History's staged ascent toward unity for Heaven's sake

בענין דור המבול והפלגה שהי' הדורות הולכין ומתוקנים מדריגה אחר מדריגה כחשבון המשניות דאבות עשרה דורות מאדם עד נח להודיע כו' שהיו מכעיסין עד שהביא עליהם המבול והם נאבדו לגמרי שהי' רק רע כל היום.

Concerning the generation of the Flood and the generation of the Dispersion — that the generations were progressing and being rectified, level after level, in line with the count of the Mishnayos in Avos: "ten generations from Adam to Noach," to make known… that they kept provoking until He brought the Flood upon them, and they were utterly destroyed, for they were "only evil all the day."

The Sefas Emes reads human history as a gradual refinement, level by level, paralleling the Mishnah in Avos. The dor ha-mabul reached the point of being "only evil all day long," and so was completely wiped out by the Flood.

ואח"כ בדור הפלגה הי' להם האחדות כמ"ש שפה אחת כו' רק שלא הי' כנסי' לש"ש ולא נתקיים.

And afterward, in the generation of the Dispersion, they had achdus (unity), as it says, "one language…", only that it was not a gathering for the sake of Heaven, and so it did not endure.

The next stage, the dor ha-flagah, represents an advance: they attained unity. But their unity was directed against Hashem rather than l'shem Shomayim, so it could not last.

ואמרו שבא אברהם אבינו וקיבל שכר כולן ולא נאבדו לגמרי כדור המבול.

And Chazal said that Avraham Avinu came and received the reward of all of them — and they were not utterly destroyed as the generation of the Flood was.

Because the generation of Dispersion had at least achieved unity, it contained a redeemable element; Avraham emerged from it and "collected the reward of them all," so they were not annihilated like the Flood generation.

וחח"כ עשרה נסיונות עשרה נסים שזכו אח"כ בנ"י להעלות ההנהגה להשי"ת שזה הוראת הניסים.

And afterward [came] the ten nisyonos (trials) and the ten nissim (miracles), through which Bnei Yisrael subsequently merited to raise the conduct of the world up to Hashem — for this is what the miracles signify.

The next rungs are Avraham's ten tests and the ten miracles in Mitzrayim; through them Bnei Yisrael lifted the world's natural order back up to Hashem, which is the very meaning of a neis — nature openly subordinated to its Source.

וכ"ז צריך להיות כך הסדר גם בכל פרט האדם שמקודם יש תהו ובהו וצריכין יגיעה לבוא לבחי' האחדות אח"כ צריכין לייגע שיהי' האחדות לשם שמים:

And all of this order must likewise be so within each individual person: at first there is "tohu va-vohu (chaos and void)," and one must toil to arrive at the aspect of achdus; afterward one must toil so that the achdus be for the sake of Heaven.

The same staged progression recurs in every person's avodah: one begins in inner chaos, labors to reach an integrated unity within oneself, and then must labor further so that this unity be wholly l'shem Shomayim — the lesson of where the dor ha-flagah fell short.

Summary: Human history advances level by level — the Flood generation, "only evil," was destroyed; the Dispersion generation achieved unity but not "for the sake of Heaven," so it failed to endure, yet was not annihilated since Avraham arose from it to collect their reward. Through the ten trials and ten miracles, Bnei Yisrael lifted the world's order back to Hashem. This same sequence repeats in each person: from inner chaos, to toiling for unity, to ensuring that unity is l'shem Shomayim.