How can evil have a good purpose?
Evil can ultimately have a good purpose because of the sovereignty of God.
What I mean by the sovereignty of God is his absolute right, power and de facto intention to govern all things according to the counsel of his will, without any decisive influence from outside his will. And the word "decisive" is very important, because clearly our prayers are heard by God, and he does things he would not have done had we not prayed. That fits in my understanding of sovereignty, because he ordains the prayers, and therefore God ordains that he be influenced by events in the world. But having foreseen them and ordained them, it is not from outside of him ultimately or decisively that he is acting.
And so sovereignty is God's decisive self-reliance, self-determination. And there is no such thing as ultimate human self-determination. Humans have measures of self-determination, but they are not ultimate, because God ultimately governs and guides all of human willing and all of natural events. That's what I mean by the sovereignty of God.
That includes his sovereignty over evil. That's what the book Spectacular Sins is about: spectacular sins that God governs, that God ordains that they come to pass. The Lamb was slain from before the foundation of the world in the mind of God (Revelation 13:8), which means that before there was creation and before there was the Fall and before there was Satan, there was Christ contemplated as slain. Which means God was contemplating the sin for which he was slain. Which means that sin was in the plan, from before there was any so-called freewill Fall.
So that's what the book is about, and that's why sovereignty relates to sin so crucially. And the reason it is so crucial is that it helps us address the next question: "How could you get any comfort by a God who is out of control?"
After the planes flew into the Twin Towers in New York, I was interviewed and people would ask me, "Where was God in this?" I said, "Well, God could have very easily blown those planes off course by a little puff of wind, and he didn't do it. Therefore God was right there ordaining that this happen, because he could have stopped it just like that." Everybody who believes in God should say that, because that is how powerful he is, as it was said of Jesus, "The winds obey him" (Matthew 8:27). And so just a simple wind by the command of Jesus would have blown those planes away and they would have crashed and 60 people would have died instead of thousands of people. But he didn't do that. Why is it comforting to believe that?
The answer is because there are 10,000 orphans who wonder if they have a future. Will they have a future if God isn't powerful for them? I'm coming to those families and I'm saying when they ask me, "Do you think God ordained the death of my daddy?" I say, "Yes. The Lord gives and the Lord takes away. Blessed be the name of the Lord. But the very power by which God governs all evils enables him to govern your life. And he has total authority to turn this and every other evil in your life for your everlasting good. And that's your only hope in this world and in the next. And therefore, if you sacrifice the sovereignty of God in order to get him off the hook in the death of your daddy, you sacrifice everything. You don't want to go there."
The sovereignty of God, while creating problems for his involvement in sin and evil, is the very rock-solid foundation that enables us to carry on in life. Where would we turn if we didn't have a God to help us deal with the very evils that he has ordained come into our lives? So yes, absolutely, I believe in the sovereignty of God and I believe in its comforting effects.