When a Christian comes up against difficult intellectual arguments against Christianity, there are two paths that can be taken (and indeed, I'm seeing this split occur in the Evangelical community). First, one can take refuge in the perspective so dominant in our culture that religious values and spiritual questions are "above the line" of rationality (as Francis Schaeffer put it)--beyond the reach of intellectual investigation, attacks, or proofs. Spiritual "truths" are not in the same category as material truths, so challenges are irrelevant.
On the second path, one sees all of true reality as a single whole--spiritual and material--existing as it is, never as its opposite, and capable of being known (never exhaustively, yet truly) through observations, rational thought, and revelation. But since all of reality is the same kind of reality, this means there is only one truth about what exists as the spiritual aspect of that reality. If the Christian who believes this about reality cares about truth (i.e., what actually exists), he must face the difficult questions and struggle through them, working to find the answers, for he's not willing to place his trust in something that is not there. If Christianity is true, it will hold up to scrutiny; if it is not true, this Christian doesn't want to believe it.
Can a Christian persevere through mockery, persecution, or a time of dry emotions and few experiences without the confidence that he is held up by a solid, true reality? Can he act consistently and deeply on a faith he doesn't believe represents what actually exists? I don't see how the first path can sustain the confidence needed for sincere, enduring love, service, and sacrifice. On the other hand, I think the second path leads to a spiritually deep, authentic, persevering church.
For this very reason, Schaeffer encourages believers to grasp the reality of Christianity in his book, He is There and He is Not Silent:
The truth of Christianity is that it is true to what is there. You can go to the end of the world and you never need be afraid, like the ancients, that you will fall off the end and the dragons will eat you up. You can carry out your intellectual discussion to the end of the discussion because Christianity is not only true to the dogmas, it is not only true to what God has said in the Bible, but it is also true to what is there, and you will never fall off the end of the world! It is not just an approximate model; it is true to what is there. When the evangelical catches that--when evangelicalism catches that--we may have our revolution. We will begin to have something beautiful and alive, something which will have force in our poor, lost world (p. 289).