Does Christianity make a difference?

Edgar begins by outlining the main question that he is attempting to address: does the Christian faith actually make a difference? Does it bring about the kind of changes it claims to be able to make? He aims to counter the narrative often advanced by New Atheists like Richard Dawkins and Christopher Hitchens that Christianity (along with other religions) is poisonous and harmful. Edgar’s credibility in this task is increased by his frank admission of instances in which the church has failed. He is honest about these moments in Christian history, although he does frequently point out that the prevailing narrative (with regard to the medieval Crusades, for instance) unfairly portrays the actions of Christians. Edgar reminds the reader that evil will not be completely abolished until the final judgment. But his thesis is “that despite the numerous setbacks and weaknesses of the church, nevertheless we can point to substantial progress” (25).

Edgar’s first two chapters deal with the issue of making peace. The first chapter asks: why there is so much war in the Bible, if Christians are called to make peace? And how does Christianity respond to ongoing wars in the world today? Edgar answers by explaining that true peace sometimes requires a fight for justice, and he then makes a strong biblical case for just war. As a specific example, he admits that some Christians were complicit in the rise of Nazism, but that overall, a Christian understanding of just war and fighting to rescue the innocent motivated believers to work for the end of the Nazi regime.

The second chapter looks at the other side of the coin of making peace: how has Christianity brought about reconciliation between opposing parties? 

Chapters 3 and 4 deal with Christian contributions in the areas of social reform and healthcare. Edgar speaks at length of the contribution of William Wilberforce and other abolitionists motivated by their Christian faith to the ending of the slave trade in England and her colonies...In addition, he explains how modern medicine and many advancements in healthcare grew out of a Christian understanding of the curse of sin, as well as the biblical call to compassion for the suffering. 

Chapters 7 and 8 deal respectively with “Persistent Sins: Temperamental Inclination” and “Besetting Sins: Addiction.” In both, Edgar seeks to show that Christianity really works through its enabling of people to defeat anger, fear, lust for power, drug addiction, and pornography.

Chapter 9 concludes the book with a general discussion of human suffering and the gospel’s answer of hope in a dark world.

http://www.booksataglance.com/book-reviews/christianity-really-work-william-edgar/

I'd like to take a stab at this question myself:

1. Many atheists do think Christianity makes a difference. That's why they're implacable adversaries of Christianity. They think it makes a difference for the worse. 

2. As long as they're atheists, we won't be able to convince them that Christianity is generally a force for good. That's because Christians and atheists often disagree on what is good. They think biblical ethics is sexist, racist, sadistic, homophobic, transphobic, xenophobic, misogynistic, violent, and generally intolerant. The two camps are becoming increasingly polarized. Atheism has no positive identity. Atheism is reactionary. Western atheism is defined by opposition to Christianity.

3. One difficulty is the definition of Christianity, for Christianity isn't monolithic. To the contrary, the Christian faith is notorious for its many factions. To some degree, I think traditional European anticlericalism was justified by the venality of the Catholic church. It would, however, be illogical to blame Protestants for Catholic misconduct. You can't reasonably blame Protestants for the Inquisition or pederasty among the Catholic clergy. Protestants have their own problems, but you can't reasonably blame Presbyterians for Luther's anti-semitism, or Anabaptists for Confederate Presbyterians. 

4. In what respect does Christianity claim to be able to change people, and change society? Christianity can't be expected to directly influence non-Christians. In the nature of the case, it primarily changes Christians from what they'd otherwise be. It's no failure of Christianity that non-Christians don't think and behave like Christians. Naturally it doesn't work for people who disagree with it. Who lack faith. 

5. If a society becomes predominantly Christian, that has a leavening influence. Insofar as policymakers are Christian, law, public policy, and public institutions have a trickle down effect. Where it's been tried and applied, Christianity has made the world a much better place. And even where there are notable failures, the non-Christian alternative will be rotten in a different way. 

6. According to Scripture, Christians remain sinners. There's no guarantee that a Christian will be able to overcome an addiction in this life. While Christianity can and does produce many dramatic examples of personal and social transformation, total transformation lies in the world to come. That's the hope that keeps us going.