Airspeed Velocity of an
Unladen Swallow
When Rabbi Jeremiah met his holy grail
Rabbi Neil Janes
bBava Batra 23b
Translation
Notes
A YOUNG PIGEON WHICH IS FOUND
ON THE GROUND WITHIN FIFTY
CUBITS FROM A COTE BELONGS TO
THE OWNER OF THE COTE; IF FOUND
BEYOND FIFTY CUBITS FROM THE
COTE, IT BELONGS TO THE FINDER. IF
IT IS FOUND BETWEEN TWO COTES IT
BELONGS TO THE ONE TO WHOSE
COTE IT IS NEARER. IF IT IS EXACTLY
MIDWAY, THEY MUST SHARE IT.
This is the mishnah that the gemara is going to
interpret. Baba Batra, Chapter 2, deals with
property and the need to ensure that one’s use
of it does not damage another’s property. The
mishnah here is connected to the preceding one,
which included the need for a dovecote to be
situated in a space where there are fifty cubits of
free space on all sides.
‫הבבלי‬
‫ ניפול הנמצא בתוך חמשים‬.'‫תני‬
‫ חוץ‬,‫אמה ־ הרי הוא של בעל השובך‬
‫מחמשים אמה ־ הרי הוא של מוצאֹו‬
‫ קרוב לזה ־‬,‫נמצא בין שני שובכות‬
‫ מחצה על‬,‫ קרוב לזה ־ שלו‬,‫שלו‬
.‫מחצה ־ שניהם יחלוקו‬
Cubits: A cubit is the length from one’s elbow to hand, which is about 50cm.
Diagrams of the cases in the Mishnah:
1)
Case 1: The bird is found
within a 50 cubit radius of
the dovecote.

50
cubits
The bird is returned to the
owner of the dovecote.
Case 2: The bird is found
outside a 50 cubit radius of
the dovecote.
2)
50
cubits

The bird is can be kept by
the finder.
Airspeed Velocity of an Unladen Swallow
Rabbi Neil Janes
The Lyons Learning Project
3)
Case 3: The bird is found
closer to one dovecote
than another.

50
cubits
50
cubits
The bird is returned to the
nearest dovecote.
4)
Case 4: The bird is found
halfway
between
two
dovecotes.

50
cubits
50
cubits
The bird is split between
the two owners of the
dovecotes.
The Talmud continues:
GEMARA. R. Hanina says: If a case can
be decided one way on the ground of
majority and another way on the
ground of nearness, we decide on the
ground of majority. And although the
plea of nearness equally with the plea
of majority derives its warrant from
the Scripture (Exodus 23:2), yet the
plea of majority carries greater
weight.
R. Zera questioned this. Scripture tells
us, “And it shall come to pass that the
city nearest unto the slain man . . .
[shall bring a heifer].” (Deuteronomy
21) that is to say, even though there
are other towns [in the vicinity] with
a larger population? We assume that
there are none. But [if majority is the
decisive factor] why not take the
biggest town anywhere? Scripture
speaks of a town surrounded by
mountains.
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Rabbi Hanina sets up the two halakhic principles
which will be of interest to the gemara. The
principle of ‘nearness’ and of ‘majority’. These are
really measures of probability. Each can be used to
determine, for example, ownership of lost property.
Does it belong to the nearest owner or the owner
with the most number of the lost items. Rabbi
Hanina argues that where the two principles can be
applied the preference is for the plea of the majority,
even though they are both in the Torah.
‫ רוב‬:‫ אמר רבי חנינא‬.'‫גמ‬
Rabbi Zera disagrees with Rabbi Hanina. He argues
this by demonstrating that there is a case in the
Torah which supports his view (from Deuteronomy
21:3). This is the case of a person who is found
murdered in the open and the identity of the
murderer is unknown - the town which is nearest
must make atonement for the murder. According to
Rabbi Zera this implies that the principle of
‘nearness’ is preferred to that of ‘majority’. The
response by the anonymous voice of the gemara is,
“there are none’. There are no towns with a larger
population, hence the case is not one in which a
conflict between nearness and majority is present.
The situation is challenged again, by asking why not
go after the majority found in the world. The reply
given is that the town is isolated. Rashi interprets
this to mean that there is no route for a murderer to
come to the town. Therefore, whereas the case may
have been thought to be one where nearness is
favoured over majority, it is not. Rather it is just a
case of nearness.
)‫ (דברים כ"א‬:‫מתיב רבי זירא‬
2
,‫וקרוב ־ הולכין אחר הרוב‬
‫דאורייתא‬
‫דרובא‬
‫ואע"ג‬
‫ אפילו הכי‬,‫וקורבא דאורייתא‬
.‫רובא עדיף‬
‫והיה העיר הקרובה אל החלל ־‬
‫ואע"ג דאיכא אחריתי דנפישא‬
‫ וליזיל בתר רובא‬.‫מינה בדליכא‬
ִ
.‫דעלמא ביושבת בין ההרים‬
ִ
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Airspeed Velocity of an Unladen Swallow
Rabbi Neil Janes
The Lyons Learning Project
In the Torah: Commandments found in the Torah, described in that way by the sages, are known as de-Oraita. De-Oraita is an
aramaic word which means ‘of the Torah’! Not all commandments are de-Oraita, some are de-Rabbanan - these are
commandments that are ‘of the Rabbis’.
The Principle of Majority: The use of the majority/nearness principles are heuristics for calculating probability. The principle of
majority is preferred in halakha and can be seen at work in the following case: If a town contained a majority of kosher
butchers, let us say 9 out of 10 butchers are kosher, and a piece of meat is found in the street outside the one unkosher butcher,
is the meat considered kosher? The answer is yes; because the majority of butchers are kosher the meat which is found is
assumed to be kosher too.
We learnt: A YOUNG PIGEON WHICH
IS FOUND ON THE GROUND WITHIN
FIFTY CUBITS OF A COTE BELONGS TO
THE OWNER OF THE COTE; and this
even though there may be a bigger
cote in the neighbourhood? We
assume that there is not. If that is so,
then what of the next clause: IF
FOUND BEYOND FIFTY CUBITS FROM
THE COTE, IT BELONGS TO THE
FINDER? Now if there are no other
cotes in the neighbourhood, there
can be no question that the bird
comes from this one? Our Mishnah
speaks [in the first clause] of a bird
which can only hop. Since Mar Ukba
has laid down that a bird which can
only hop does not go further than
fifty cubits.
R. Jeremiah raised the question: If
one foot is within fifty cubits and the
other beyond. How do we decide? It
was for this that they threw R.
Jeremiah out of the Beit Midrash.
The gemara now returns to the mishnah, as
indicated by the words ‘We learnt’ (‫)תנן‬.
Having established that majority is preferred to
a plea of nearness (see above), the mishnah
seems to decide on the basis of nearness.
Therefore the question, “though there may be a
bigger cote in the neighbourhood,” is an ‘attack’
on the previous conclusion that majority is
favoured over nearness.
Once again the
response to the challenge is that there is no
bigger dovecote in the area, hence the ruling on
the basis of nearness is fine.
In response to this answer a new challenge is
levelled. If there are no other dovecotes in the
area then there can be only one owner,
whether within 50 cubits or beyond 50 cubits.
The response to this challenge is to perform a
chiluk, to differentiate between the case at the
beginning of the mishnah, ‘Within 50 cubits’
and the later case, ‘Beyond 50 cubits’. The
‘Within 50 cubits’ case refers to a bird which
can only hop (not fly), and the maximum
distance it can hop (according to Mar Ukba) is
50 cubits. The case of ‘Beyond 50 cubits’
concerns a bird which can fly, hence it follows
after the majority of the world, not the nearest
dovecote.
Finally, Rabbi Jeremiah asks the pivotal
question. If one foot is inside 50 cubits and one
outside 50 cubits how do we decide? (Either
how do we decide who is the owner or how do
we decide what kind of bird it is?)
‫ ניפול הנמצא בתוך חמשים‬:‫תנן‬
‫אמה ־ הרי הוא של בעל השוב ֹך ואף‬
‫מיניה‬
ִ
‫על גב דאיכא אחרינא דנפיש‬
‫ חוץ‬:‫ אימא סיפא‬,‫ אי הכי‬.‫בדליכא‬
‫מחמשים אמה ־ הרי הוא של מוצאֹו‬
‫ ודאי מההוא נפ ִל הכא‬,‫ואי דליכא‬
‫ דאמר רב‬,‫במאי עסקינן ־ במדדה‬
‫ כל המדדה ־ אין‬:‫עוקבא בר חמא‬
.'‫מדדה יותר מנ‬
'‫ רגלו אחת בתוך נ‬:‫בעי ר' ירמיה‬
‫אמה ורגלו אחת חוץ מחמשים‬
‫ מהו? ועל דא אפקוהו לרבי‬,‫אמה‬
.‫ירמיה מבי מדרשא‬
Chiluk: There are a number of techniques used by the sages to resolve challenges to their arguments. A challenge is called a
kushya and a resolution is called a terutz. One way of resolving a kushya is to argue that there are two different scenarios being
talked about - one argument is about oranges and the other about apples. This is a chiluk because it splits the argument and
allows for a resolution to be found.
Beit Midrash: The history and reality of the Beit Midrash in the rabbinic period is not entirely clear. A Beit Midrash means a
House of Study, or perhaps House of Inquiry.
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Airspeed Velocity of an Unladen Swallow
Rabbi Neil Janes
The Lyons Learning Project
The isolated dovecote and the Talmudic chiluk:
The Talmud describes a completely isolated dovecote, so that there is only one dovecote from which a bird within 50 cubits
could come. Therefore, the bird must be returned to the owner of the dovecote:

50
cubits
However, if the dovecote is isolated, why should we not return a bird found beyond 50 cubits to the owner of the dovecote,
rather than let the finder keep it?

50
cubits
The answer is, according to the Talmud, that they are two different birds: In the first case, the bird is a young chick, only able to
walk, and could not hop further than the 50 cubits. On the other hand a bird beyond 50 cubits is a bird that can fly and could
have come from far away.
50
cubits
50
cubits
Rabbi Jeremiah wants to know: What if one foot was beyond the 50 cubit distance from the dovecote
and one foot within? Who gets to keep the bird and what kind of bird is it anyway? For this, he is thrown
out of the study hall.
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Airspeed Velocity of an Unladen Swallow
Rabbi Neil Janes
The Lyons Learning Project
Sages in the text:
There are two general periods in rabbinic literature, they have an internal consistency to the text. The first is the Tannaitic
period: the tannaim are the sages of the mishnaic period (approx. 0-200CE). The second period is the Amoraic period: the
amoraim are the sages of the Talmud (approx. 200-500CE).
Rabbi Hanina: Is an early Amora (first generation of Amoraim) who was a student of Rabbi Judah Ha-Nasi and taught in
Sepphoris. He studied in Babylonia and then came to Palestine.
Rabbi Zera: There are two Rabbi Zeras, but this is most likely the older of the two, who was the teacher of Rabbi Jeremiah. He
is about two generations after Rabbi Hanina. Also came from Babylonia to Palestine.
Mar Ukba: Again there were two Mar Ukbas! Both were exilarchs (head of the exiled community in Babylonia).
Rabbi Jeremiah: Originally came from Babylonia and was a student of Rabbi Zera. He became the authority of the community
in Tiberias.
What was the problem with Rabbi Jeremiah?
(according to medieval commentaries)
Rashi (11th Century)
.‫ שהיה מטריח עליהם‬- ‫ועל דא אפקוהו‬
“For this they threw him out” - because he was wearisome for them.
Tosafot (commentaries after Rashi including Rashi’s grandson)
‫ אין לפרש משום דבעי מילתא דלא שכיחא כלל דהיכי איתרמי דרגלו אחת תוך חמשים ורגלו‬.‫על דא אפקוהו לרבי ירמיה מבי מדרשא‬
‫אחת חוץ לחמשים בצמצום דהא אשכחנא דמתניתין נמי בכהאי גוונא איירי דקתני מחצה על מחצה יחלוקו ונראה לרבינו תם דמשום‬
:‫הכי אפקוהו משום דמדדה אינו מדדה כלל יותר מחמשים אמה אפילו רגלו אחת דכל מדות חכמים כן הוא‬
“For this they threw R. Jeremiah out of the Beit Midrash” - This cannot be explained because his question is about a case that
does not generally happen. For how could it happen that one foot was within fifty cubits and one foot outside fifty cubits? With
a narrowing of the case, for we have also found this in our mishnah according to the example dealing with, “if half and half, they
split it.” For Rabbenu Tam it seems that they threw him out because a ‘hopping bird’ is not able to hop more than fifty cubits not even one foot. For all the measurements of the sages are so.
Hyam Maccoby - from ‘The Day God Laughed’
Maccoby quotes the following: ‘Rabbi Aha ben Jacob said: Rabbi Zera never laughed in his life, and even Rabbi Jeremiah failed to
make him laugh.’ (B. Niddah 23a)
“The great scholar Isaac Halevi in his Dorot Harishonim tried to argue that all Rabbi Jeremiah’s questions were meant seriously,
being intended to attack the Sages’ methods of fixing limits and measures. Significantly, however, Halevi makes no reference to
the last-given instance above, or to the comment of Rabbi Aha ben Jacob...
The trouble with Rabbi Jeremiah was that he was an ultra-rationalist, who could not bring himself to accept the element of
arbitrariness in human affairs. His teacher, Rabbi Zera, tried to reconcile him to the fact that rules have to be precise, even
though no reason can be given why the line is drawn precisely at this point.
Rabbi Jeremiah was eventually accepted back in the House of Study, and, in time became a great authority.
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Airspeed Velocity of an Unladen Swallow
Rabbi Neil Janes
The Lyons Learning Project
Alan Dershowitz - from ‘The Genesis of Justice’
Pages 4-5
If a skeptical student asked a question outside of the canon, the teacher had a ready response: “If your question were a good
one, the rabbis before you, who were so much smarter than you, would have asked it already. If they did not think of it, then it
cannot be a good question.” The teachers even had an authoritative source for their pedagogical one-upmanship. The Talmud
recounts the story of the great teacher Rabbi Eliezer, who was teaching the following principle:
If a fledging bird is found within fifty cubits [about seventy-five feet] … [of a man's property], it belongs to the owner of
the property. If it is found outside the limits of fifty cubits, it belongs to the person who finds it.
Rabbi Jeremiah asked the question: “If one foot of the fledging bird is within the limit of fifty cubits, and one foot is
outside it, what is the law?”
It was for this question that Rabbi Jeremiah was thrown out of the house of study.
I would occasionally ask impertinent questions that got me tossed out of class. I remember upsetting a teacher by asking where
Cain's wife came from, since Adam and Eve had no daughters. A classmate was slapped for wondering how night and day existed
before God created the sun and the moon. My teachers dubbed these questions klutz kashas-the questions of a “klutz,” or
ignoramus. But I persisted in asking them, as did many of my classmates. I continue to ask them in this book.
Re-reading the text:




An interesting question to ask ourselves is why, on this discussion in particular, does the text tell us that Rabbi Jeremiah
was thrown out of the Beit Midrash?
Couldn’t it be that there were other occasions when Rabbi Jeremiah was more irksome?
After all, as Tosafot point out, the case that Rabbi Jeremiah describes is almost identical to one already found in the
mishnah - so why throw him out now?
The argument of Rabbi Jeremiah is one of reductio ad absurdum - he takes the arguments of the text, which already
seem a little absurd, to the end point - thus demonstrating the inherent problem. What’s so bad about that?
Perhaps if we read the text as a literary work it might make additional sense...
1 Rabbi Jeremiah’s question is about a bird which is straddling a boundary; a boundary which, within the world of the sages, is
not arbitrary but determinative of two different birds.
2 Rabbi Jeremiah is, on the one hand, arguing his case from within the world view of the sages- using their own methods against
them. On the other hand he is challenging the world view of the sages by trying to demonstrate the fallacy of their
measurements. In effect, Rabbi Jeremiah straddles the boundary between the sages’ world view and that of the ‘outside’
world.
3 From the sages’ perspective, the bird must be either a ‘hopping bird’ or a bird that flies. As the Ritba points out - if it has one
leg over the fifty cubits then it cannot be a hopping bird. Similarly, from the sages’ perspective, a person can either accept
their world view or not. You cannot straddle one foot in and one foot out.
4 Consequently, just as the bird must be one or the other, so too Rabbi Jeremiah must either be in or out. Since he has a foot
over the line he must be fully out - and that is why they throw him out.
Monty Python’s ‘Holy Grail’ (further proof they were influenced by the Talmud!)
Bridgekeeper: What... is the air-speed velocity of an unladen swallow?
King Arthur: What do you mean? An African or European swallow?
Bridgekeeper: Huh? I... I don't know that.
[he is thrown over]
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