Before the Flood, God judged humanity's wickedness to be total: "every intent of the thoughts of his heart was only evil continually" (Genesis 6:5). This stands in deliberate contrast to Genesis 1:31, where all He had made was "very good." In about sixteen centuries, mankind went from very good to rotten to the core, because sin separates people from God (Isaiah 59:1-2), as Adam and Eve's expulsion from Eden illustrated. God's phrasing shows how complete the corruption was. He saw it, meaning He closely scrutinized a steady decline across many centuries, with only a few bright spots such as Abel, Enoch, and Noah. The wickedness was great, truly evil rather than merely naughty, and the Hebrew word implies it multiplied, almost exponentially, until repentance became ever less likely. It was "in the earth," so it was global, and God's just answer to universal sin was a universal Flood. The second clause intensifies the first. "Intent" is the attitudinal germ behind thoughts, words, and actions, so outward violence flowed from inward corruption, and everything people touched they turned to sin and destruction. Their hearts were "only" evil, with no good mixed in, not even good motives for evil deeds. The evil was also "continually," all the day, without pause. Every person's every thought was altogether evil all the time.

Human wickedness is total and permanent. In Genesis 6:5 God declared mankind altogether evil, from innermost intentions to public behavior, and sent the Flood to destroy the sinners. Yet after the Flood, in Genesis 8:21, He restates nearly the same verdict: the imagination of man's heart is evil from his youth. The Flood changed nothing about human character; it only executed judgment and gave eight people a chance to do better. The phrase "from his youth" allows only a narrow window of potential goodness in early childhood. Babies are born morally neutral, able to do good or evil, but because of the flesh they lean toward selfishness and sin, since carnal nature wants everything for itself. Humanity has not improved since Noah's day, whatever evolutionists argue. Scripture, the story of God's redemption of mankind, shows this throughout. David describes mankind's corruption in Psalm 14:1-3, and God's words in Isaiah portray a people so sinful that renewed efforts to turn them back would only meet rebellion. Jeremiah 17:9 universalizes the verdict: the heart is deceitful above all things and desperately wicked, or incurably sick. Paul gives a full indictment in Romans 3:9-18. Sin comes in degrees, and not everyone is a flagrant sinner; many try hard to do good as they understand it. Still, in God's eyes humans grow corrupt from a young age, and one sin is enough to incur the law's penalty of death. Honest people recognize that, like Israel, they carry a growing burden of sins through life.