכא דאמרי מרביה שמע ליה וא"ד סוד ה' ליראיו ובריתו להודיעם.  עכ"ל

Mar Zutra, son of R. Nahman, asked R. Nahman, What is Podagra like? – He answered, Like a needle in living flesh.  How did he know this? – Some say he suffered from it himself; others say that he heard it fro his teacher; and others declare, The secret of the Lord is with them that fear Him, and He will shew them His covenant.  [translation by The Rev. Dr. A. Cohen in The Babylonian Talmud, Rabbi Dr. I. Epstein, ed., Seder Nashim Vol. VI (Nazir-Sotah), London: Soncino, 1936]

(Reference from Levi, Facing Current Challenges, Chap. 33, fn. 24)

Saturday, April 29, 2006

Sanhedrin 5a-b

Rav states that he spent 18 months living with a shepherd in order to be able to distinguish permanent blemishes from temporary ones; Rabbah bar Chanah was not as familiar with tereifos as Rav, but was judged by Rabbi Yehudah Hanasi to be sufficiently competent to paskan on the issue (and to get smicha). Clearly not all amoraim were on equal footing when it came to scientific knowledge; some were more liable to err than others. That implies they could err.

סנהדרין ה.-ה: (ש"ס ווילנא); ז"ל

כי הוה נחית רבה בר חנה לבבל אמר ליה רבי חייא לרבי בן אחי יורד לבבל יורה יורה ידין ידין יתיר בכורות יתיר כי הוה נחית רב לבבל אמר ליה רבי חייא לר' בן אחותי יורד לבבל יורה יורה ידין ידין יתיר בכורות אל יתיר מ"ש למר דקא קרי בן אחי ומ"ש למר דקא קרי בן אחותי וכי תימא הכי הוה מעשה והאמר מר איבו וחנה ושילא ומרתא ורבי חייא כולהו בני אבא בר אחא כרסלא מכפרי הוו רב בר אחוה דהוה בר אחתיה רבה בר חנה בר אחוה דלאו בר אחתיה ואי בעית אימא על שם חכמתו דכתיב אמור לחכמה אחותי את יתיר בכורות אל יתיר מאי טעמא אילימא משום דלא חכים הא קא אמרינן דחכים טובא אלא משום דלא בקיע במומי והאמר רב שמונה עשר חדשים גדלתי אצל רועה בהמה לידע איזה מום קבוע ואיזה מום עובר אלא לחלק לו כבוד לרבה בר חנה ואיבעית אימא משום הא גופיה דרב בקיע במומי טפי ושרי מומי דלא ידעי אינשי ואמרי כי האי גוונא שרא רב ואתו למשרי מום עובר.  עכ"ל

When Rabbah b. Hana was about to go to Babylon, R. Hiyya said to Rabbi: ... 'May he declare firstborn animals permissible [for slaughter]?' – [Rabbi answered:] 'He may.'  When Rab went there, R. Hiyya said to Rabbi: ... "May he declare firstborn animals permissible for slaughter?' – [Rabbi answered:] 'He may not.' ... What was the reason that Rab was not authorised to permit the slaughter of firstborn animals? ... Was it because he was not an expert in judging defects?  But did not Rab himself say: I spent eighteen months eith a shepherd in order to learn which was a permanent and which a passing blemish? – Rabbi withheld that authorisation from Rab, as a special mark of respect to Rabbah b. Hana [so as to establish him firmly in the respect of the Babylonians, whilst Rab's standing was in any case high].  [translation by Jacob Schachter in The Babylonian Talmud, Rabbi Dr. I. Epstein, ed., Seder Nezikin Vol. V (Sanhedrin I), London: Soncino, 1935]

Makot 5b

Rabbi Yehudah ben Tabai, a tanna with (real) smicha, has someone wrongfully executed because he was ignorant of a certain halacha.  (The only relevance of this passage to the topic of this article is that it indicates that even tannaim musmachim did not possess perfect knowledge – not even of halacha.)

מכות ה: (ש"ס ווילנא); ז"ל

תניא אמר רבי יהודה בן טבאי אראה בנחמה אם לא הרגתי עד זומם להוציא מלבן של צדוקים שהיו אין העדים זוממין נהרגין עד שיהרג הנדון אמר לו שמעון בן שטח אראה בנחמה אם לא שפכת דם נקי שהרי אמרו חכמים אין העדים זוממין נהרגין עד שיזומו שניהם ואין לוקין עד שיזומו שניהם מיד קבל עליו ר' יהודה בן טבאי שאינו מורה הוראה אלא לפני שמעון בן שטח וכל ימיו של ר' יהודה בן טבאי היה משתטח על קברו של אותו העד והיה קולו נשמע וכסבורין העם לומר קולו של הרוג אמר קולי שלי הוא תדעו למחר הוא מת אין קולו נשמע אמר ליה רב אחא בריה דרבא לרב אשי דלמא בדינא קם בהדיה אי נמי פיוסי פייסיה:  עכ"ל

It has been taught: R. Judah b. Tabbai said: 'May I [never] see consolation [of Israel] if I did not have one zomem-witness done to death to disabuse the mind of the Sadducees, who used to say that zomemim [found guilty] were put to death only after the [falsely] accused person had [actually] been executed.'  Said Simeon b. Shetah to him: 'May I [never] see consolation [of Israel] if you have not shed innocent blood because the Sages declared that witnesses found to be zomemim are not put to death until both have been proved as such, and are not [juridically] flogged until both have been proved as such.'  Forthwith did Judah b. Tabbai take upon himself a resolve never to deliver a decision save in the presence of Simeon b. Shetah.  And all through his [remaining] days, Judah b. Tabbai used to go and prostrate himself on the grave of that [slain] witness, and his voice would be heard and people thought that it was the voice of the slain man; but he would tell them, 'It is my voice!  You will be convinced when on the morrow of this man's [his own] death his voice will be heard no more'.

Said R. Aha, the son of Raba, to R. Ashi: He might perhaps have answered the summons of the deceased, or else he might have obtained his forgiveness.  [translation by H. M. Lazarus in The Babylonian Talmud, Rabbi Dr. I. Epstein, ed., Seder Nezikin Vol. VIII (Shebu`oth–Makkoth-Eduyyoth–Aboth), London: Soncino, 1935]

Avoda Zara 27b-28a

Various amoraim, including Rabbi Yochanan and Abayei, relied on non-Jews for medical knowledge and treatment:

עבודה זרה כז:-כח. (ש"ס ווילנא); ז"ל

אמר רבה בר בר חנה אמר רבי יוחנן כל מכה שמחללין עליה את השבת אין מתרפאין מהן ואיכא דאמרי אמר רבה בר בר חנה אמר ר"י כל מכה של חלל אין מתרפאין מהן מאי בינייהו איכא בינייהו גב היד וגב הרגל דאמר רב אדא בר מתנה אמר רב גב היד וגב הרגל הרי הן כמכה של חלל ומחללין עליהן את השבת אמר רב זוטרא בר טוביה אמר רב כל מכה שצריכה אומד מחללין עליה את השבת אמר רב שמן בר אבא אמר ר' יוחנן והאי אישתא צמירתא כמכה של חלל דמי ומחללין עליה את השבת מהיכן מכה של חלל פירש רבי אמי מן השפה ולפנים בעי רבי אליעזר ככי ושיני מאי כיון דאקושי נינהו כמכה דבראי דמו או דילמא כיון דגואי קיימי כמכה של חלל דמו אמר אביי ת"ש החושש בשיניו לא יגמע בהן את החומץ חושש הוא דלא הא כאיב ליה טובא שפיר דמי דלמא תנא היכא דכאיב ליה טובא חושש נמי קרי ליה ת"ש רבי יוחנן חש בצפדינא אזל לגבה דההיא מטרוניתא עבדה חמשא ומעלי שבתא א"ל למחר מאי אמרה ליה לא צריכת אי צריכנא מאי אמרה אשתבע לי דלא מגלית אישתבע לה לאלהא ישראל לא מגלינא גלייה ליה למחר נפק דרשה בפירקא והא אישתבע לה לאלהא דישראל לא מגלינא אבל לעמיה ישראל מגלינא והאיכא חילול השם דגלי לה מעיקרא אלמא כמכה של חלל דמיא אמר רב נחמן בר יצחק שאני צפדינא הואיל ומתחיל בפה וגומר בבני מעיים מאי סימניה רמי מידי בי ככי ומייתי דמא מבי דרי ממאי הוי מקרירי קרירי דחיטי ומחמימי חמימי דשערי ומשיורי כסא דהרסנא מאי עבדא ליה א"ר אחא בריה דרבא מי שאור ושמן זית ומלח ומר בר רב אשי אמר משחא דאווזא בגדפא דאווזא אמר אביי אנא עבדי כולהו ולא איתסאי עד דאמר לי ההוא טייעא אייתי קשייתא דזיתא דלא מלו תילתא וקלנהו אמרא חדתא ודביק ביה דדרי עבדי הכי ואיתסאי ורבי יוחנן היכי עביד הכי והאמר רבה בר בר חנה אמר רבי יוחנן כל מכה שמחללין עליה את השבת אין מתרפאין מהן אדם חשוב שאני והא רבי אבהו דאדם חשוב הוה ורמא ליה יעקב מינאה סמא אשקיה ואי לא רבי אמי ורבי אסי דלחכוהו לשקיה פסקיה לשקיה דרבי יוחנן רופא מומחה הוה דרבי אבהו נמי רופא מומחה הוה שאני רבי אבהו דמוקמי ביה מיני בנפשייהו תמות נפשי עם פלשתים ... עכ"ל

Said Rabba b. Bar Hanah in the name of R. Johanan: Any sore for which the Sabbath may be profaned should not be healed by a heathen. Others report that Rabba b. Bar Hanah said: Any internal sore should not be healed by them. Wherein do these versions differ? - They differ in the case of a swelling of the hand or a swelling of the foot. For R. Adda b. Mattena said in the name of Rab: A swelling of the hand or a swelling of the foot is to be regarded as [serious as] an internal sore, and the Sabbath may be profaned for it. Said R. Zutra b. Tobiah in the name of Rab: Any sore which requires [medical] opinion justifies the profanation of the Sabbath. R. Shaman b. Abba said in the name of R. Johanan: The inflammatory fever is to be regarded as an internal sore for which the Sabbath may be profaned. Which sore is to be termed internal? R. Ammi explained: [Such as are] on the lip and inward. R. Eleazar asked: How about the gums and the teeth: should they, being hard, be regarded as external; or do we say that, since they are placed within [the mouth], they are to be regarded as internal? - Said Abaye: Come and hear: One who is troubled with his teeth must not rinse them with vinegar [on the Sabbath]. [Which means that] if he is only 'troubled' he must not [rinse them] but if they hurt him very much it is proper [for him to do it]! - Probably this Tanna would call 'being troubled' even if they hurt very much. Then come and hear this: R. Johanan was troubled with scurvy [on his gums] and he went to a certain [heathen] lady who attended to him on the Thursday and the Friday. Said he: What about to morrow? She replied: You will not need [the treatment]. But what if I do need it? he asked. She replied: Swear unto me that you will not reveal [the remedy]. Said he: I swear, to the God of Israel I will not reveal it. She then divulged it to him and on the morrow he referred to it in the course of lecturing. But did he not swear unto her? - He swore: 'To the God of Israel I will not reveal it,' [implying that] I may reveal it to His people Israel. But is this not a profanation of the Name? He mentioned [that proviso] to her originally. Now is it not evident then that a sore on the gum is regarded as an internal sore? - Said R. Nahman b. Isaac: Scurvy is different, because though starting in the mouth it extends to the intestines. What is its symptom? - If he places anything between his teeth, blood comes from the gums. What brings it on? - The chill of cold wheat-food and the heat of hot barley-food, also the remnant of fish-hash and flour. What did she apply to it? - Said R. Aha the son of Raba: Leaven-water with olive oil and salt. Mar son of R. Ashi said: Geese-fat smeared with a goose-quill. Said Abaye: I did all this but was not cured, until a certain Arab told me to get seeds of an olive not one third ripe and burn them on a new spade and spread [the ashes] on the gums; which I did and was cured. But how came R. Johanan to act as he did: had not Rabba b. Bar Hanah said in the name of R. Johanan: Any sore for which the Sabbath may be profaned should not be healed by a heathen? - It is different with a distinguished man [such as R. Johanan was; as the heathen would be afraid to commit any foul play]. What about R. Abbahu, who too was a distinguished man, yet Jacob the Min prepared for him a medicine for his leg, and were it not for R. Ammi and R. Asi who licked his leg, he would have cut his leg off? - The one [who attended] R. Johanan was an expert physician. - So too was that of R. Abbahu, an expert physician! - It was different in the case of R. Abbahu, for Minim adopt the attitude of let me die with the Philistines. [translation by A. Mishcon in The Babylonian Talmud, Rabbi Dr. I. Epstein, ed., Seder Nezikin Vol. VII (`Abodah Zarah-Horayoth), London: Soncino, 1935]

(Reference from Rabbi Gil Student, "The Approach of the Talmudic Sages to Science," at

Chullin 57a

Rabbi Yosei berabi Chanina says that [the amora] Chizkiya erred, out of ignorance, in a statement about biology:

חולין נז. (ש"ס ווילנא); ז"ל

חזקיה אמר אין ריאה לעוף ור' יוחנן אמר יש לו וישנה כעלה של וורד בין אגפים מאי אין ריאה לעוף אילימא דלית ליה כלל והא קא חזינא דאית ליה אלא דלא מיטריף ביה והתני לוי טרפות שמנו חכמים בבהמה כנגדן בעוף יתר עליהן עוף נשבר העצם אע"פ שלא ניקב קרום של מוח אלא אין לו לא לינפל ולא ליחמר מ"ט אמר רב חנה הואיל ורוב צלעותיה מגינות עליה והא מדא"ר יוחנן יש לו וישנה כעלה של וורד בין אגפיים מכלל דחזקיה סבר דלית ליה אלא אמרי במערבא משמיה דר' יוסי ברבי חנינא מדבריו של בריבי ניכר שאינו בקי בתרנגולין: עכ"ל

Hezekiah stated, A bird has no lungs. R. Johanan said, It has [lungs] and they are like rose petals situated immediately beneath the wings. What is meant by, ‘A bird has no lungs’? Does it mean that it has no lungs at all? But we see that it has! And should it mean that any defect therein would not render trefah? Surely Levi has taught: The defects enumerated by the Sages in the case of cattle apply also to birds, with this addition in the case of birds, namely, If the bone [of the skull] was broken even though the membrane of the brain has not been pierced! – We must therefore say that the statement ‘It has no lungs’ means that they are in no wise affected, whether the bird falls down [from the roof] or is scorched [in the fire]. Why is it so? – R. Hannah answered, Because they are protected by most of the ribs. But surely since R. Johanan has said that it has [lungs] and they are like rose petals situated immediately beneath the wings, it follows that Hezekiah was of the opinion that it has no [lungs] at all! – In truth, it has been said in the West in the name of R. Jose, son of R. Hanina, ‘It is evident from the statement of Beribbi [Hezekiah] that he knew nothing of fowls’.

[translation by Eli Cashdan in The Babylonian Talmud, Rabbi Dr. I. Epstein, ed., Seder Kodashim Vol. III (Hullin I), London: Soncino, 1948]

Chullin 57b

Rabbi Shimon ben Chalafta performed a scientific experiment to prove Rabbi Yehudah wrong. This indicates both that Tannaim assigned weight to empirical evidence and that Rabbi Shimon ben Chalafta and Rabbi Yehudah disputed a scientific point.  Later on that page, Tannaim dispute matters of biology, and Rabbi Yosei ben Hameshullam quotes empirical evidence to prove a scientific point.

חולין נז: (ש"ס ווילנא); ז"ל

אמרו עליו על רבי שמעון בן חלפתא שעסקן בדברים היה והיה עושה דבר להוציא מלבו של רבי יהודה שהיה רבי יהודה אומר אם ניטלה הנוצה פסולה ותרנגולת היתה לו לרבי שמעון בן חלפתא שניטלה נוצה שלה והניחה בתנור וטלה עליה במטלית של טרסיים וגידלה כנפיים האחרונים יותר מן הראשונים.
אמר רב הונא סימן לטריפה י"ב חדש מיתיבי סימן לטרפה כל שאינה יולדת רשב"ג אומר משבחת והולכת בידוע שהיא כשרה מתנוונה והולכת בידוע שהיא טרפה רבי אומר סימן לטרפה שלשים יום אמרו לו והלא הרבה מתקיימות שתים שלש שנים תנאי היא דתניא ובגלגלת (עד) שיש בה נקב אחד ארוך אפילו נקבים הרבה מצטרפים למלא מקדח א"ר יוסי בן המשולם מעשה בענבול באחד שנפחתה גלגלתו ועשו לו חידוק של קרויה וחיה אמר ר' שמעון בן אלעזר משם ראיה ימות החמה היה וכיון שעברו עליו ימות הצנה מיד מת.  עכ"ל

It was said of R. Simeon b. Halafta that he was an experimenter in all things.  Indeed he once made an experiment to disprove R. Judah's view.  For we have learnt: "R. Judah says, If its down was gone it is invalid."  Now R. Simeon b. Halafta once had a hen whose down was gone entirely.  He put it into the oven, having first wrapped it in the [warm] leather apron used by bronze workers, and it grew feathers even larger than the original ones.
R. Huna said, The test for a trefah is twelve months.  An objection was raised.  It was taught: The test for a trefah is that it cannot bring forth young.  R. Simeon b. Gamaliel says, If it improves in health it is certainly fit, if it wastes away it is certainly trefah.  Rabbi says, The test for a trefah is thirty days.  But they said to him, Is it not a fact that many continue to live for two or three years? – Tannaim differ in this, for it was taught: If in the skull thre was one long hole or if there were many small holes in it – in either case the hole or holes are computed to make up the emasure of a hole the size of a [surgical] drill.  R. Jose b. ha-Meshullam said, It happened at 'Ain Ibl that a person had a hole in his skull and they put over it a plaster of a gourd-shell and he recovered.  But R. Simeon said to him, Do you mean to prove your case from that?  It happened in the summer months but when winter set in he died.  [translation by Eli Cashdan in The Babylonian Talmud, Rabbi Dr. I. Epstein, ed., Seder Kodashim Vol. III (Hullin I), London: Soncino, 1948]

(Reference from Levi, Facing Current Challenges, Chap. 33, fn. 27)

Chullin 59a-b

Dispute regarding zoology:

חולין נט.-נט: (ש"ס ווילנא); ז"ל

ת"ר אלו הן סימני חיה חיה בכלל בהמה היא לסימנין אמר רבי זירא להתיר חלבה והכי קאמר אלו הן סימני חיה שחלבה מותר כל שיש לה קרנים וטלפים רבי דוסא אומר יש לה קרנים אי אתה צריך לחזור על טלפים יש לה טלפים צריך אתה לחזור על קרנים וקרש אע"פ שאין לו אלא קרן אחת מותר כללא הוא והרי עז דיש לו קרנים וטלפים וחלבו אסור כרוכות בעינן והרי שור דכרוכות וחלבו אסור חרוקות בעינן והרי עז דחרוקות וחלבו אסור מפוצלות בעינן והרי צבי דאין מפוצלות וחלבו מותר חדורות בעינן הלכך היכא דמיפצלא לא דינא ולא דיינא היכא דלא מיפצלא בעינן כרוכות חדורות וחרוקות והוא דמיבלע חירקייהו והיינו ספיקא דעיזא כרכוז. עכ"ל

Our Rabbis taught: The following are the characteristics of wild animals ... But surely the wild animal is included under cattle with regard to the characteristics [of cleanness]! – R. Zera said, [It must be distinguished from cattle] in order that its fat be permitted to be eaten. And it should read thus: The following are the characteristics of wild animals whose fat is permitted: All that have horns and [sharp pointed] hoofs. R. Dosa says, Those that have horns need not be examined as to their hoofs, but those that have [sharp pointed] hoofs must still be examined as to their horns. And the Keresh, though it has but one horn, is permitted. But is this a general rule? Behold the goat has horns and [sharp pointed] hoofs, nevertheless its fat is forbidden! – We mean horns that are rounded. But are not the horns of an ox rounded, yet its fat is forbidden? – We mean horns that are notched. But are not the horns of the goat notched, nevertheless its fat is forbidden? – We mean horns that are forked. But the horns of the deer are not forked, nevertheless its fat is permitted! – We mean horns that are pointed. Therefore, if its horns are forked, there is no question at all about it [i.e., it is certainly a wild animal]. But if they are not forked, we then require them to be rounded and pointed and also notched, and the notches must run one into the other. This indeed is the doubt in connection with the Karkuz goat[: it has all the characteristics of wild animals save that it bears the name 'goat' (Rashi)]. [translation by Eli Cashdan in The Babylonian Talmud, Rabbi Dr. I. Epstein, ed., Seder Kodashim Vol. III (Hullin I), London: Soncino, 1948]

(Reference from Rabbi Chizkiyah da Silva, Pri Chadash, Yoreh De'a 80:2.)

Chullin 63b

The Talmud assumes a Torah scholar might not be able to identify particular species of birds:

חולין סג: (ש"ס ווילנא); ז"ל

א"ר יצחק עוף טהור נאכל במסורת נאמן הצייד לומר עוף זה טהור מסר לי רבי א"ר יוחנן והוא שבקי בהן ובשמותיהן בעי ר' זירא רבו חכם או רבו צייד ת"ש דא"ר יוחנן והוא שבקי בהן ובשמותיהן אי אמרת בשלמא רבו צייד שפיר אלא אי אמרת רבו חכם בשלמא שמייהו גמיר להו אלא אינהו מי ידע להו אלא לאו ש"מ רבו צייד ש"מ: עכ"ל

R. Isaac said, For the eating of clean birds we rely upon tradition. A hunter is believed when he says, ‘My master transmitted to me that this bird is clean’. R. Johanan added, Provided he was familiar with birds and their nomenclature. R. Zera enquired, Does ‘master’ mean a master in learning or in hunting? – Come and hear, for R. Johanan added, ‘Provided he was familiar with birds and their nomenclature’. Now if it means a master in hunting it is well, but if it means a master in learning, I grant you that he would have learnt their nomenclature, but would he actually know them [so as to recognize them]? You must therefore say it means a master in hunting; this is proved.

[translation by Eli Cashdan in The Babylonian Talmud, Rabbi Dr. I. Epstein, ed., Seder Kodashim Vol. III (Hullin I), London: Soncino, 1948]

(Reference from Rabbi Gil Student, “The Approach of the Talmudic Sages to Science,” available at