"Even things that are true can be proved." -Oscar Wilde
There is a tendency among modern Christians to think of the Faith as something that can and should be proved and to undertake projects to do so. We use words like "evidence" and "verdict" and "incontrovertible" in an attempt to create some kind of coercive logical sequence to compel people to believe.
It is thought that once you understand the facts well enough, you will become a Christian.
I submit that this is not in fact the true case, and when it is represented as the true case, the effects are disastrous.
God always leaves a gap in the evidence - a place for faith to fill. Faith is defined in scripture as "the evidence of things not seen," i.e., the piece that makes up the gap. Without this gap there is no volition, no decision, and no personal responsibility. If the evidence is simply overwhelming, there is no need for faith.
The problem is that we have accepted the argument on the world's terms. And so we seek to justify faith at the bar of rationality. This is futile, for faith by it's very nature is designed to transcend rationality and access the ultimate. If rationality is granted to be the ultimate, the fight has already been lost.
It is vital that we are not embarrassed by this. Modern thinking only allows three categories of rationality: rational, irrational, and nonrational. Faith is superrational. Enlightenment thinking may have done more damage to the Church than Postmodernism will ever do.
Hopefully this realization will begin to inform our witness to those outside. Our witness is just that: witness. Demonstration. Incarnation. Persuasion. Faith is faith. Don't try to make it something less.
There is much the Church can do to make it possible to believe. It is when the Church attempts to make it impossible to disbelieve that she oversteps the wisdom of God and her offering becomes a strange fire. In an effort to make faith plausible, we may in the end make faith unnecessary.