In the first chapter of his excellent, college-level presentation of the serious reasons for believing the Christian faith, William Lane Craig addresses some of the issues raised when we try to show people Christianity is true. He writes:

…in answering the question “How do I know Christianity is true?” we must make a distinction between knowing that it is true and showing that it is true. We know Christianity is true primarily by the self-authenticating witness of God’s Spirit. We show Christianity is true by presenting good arguments for its central tenets.

What, then, should be our approach in using apologetics with an unbeliever? It should be something like this:

My friend, I know Christianity is true because God’s Spirit lives in me and assures me that it is true. And you can know it is true, too, because God is knocking at the door of your heart, telling you the same thing. If you’re sincerely seeking God, then God will give you assurance that the gospel is true. Now to try to show you it’s true, I’ll share with you some arguments and evidence that I really find convincing. But should my arguments seem weak and unconvincing to you, that’s my fault, not God’s. It only shows that I’m a poor apologist, not that the gospel is untrue. Whatever you think of my arguments, God still loves you and holds you accountable. I’ll do my best to present good arguments to you. But ultimately you have to deal, not with arguments, but with God himself.

There are, of course, other important ways Christians show that the message of Jesus is true. There is the testimony of godly lives which are lived out consistently, even in tempting or trying times. Sometimes there is the miraculous power which God can work through believers (at His discretion). There is the faithful proclamation of the word of God itself (which God often applies directly to people’s hearts with His own power). I am sure Dr. Craig would agree with all of this. What he’s doing here is making a helpful distinction for Christians to remember when we begin to get excited about all the different kinds of compelling evidences which show how reasonable it is to believe that Jesus is Lord.

His main point is just to remember that, no matter how good we get at handling these different lines of evidence, they alone do not constitute the foundation of our knowing–for that we rest on the One who’s in us, interacting with our hearts and minds and granting us assurance when we struggle.

I would add, though, that the Spirit does not work apart from all the evidences God has given, but along with those evidences. Everyone should believe that Jesus rose from the dead, and therefore is the Lord, and then, when you study his life and teachings… that all of the scripture written before him is true, since he testified to its truth. And everyone should believe these things because of the evidence of the universe itself, the nature of humanity as we find it, and the historical weight of the evidences for the resurrection of Jesus Christ.  These lines of evidence can be, as Dr. Craig points out, the kinds of evidences we present when people ask us why we believe.

And yet, we all know that there are times when our personal hold on this kind of evidence might not be as firm as we’d like. Sometimes we don’t have access to all these lines of evidence. Or sometimes we hear them challenged, and we don’t immediately know how to answer the challenges. Or sometimes painful things happen to us, and evidence of this kind feels far away and unhelpful. What then?

And this is, I think, the most helpful part of Dr. Craig’s observation here. Though these historical, observable evidences are actually enough to make us liable to believe in Jesus Christ, God, in his mercy and generosity of spirit, has not left us only external evidence. He also comes to us, personally, by His Spirit, and lives in us, and testifies to the truth of everything the Bible says. If we’ll listen to him, and yield to him, He’ll work the kind of assurance in us that we need to walk through a disheartening, confusing, and often painful world.