At one time, it would have cost you a pretty penny to finish off your Piper book collection.

A few fanatics would pony up what it took to obtain a Cambridge-University hardback or Baker softcover of John Piper's out-of-print dissertation Love Your Enemies. But most of us saner types, even if we claimed to have "read everything by Piper," never had access to the monograph he wrote in Germany in his mid-twenties.

But Crossway has stepped in to fill the gap. The just-released 2012 republication of Piper's dissertation retains the original text — "we have let it stand as it was for historical purposes," says Piper — and adds a new preface in which Piper reflects on the book, and his three years in Germany, now four decades later.

You might ask, Is there anything you'd change forty years later? Piper anticipates this question. He says he would not approach the topic in the same way.

If you want to see how I would write a book today on Jesus’s command to love our enemies, read What Jesus Demands from the World (Crossway, 2006, especially chapters 28–31). That book reflects my seasoned judgment about how to do Gospel studies for the greatest payoff.

Piper also adds this:

One of the most important changes I would make in my doctoral dissertation, if I wrote it today, would be to make the cross of Christ far more prominent. It is there. And it is crucial. But it is not prominent. And that is not as it should be. I hope that what I have said and written since then has set the record straight.

Our only hope for loving our enemy is to be a new creation in Christ. And our only hope for being a new creation in Christ is to be reconciled to God through the death of his Son. "If anyone is in Christ, he is a new creation. The old has passed away; behold, the new has come. All this is from God, who through Christ reconciled us to himself" (2 Corinthians 5:17–18).

The only hope that we might love our enemy is that God loved us when we were his enemy. "If while we were enemies we were reconciled to God by the death of his Son, much more, now that we are reconciled, shall we be saved by his life" (Romans 5:10). This is the great root of the good tree we are becoming: "Forgive one another, as God in Christ forgave you" (Ephesians 4:32). Turn the other cheek — seventy times seven (Matthew 18:22). Love does not keep an account of wrongs (1 Corinthians 13:6). "Bless those who persecute you; bless and do not curse them" (Romans 12:14).

Jesus is the great example here, and the inimitable substitute: "When he was reviled, he did not revile in return; when he suffered, he did not threaten, but continued entrusting himself to him who judges justly" — that’s the example (1 Peter 2:23). And "he himself bore our sins in his body on the tree, that we might die to sin and live to righteousness" — that’s the substitution (1 Peter 2:24). What he has done for us is the ground for what he does in us. We can become a good tree only because he was cursed for us on a horrible tree (Galatians 3:13).