In an encounter in Acts, the Apostle Paul is accused of being out of his mind. Paul replies, "I am not insane ... What I am saying is true and reasonable" (Acts 26:25, NIV).
As a former atheist, I had to come to terms with a lot of issues before accepting Christ and realizing that Christianity makes a lot of sense. I recently completed a unique apologetics book that will address the case for and against Christianity via a series of diagrams and accompanying commentary. (Christian apologetics, by the way, is the rational defense of the faith.)
One chapter makes the claim that Christianity is the best explanation of reality and offers six key lines of evidence in its support. First, truth is objective and we can know reality. Second, God exists and has revealed himself. Third, the Bible is reliable. Fourth, Christ rose from the dead. Fifth, Christianity best explains reality. Sixth, religious experience supports Christianity.
These aren't the only reasons Christianity is "true and reasonable." Also, keep in mind that these evidences can work together to make an overall case for Christianity. In other words, each point need not be in isolation from other lines of evidence.
In the chapter, after making a case for each point, I go on to offer several objections to those six premises. This helps see arguments from different perspectives, which can help strengthen our own position as we think through criticisms of ideas we believe are true. I then offer rebuttals to the objections.
I also present diagrams and arguments from opposing viewpoints, which puts me in the position of having to defend the claims of atheists or pantheists, for instance. Some of those topics include the claims that since evil exists, God does not exist, or the arguument that belief in God is delusional.
The idea is to help us think critically about ideas and see that there are many different viewpoints to consider and evaluate. There's a great and relevant quote in the C.S. Lewis novel That Hideous Strength. One character remarks, "I suppose there are two views about everything." Another replies, "Eh? Two views? There are a dozen views about everything until you know the answer. Then there's never more than one."
One of my tasks as a curriculum writer at Sonlight is to help children think through all kinds of ideas, even if those ideas may clash with existing viewpoints. This is especially crucial as children get older, but it's a good idea to start early. Our goal at Sonlight is to educate, not indoctrinate. This means giving children the information they need to grow in their faith and equipping them to wrestle intelligently with ideas.
Why believe Christianity? It's "true and reasonable." We have good evidence in support of its claims. But this doesn't mean we can just ignore the objections. Fortunately, we have good answers!