Vayera: The Motivation of Lot's Daughters

Did they sleep with their father to preserve the human race? Or did they do it to preserve their family line? Or just because no other men were available?

The pesukim state the following, but of course a text can be interpreted in any number of ways:

ל וַיַּעַל לוֹט מִצּוֹעַר וַיֵּשֶׁב בָּהָר, וּשְׁתֵּי בְנֹתָיו עִמּוֹ, כִּי יָרֵא, לָשֶׁבֶת בְּצוֹעַר; וַיֵּשֶׁב, בַּמְּעָרָה--הוּא, וּשְׁתֵּי בְנֹתָיו.	30 And Lot went up out of Zoar, and dwelt in the mountain, and his two daughters with him; for he feared to dwell in Zoar; and he dwelt in a cave, he and his two daughters.
לא וַתֹּאמֶר הַבְּכִירָה אֶל-הַצְּעִירָה, אָבִינוּ זָקֵן; וְאִישׁ אֵין בָּאָרֶץ לָבוֹא עָלֵינוּ, כְּדֶרֶךְ כָּל-הָאָרֶץ.	31 And the first-born said unto the younger: 'Our father is old, and there is not a man in the earth to come in unto us after the manner of all the earth.
לב לְכָה נַשְׁקֶה אֶת-אָבִינוּ יַיִן, וְנִשְׁכְּבָה עִמּוֹ; וּנְחַיֶּה מֵאָבִינוּ, זָרַע.	32 Come, let us make our father drink wine, and we will lie with him, that we may preserve seed of our father.'
לג וַתַּשְׁקֶיןָ אֶת-אֲבִיהֶן יַיִן, בַּלַּיְלָה הוּא; וַתָּבֹא הַבְּכִירָה וַתִּשְׁכַּב אֶת-אָבִיהָ, וְלֹא-יָדַע בְּשִׁכְבָהּ וּבְקוּמָהּ.	33 And they made their father drink wine that night. And the first-born went in, and lay with her father; and he knew not when she lay down, nor when she arose.
לד וַיְהִי, מִמָּחֳרָת, וַתֹּאמֶר הַבְּכִירָה אֶל-הַצְּעִירָה, הֵן-שָׁכַבְתִּי אֶמֶשׁ אֶת-אָבִי; נַשְׁקֶנּוּ יַיִן גַּם-הַלַּיְלָה, וּבֹאִי שִׁכְבִי עִמּוֹ, וּנְחַיֶּה מֵאָבִינוּ, זָרַע.	34 And it came to pass on the morrow, that the first-born said unto the younger: 'Behold, I lay yesternight with my father. Let us make him drink wine this night also; and go thou in, and lie with him, that we may preserve seed of our father.'
לה וַתַּשְׁקֶיןָ גַּם בַּלַּיְלָה הַהוּא, אֶת-אֲבִיהֶן--יָיִן; וַתָּקָם הַצְּעִירָה וַתִּשְׁכַּב עִמּוֹ, וְלֹא-יָדַע בְּשִׁכְבָהּ וּבְקֻמָהּ.	35 And they made their father drink wine that night also. And the younger arose, and lay with him; and he knew not when she lay down, nor when she arose.
לו וַתַּהֲרֶיןָ שְׁתֵּי בְנוֹת-לוֹט, מֵאֲבִיהֶן.	36 Thus were both the daughters of Lot with child by their father.
לז וַתֵּלֶד הַבְּכִירָה בֵּן, וַתִּקְרָא שְׁמוֹ מוֹאָב: הוּא אֲבִי-מוֹאָב, עַד-הַיּוֹם.	37 And the first-born bore a son, and called his name Moab--the same is the father of the Moabites unto this day.
לח וְהַצְּעִירָה גַם-הִוא יָלְדָה בֵּן, וַתִּקְרָא שְׁמוֹ בֶּן-עַמִּי: הוּא אֲבִי בְנֵי-עַמּוֹן, עַד-הַיּוֹם. {ס}	38 And the younger, she also bore a son, and called his name Ben-ammi--the same is the father of the children of Ammon unto this day. {S}

Now, they left the city of Tzoar, and it was fine, so we should expect that they would know there are other people around. Yet their statement וְאִישׁ אֵין בָּאָרֶץ לָבוֹא עָלֵינוּ, "there is not a man in the earth to come in unto us," would imply that there are no men present, perhaps no men present on earth!

Rashi explains:

and there is no man on earth They thought that the entire world had been destroyed, as in the Generation of the Flood (Gen. Rabbah 51:8).

Thus, just as the duty after the flood was to repopulate the earth, so too the daughters of Lot thought to repopulate the earth. The only available male was their father, and thus they were acting properly.

Indeed, Chazal point to the pasuk in Tehillim 89:3:

ג כִּי-אָמַרְתִּי--עוֹלָם, חֶסֶד יִבָּנֶה; שָׁמַיִם, תָּכִן אֱמוּנָתְךָ בָהֶם.

3 For I have said: 'For ever is mercy built; in the very heavens Thou dost establish Thy faithfulness.

And note that chessed on occasion refers to incest, and thus this was permitted for the purpose of building the world, for Kayin, Hevel, and Shet, who perforce married their sisters.

The same would apply to the daughters of Lot. Except of course that they were mistaken.

Suggestions have been made such as that perhaps the angel only held off destroying Tzoar while they were present, but once they left, they thought that city might be destroyed as well.

I would note that such a fear finds purchase within the text, for it states that they feared to stay in Tzoar, and this was the motivation for withdrawing to a cave.

Many commentators follow in this path, that they mistakenly thought they were the last surviving humans.

One exception is Sforno, who says that they knew that others were present, but the custom of the place was to take a woman who was fit for him, and for some reason the men were unfit for them, or they for the men.

It seems to me that he is partly basing this on וְאִישׁ אֵין בָּאָרֶץ לָבוֹא עָלֵינוּ כְּדֶרֶךְ כָּל-הָאָרֶץ, and specifically כְּדֶרֶךְ כָּל-הָאָרֶץ. What does this phrase, "after the manner of all the earth," mean? Perhaps the way of the earth is to procreate. Or perhaps "the manner of all the earth" means non-incestuous relations, and since the normal derech eretz is not present, they must resort to the otherwise inconceivable.

But I would suggest that he reads כְּדֶרֶךְ כָּל-הָאָרֶץ, "after the manner of all the earth," as because of the custom of all the land, and that custom must have been to only marry a woman who is fit for him and vice versa. Indeed, Targum Yerushalmi renders it as something like ke-nimus kol `ar'a`, like the law of the land, either referring to the ban on incestuous relations or else something like Seforno proposes here.

Shadal bases himself mainly on Seforno here, considering it peshat, although he makes a few tweaks:

אבינו זקן : ולא יתאמץ להרחיק נדוד אל ארץ אחרת ( ספורנו ) ולא יתעורר להשיאנו לאיש. ואיש אין בארץ : לא בכל העולם, אלא בגליל זה ( ספורנו ), והנה שם בהר היה יישוב ומשם היה להם לחם ויין, אמנם לוט לסיבה מן הסיבות לא היה חפץ בחברתם (אולי מפני שראה כי התחברותו עם אנשי סדום גרם לו רעה וסכנה), ועל כן ישב במערה ואמר לבנותיו כי אין אנשי הגליל ההוא ראויים להתחבר אליהם, זה טעם ואיש אין בארץ (ראוי והגון) לבוא עלינו כפירוש ספורנו

Thus, he explains וְאִישׁ אֵין בָּאָרֶץ, as referring to the particular place, but not that there is no man in the entire world. That is, he rejects the midrash that the daughters thought the entire world was destroyed, and says that of course they knew of other humans. But that Lot, after this bad experience with joining in marriage with the Sodomites, was wary of marrying his daughters to others in the region. (I would note that one should see Avraham and Yitzchak's similar take on the matter.) That is why he cut himself off from civilization and told his daughters that the men in the area were not fit to join with. He reads וְאִישׁ אֵין בָּאָרֶץ as there being no fit man to join in marriage with.

Shadal also notes an interesting proof. They had to get food {lechem} to eat while in the cave. And they had wine. The wine must have come from somewhere! Thus, there was a settlement on the mountain, and they got their bread and wine from there.

Rashi also addresses the issue, noting the strangeness of wine being available to them:

And they gave, etc., to drink Wine was made available to them in the cave to make it possible for two nations to emerge from them. — [from Sifrei Ekev 43]

I would point out that this could have been early on, and they could have brought this wine with them from Tzoar.