Believing has both a head and a heart aspect, so while some non-Christians will need more help with one than the other, we can't ignore either one.
So what can we say when we are called upon to present the reasons why we believe?
First, I try to show that it takes faith to doubt Christianity, because any worldview (including secularism or skepticism) is based on assumptions. For example, the person who says, “I can only believe in something if it can be rationally or empirically proven” must realize that this itself is a statement of faith. This “verification principle” cannot actually be proven rationally or empirically, making it an assertion or a claim, not an argument. Furthermore, there are all sorts of things you can't prove rationally or empirically. You can't prove to me that you're not really a butterfly dreaming you're a person. (Haven't you seen The Matrix?) You can't prove most of the things you believe, so at least recognize that you have faith. I normally make this point by considering an objection to Christianity, to show that at the heart is some sort of faith assumption.
Let's take the example of suffering—-someone will say, “I can't believe in God, because how could a good God allow such suffering?” Put another way, they are saying, “I know for a fact that there can't be any good reason that a good God would allow this specific thing to happen.” Really? There could be all sorts of good reasons why God allowed something to happen that caused suffering, despite our inability to think of them. If you've got an infinite God big enough to be mad at for the suffering in the world, then you also have an infinite God big enough to have reasons for it that you can't think of.
Arguing with God
You have to show people that it takes faith to doubt Christianity. C. S. Lewis argued with God before his conversion that the universe seems so cruel and unjust. But then he asked himself, “But how had I got this idea of just and unjust? What was I comparing this universe with when I called it unjust? . . . Atheism turns out to be too simple” (Mere Christianity, Book 2, Part 1). In the natural world the strong eat the weak, and there's nothing wrong with violence. Where do you get the standard that says the human world shouldn't work that way, that says the natural world is wrong? You can only judge suffering as wrong if you're using a standard higher than this world, a supernatural standard. If there's no God, you have no reason to be upset at the suffering in this world. It takes faith to get mad at this world.
A gospel-shaped apologetic starts not with telling people what to believe, but by showing them their real problem. In this case we are showing secular people that they have less warrant for their faith assumptions than we do for ours. We need to show that it takes faith even to doubt.
British critic and former atheist A. N. Wilson wrote about losing his faith as a young man, influenced by British intellectual society, which assumed only stupid people actually believe in Christianity. “As a matter of fact however,” he argues, “it is materialist atheism that is not merely an arid creed but totally irrational. Materialist atheism says we are just a collection of chemicals, and it has no answer whatsoever to the question of how we should be capable of love, or heroism, or poetry if we are simply animated pieces of meat.”
A campus evangelist I once heard during the Vietnam protests pushed atheist students to recognize the clash between their moral relativism in regards to sex, and their moral absolutism with regards to international genocide. They had no answers. If there's no God, everything is permitted. Without God we're left with no basis for all that is most important to our lives: human dignity, compassion, justice. We have a problem.
Believing the Beauty of the Gospel
Which brings us to the final point, the solution to our problem. At some point you need to tell the Christian story in a way that addresses what people most want for their own lives, what they are trying to find outside of Christianity, and show how Christianity can give it to them. Alasdair MacIntyre said this about narratival apologetics: “That narrative prevails over its rivals which is able to include its rivals within it, not only to retell their stories as episodes within its story, but to tell the story of the telling of their stories as such episodes.” Read that sentence again.
There is a way of telling the gospel that makes people say, “I don't believe it's true, but I wish it were.” You have to get to the beauty of it, and then go back to the reasons for it. Only then will many believe, when you show that it takes more faith to doubt it than to believe it; when what you see out there in the world is better explained by the Christian account of things than the secular account of things; and when they experience a community in which they actually do see Christianity embodied, in healthy Christian lives and solid Christian community.
Editors' Note: This is a cross-post from Tim Keller's blog at Redeemer City to City.