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The Approach of the Talmudic Sages to Science

There are many areas of halacha that require a knowledge of science. The question we are addressing is how the sages of the Talmud acquired their knowledge. Did they sit in a classroom and theorize about reality? Did they rely on their deductions from the Bible?

Today, we know that leading halachic scholars are in frequent contact with scientific experts. Rabbis like R' Shlomo Zalman Auerbach zt"l and R' Moshe Feinstein zt"l consulted often with doctors and engineers. They knew the halacha. However, they had to consult with scientific experts to determine how to apply halacha. There are even institutes, like Tzomet, that specifically study science in order to better understand its halachic implications. But this is not new. Rabbis have been consulting with scientific experts for centuries. For example, in the 1700s there was a debate regarding the permissibility of a chicken with no visible heart. After R' Tzvi Ashkenazi, the Chacham Tzvi, appealed to medicine to prove his point, R' Yonatan Eybeshutz consulted with university professors (see Chacham Tzvi 74-78; Kreiti Upleiti 40:4).

What we will see is that the sages were similarly concernced with scientific reality. They conducted experiments and consulted with experts to determine how halacha should be applied.


In Chullin 45b we find Rav Dimi bar Yitzchak asking Rav Yehuda how far an animal's spinal cord extends because it has repercussions on whether an animal is a treifa. Rav Yehuda did not just describe what it looks like. He took a lamb and tried to show it to him. Only after two lambs were inadequate for the demonstration (one was too fat and one was too skinny) did Rav Yehuda explain it orally without a demonstration. These were not merely two rabbis sitting in a classroom discussing the anatomy of an animal. They actually dissected animals to observe their anatomy.

Similarly, when the students of R' Yishmael wanted to know how many bones are in a person, in order to determine what constitutes a majority of a skeleton and therefore renders others impure, they took the remains of a woman burned to death by the government and counted her bones (Bechorot 45a).

When R' Shimon ben Chalafta wanted to dispute R' Yehuda's ruling that a bird whose feathers were removed while alive is not kosher, he performed an experiment to demonstrate his point. He removed the feathers from a bird and then kept it warm until it grew even more feathers than it originally had (Chullin 57b). That experiment proved that the removal of feathers could not be a fatal wound and render an animal a treifa.

In Avodah Zara 28a, we are told that Mar bar Rav Ashi was afflicted with tzafdina - scurvy of the gums. He consulted with various experts and received many different suggestions of how to cure his sickness. One by one he tried them and determined which cure worked. On medical advice, he tried applying leaven-water with olive oil and salt to his gums but that did not work. He sought out further advice and smeared goose fat on his gums with a goose quill, but that did not work. After all of the expert suggestions failed to cure his disease, he heard from a certain Arab that he would be healed if he got seeds of an olive that were not yet one third ripe, burned them on a new spade, and spread the ashes on his gums. When he tried this, it worked.

This was a primitive example of a scientific method. He did not simply pray for his disease to go away (although he certainly prayed in addition to his efforts) or try to deduce cures from biblical verses. He consulted with medical experts and followed their advice, noting which cures failed and which one finally worked. This was not as thorough as a modern medical study. There were no blind tests and repeated experiments to verify results. But this should not be expected, as "the scientific method" had not yet been invented. Rather, this was a common-sense approach to finding a cure for a disease. He tried every remedy available until one worked.

In Sanhedrin 5b, Rav tells us that he spent 18 months living with a cattle breeder in order to understand which animal defects are temporary and which are permanent. All this tells us that the sages were very interested in the reality of nature and took great pains to understand it.

Consulting With Experts

But certainly rabbis who spent all their time studying and teaching could not become experts in every field. That is why they also consulted with experts.For example, in Chullin 63b we find that hunters and trappers are used as reliable experts in identifying kosher birds. In Chullin 77a, we find doctors advising the sages on surgical techniques.

Rav Ashi said: When we were at the school of Rav Papi he asked us, "What if the flesh around a fracture was cut away in a circle like a ring?" I answered from what Rav Yehuda said in the name of Rav, "I asked this of wise men and doctors and they said that one should make incisions around the edges of the flesh with a bone and it will heal up, but not with an iron instrument because it will cause inflamation."

In Avoda Zara 28a we are told that R' Yochanan was afflicted with scurvy of the gums, like Mar bar Rav Ashi above. He extracted the medical explanation from a wise Gentile woman and taught it to his students. Clearly, they were willing to accept science from Non-Jewish sources.

Similarly in Niddah 22b we are told by R' Elazar ben Tzadok that a woman was having miscarriages that looked like red membranes. They checked with doctors who gave her medical advice.

In Sanhedrin 33a we meet Todos the famous doctor whose medical advice was highly prized by the sages of the Talmud. "When the matter was brought before the sages of Yavneh, they permitted it as Todos the doctor said, 'No cow or pig leaves Alexandria in Egypt unless its womb is removed so it cannot give birth.'" While in this case, Todos' knowledge of the contemporary medical practices was used, his medical opinion was also used. The following event is recorded in Nazir 52a.

R' Yehuda says: Six things were declared impure by R' Akiva and pure by the Sages, and R' Akiva retracted his opinion. It happened that a basket full of human bones was taken into the synagogue of Tarsi'im and placed in the open air. Then Todos the doctor together with all the doctors entered and said that there was not a backbone of a single corpse there.

The rabbis of the Talmud were very much aware that they needed to consult with scientific experts. However, even this expert advice seems odd from the modern perspective. That is not because the sages did not do their best to utilize the most advanced medicine. It is because medicine has changed dramatically since that time. Imagine what historians in two thousand years will think of our "advanced" science. However, we are still have to do our best and seek out the best scientific knowledge available. The sages in their day were no more ignorant than lehavdil the Greek scientists and philosophers who are held in such high esteem in the Western world.

Contributor(s): Gil Student
Last revised: 10/31/01
© Aishdas 2001