Question: If Satan is the cause of evil, why did God drown all human being during the time of Noah, but left Satan?
The question assumes that Satan is the ultimate cause of evil, but that premise can be rejected as false because the Bible does not make that claim. Scripture consistently teaches that evil originates in the will of moral creatures—angels and humans—who freely chose to rebel against God. As James 1:13–14 (ESV) says, “Let no one say when he is tempted, ‘I am being tempted by God,’ for God cannot be tempted with evil, and he himself tempts no one. But each person is tempted when he is lured and enticed by his own desire.” Satan is a tempter, but not the creator of sin. He does not cause or force persons to sin. Evil arises when God’s creatures, endowed with freedom, turn away from His holiness toward something that appears more gratifying. Humans do not need Satan as a catalyst for sin or evil; they have that capacity within themselves. Dr. R.C. Sproul often emphasized, sin is not a “thing” created but a privation—a corruption of good, rooted in the creature’s willful disobedience.
So why did God judge humanity in Noah’s day while allowing Satan to remain? The flood account in Genesis 6–9 shows that “every intention of the thoughts of [man’s] heart was only evil continually” (Gen. 6:5). Humanity had so corrupted itself that God’s just response was global judgment, sparing only Noah and his family by grace. Satan was not the one filling the earth with violence—human beings were. Philosopher and Christian apologist William Lane Craig argues that moral responsibility lies with the agents themselves; temptation does not excuse sin. The flood was thus a picture of God’s holiness and justice in action against a specific generation’s wickedness, not a judgment on Satan’s rebellion.
Furthermore, God’s providential plan required that Satan be allowed to remain until the appointed time of final judgment. Sproul noted that God permits Satan’s activity within divine sovereignty to magnify His own glory in redemption. Josh McDowell reminds us that apologetics begins with the cross: Christ’s victory required that evil be displayed in its fullness so that God’s grace and justice might be perfectly revealed. Revelation 20 assures us that Satan’s doom is certain—he will not escape judgment. In the meantime, as Geisler wrote, “The existence of Satan provides the context for the triumph of Christ’s kingdom, where grace abounds over sin and light shines in the darkness.”
In short, God drowned humanity in Noah’s day because human beings were guilty of wickedness. Satan may tempt, but he is not the ultimate cause of evil—our own sinful desires are. God spared Satan temporarily to accomplish His greater redemptive purposes through history. The flood, the cross, and the final judgment each show that God is sovereign, just, and merciful, and that evil will not prevail.