If God is in control of everything, can Christians sit back and not bother to evangelize? Or does active evangelism imply that God is not really sovereign at all? J.I. Packer shows in this classic study how both of these attitudes are false. In a careful review of the biblical evidence, he shows how a right understanding of God's sovereignty is not so much a barrier to evangelism as an incentive and powerful support for it.
The relationship between God's sovereignty and man's responsibility is a very confusing one. On the one hand, we see in the Bible that God is sovereign over even the actions of man, since God has "mercy on whom He will have mercy, and whom He will He hardeneth" (Rom. 9:18). Even Christ's death on the cross was not done outside God's control, but He was "delivered by the determinate counsel and foreknowledge of God" (Acts 3:23). This is all good and glorious as we can rest assured in God's providence and care for us, knowing that nothing will separate us from the love of Christ, not even our own sins.
But some people lean too far toward God's sovereignty and forget all the places in Scripture that refer to commands to *do* something. "Work out your salvation with fear and trembling" (Philippians 2:12). "Give diligence to make your calling and election sure" (2 Peter 1:10). Though we know that Christ is sovereign over our works, we also know that we are entirely responsible for our works, and we mustn't forget either principle.
Having said all this, I really enjoyed this book because J.I. Packer helped me understand all this. He showed that divine sovereignty and human responsibility are really not at odds with each other, but both promote sanctification in God's people. He showed that there is an antinomy between the two (which has been mentioned in another comment) and even though we don't entirely understand this paradox, we must accept it as God's Word shows it to be true.
Having dealt with this issue, Packer then applies it to evangelism. He shows that only assurance of the sovereignty of God can give us true success in evangelism, because then we will not have to come up with clever methods to get people into church, or to entice them into the faith. When you are assured that God is the one that brings people to faith, you can simply proclaim God's gospel with love, and God will bring converts.
Packer also shows that a proper understanding of human responsibility helps in evangelism as well. The burden of evangelism is still pressed upon you, and you don't sit back as the hyper-calvinists do. In addition, you can be confident in your calls for repentance and for your audience to be baptized and enter God's Church.
Only when you hold to both sides of this paradox can you understand evangelism properly. Packer gets the paradox, and he explains and defends it *very* well.