Noah is an ambiguous hero. The very first verse of our parsha hints at this ambiguity. He was “blameless in his age,” we are told. Rashi, quoting the midrash, picks up the qualification: In his age, Noah was considered blameless, but had he lived in Abraham’s time, he would never have been viewed as blameless.

True, the concluding words of last week’s parsha tells us that Noah “found favor with the Lord.” And true, when God commands Noah to enter the ark, God notes, “For you alone have I found righteous before me in this generation.” But again, note the qualification: “in this generation”; but what about in other generations?

So Noah saves himself and his family, but at no point does he intercede on behalf of the rest of creation. The comparison with Abraham’s intercession on behalf of Sodom and Gomorra cries out for attention.

What does Noah do after exiting from the ark? He plants a vineyard, drinks the wine, becomes drunk, and exposes himself in his tent. Again Rashi quotes the midrashic play on the Hebrew word indicating that “he was the first” (to plant a vineyard). The biblical text reads “vayahel,” but the midrash reads it: “he became hulin,” literally, he profaned himself. Rashi asks, Could he not have chosen something else to plant?

If Noah is an ambiguous hero, then this quality captures God’s own ambivalence about all of creation. The text traces the ups and downs of God’s feelings about creation in fine detail.

At the climax of the first creation story, God gazes upon the whole of creation and finds it “very good.” But then follow the Eden story, Cain and Abel, and the mysterious reference to the Nephilim. Whatever that was about, it clearly was nothing positive, because we are told that God saw man’s wickedness and that all human plans were nothing but evil all the time. “And the Lord regretted that He had made man on earth and His heart was saddened.” God determines to blot out all of creation except for Noah, who “found favor with the Lord.”

Within 10 generations, the world that God found to be “very good” at the outset is now to be exterminated. “Exterminate” is not too strong a term here. God uses the same Hebrew word to refer to the extermination of Amalek, Israel’s archenemy. But in the very same breath, we are told that Noah found favor in God’s eyes. The midrashic uncertainty about Noah’s qualities is quite understandable: In a generation worthy of extermination, of course Noah was a righteous man.

After the flood, God reconsiders still again. God “smelled the pleasing odor of Noah’s sacrifices” — one of the Torah’s more striking anthropomorphisms — and determines never again to destroy creation: “Never again will I doom the earth because of man,” but this time, it’s for a far different reason. This time, it’s because God has finally come to terms with reality. It’s because “the devisings of man’s mind are evil from his youth.”

Ten generations after Noah, with the emergence of Abraham, everything changes — both God and humanity. With Abraham, there is no more ambiguity, and with God there is no more ambivalence. That transformation is signaled by Abraham’s momentous debate with God over the fate of Sodom and Gomorra. Now, both God and Abraham share a commitment to doing what is just and right. God can no longer simply destroy civilization at will. Now Abraham must approve. Now, indeed, everything has changed.