Brachot 3a: Three watches -- Go and look!

On Berachot 3a, we see the following curious gemara:

• עד סוף האשמורה: מאי קסבר רבי אליעזר? אי קסבר שלוש משמרות הוי הלילה, לימא "עד ארבע שעות"; ואי קסבר ארבע משמרות הוי הלילה, לימא "עד שלוש שעות"!

לעולם קסבר שלוש משמרות הוי הלילה; והא קא משמע לן, דאיכא משמרות ברקיע, ואיכא משמרות בארעא.

דתניא, רבי אליעזר אומר: שלוש משמרות הוי הלילה, ועל כל משמר ומשמר יושב הקדוש ברוך הוא ושואג כארי, שנאמר: "ה' ממרום ישאג וממעון קדשו יתן קולו, שאוג ישאג על נוהו". וסימן לדבר – משמרה ראשונה, חמור נוער; שניה, כלבים צועקים; שלישית, תינוק יונק משדי אמו ואשה מספרת עם בעלה.

מאי קא חשיב רבי אליעזר? אי תחילת משמרות קא חשיב – תחילת משמרה ראשונה, סימנא למה לי? אורתא הוא! אי סוף משמרות קא חשיב – סוף משמרה אחרונה, למה לי סימנא? יממא הוא!

אלא חשיב סוף משמרה ראשונה, ותחילת משמרה אחרונה, ואמצעית דאמצעיתא.

ואיבעית אימא, כולהו סוף משמרות קא חשיב. וכי תימא, אחרונה לא צריך? למאי נפקא מינה? למיקרי קריאת שמע, למאן דגני בבית אפל ולא ידע זמן קריאת שמע אימת; כיון דאשה מספרת עם בעלה ותינוק יונק משדי אמו, ליקום וליקרי.

Or, in English:

UNTIL THE END OF THE FIRST WATCH. What opinion does R. Eliezer hold? If he holds that the night has three watches, let him say: Till four hours [in the night]. And if he holds that the night has four watches, let him say: Till three hours? — He holds indeed, that the night has three watches, but he wants to teach us that there are watches in heaven⁸  as well as on earth. 

For it has been taught: R. Eliezer says: The night has three watches, and at each watch the Holy One, blessed be He, sits and roars like a lion. For it is written: The Lord does roar from on high, and raise His voice from His holy habitation; 'roaring He doth roar'⁹  because of his fold. And the sign of the thing is:¹⁰  In the first watch, the ass brays; in the second, the dogs bark; in the third, the child sucks from the breast of his mother, and the woman talks with her husband. 

What does R. Eliezer understand [by the word watch]? Does he mean the beginning of the watches? The beginning of the first watch needs no sign, it is the twilight! Does he mean the end of the watches? The end of the last watch needs no sign, it is the dawn of the day! He, therefore, must think of the end of the first watch, of the beginning of the last watch, and of the midst of the middle watch. 

If you like I can say: He refers to the end of all the watches. And if you object that the last watch needs no sign, [I reply] that it may be of use for the recital of the Shema', and for a man who sleeps in a dark room¹¹  and does not know when the time of the recital arrives. When the woman talks with her husband and the child sucks from the breast of the mother, let him rise and recite.

What I find curious about this is that these times are meant to be practical. That means that regularly, when the woman talks with her husband and the child sucks from the breast of the mother, it is the time. And so even if he sleeps in a dark room, he will know what time it is.

If so, how can there be any doubt as to whether Rabbi Eliezer means the beginning or end of the watches, such that the gemara gives two possibilities, with an איבעית אימא connecting them? Rather than the gemara wondering whether it is X or Y, let the Savora (or Amora) who wonders this simply check it out. When the woman talks with her husband or the baby suckles, let him be in a non-dark room, and see whether it is dawn or not. This is not something to be left to sevara, and indeed left unresolved.

And if it is not possible to resolve it trivially in this manner, then again, Rabbi Eliezer's signs are useless.

To my mind, the answer is simply that this was not necessarily Rabbi Eliezer's intent. This anonymous Aramaic systematic analysis, with an איבעית אימא, is clearly a post-Amoraic setama de-gemara.

What did Rabbi Eliezer mean in the brayta:

R. Eliezer says: The night has three watches, and at each watch the Holy One, blessed be He, sits and roars like a lion. For it is written: The Lord does roar from on high, and raise His voice from His holy habitation; 'roaring He doth roar'⁹  because of his fold. And the sign of the thing is:¹⁰  In the first watch, the ass brays; in the second, the dogs bark; in the third, the child sucks from the breast of his mother, and the woman talks with her husband.

The purpose of these signs is not necessarily practical at all. Rather, the point is to demonstrate that that are physical manifestations on Earth of Hashem's roaring On High (in sadness at the destruction of the Temple and the Exile). The donkey is sensing something; as do the dogs; as does the infant, or the woman, who stirs at these times.

If so, it does not matter that one mishmar is at twilight or at dawn. The point is the physical reaction in the world to Hashem's roaring, not for the sake of identifying the mishmar. (For why should one need to know these mishmarot, if the idea of yerei shamayim arising at mishmarot is post-Talmudic?)

Indeed, if the Radak is correct and there is a connection between the pasuk about Hashem roaring: {Yirmeyahu 25:30}:

ל  וְאַתָּה תִּנָּבֵא אֲלֵיהֶם, אֵת כָּל-הַדְּבָרִים הָאֵלֶּה; וְאָמַרְתָּ אֲלֵיהֶם, ה' מִמָּרוֹם יִשְׁאָג וּמִמְּעוֹן קָדְשׁוֹ יִתֵּן קוֹלוֹ--שָׁאֹג יִשְׁאַג עַל-נָוֵהוּ, הֵידָד כְּדֹרְכִים יַעֲנֶה אֶל כָּל-יֹשְׁבֵי הָאָרֶץ.

30 Therefore prophesy thou against them all these words, and say unto them: The LORD doth roar from on high, and utter His voice from His holy habitation; He doth mightily roar because of His fold; He giveth a shout, as they that tread the grapes, against all the inhabitants of the earth.

and the pasuk in {Eicha 2:19}:

יט  קוּמִי רֹנִּי בליל (בַלַּיְלָה), לְרֹאשׁ אַשְׁמֻרוֹת--שִׁפְכִי כַמַּיִם לִבֵּךְ, נֹכַח פְּנֵי אֲדֹנָי; שְׂאִי אֵלָיו כַּפַּיִךְ, עַל-נֶפֶשׁ עוֹלָלַיִךְ--הָעֲטוּפִים בְּרָעָב, בְּרֹאשׁ כָּל-חוּצוֹת.  {ס}

19 Arise, cry out in the night, at the beginning of the watches; pour out thy heart like water before the face of the Lord; lift up thy hands toward Him for the life of thy young children, that faint for hunger at the head of every street.' {S}

then it should be specifically at the beginning of each mishmar. Unless one separates the signs of the mishmarot from the warnings.

Another difficulty with the setama degemara's reinterpretation of Rabbi Eliezer is that the middle of a mishmar is not very useful as a sign of the mishmar. And one would have really expected a consistency in how to describe the signs of mishmarot, rather than the inconsistent hodgepodge that is presented.

Finally, looking to science contemporary to Chazal, we have the following from A Source Book in Medieval Science, by Edward Grant:

Physiologus lived between the 2nd and 5th century CE, and he refers to an instance of a donkey braying regularly through the night, such that one can tell each hour, the time. Note the parallel to our gemara, where a donkey's braying marks a mishmar. It is not impossible that some ancient scientist has made some parallel statement about mishmarot breaking up the night. If so, we might be able to get

So too, there is an ancient association between night-watches and a child waking. To cite The Babylonian Gilgamesh Epic: Introduction, Critical Edition...,

The dispute as to whether the night has three or four watches seems to be a matter of dispute between the Babylonians (who say three) and the Egyptians and Romans (who say four). Different Tannaim took different sides, ran with it.