I will contribute with my own witness about it. My conversion was firstly intellectual and only then it was related to faith. I will not bother people with the story itself, but I'll go straight to the thinking behind it.
Some background is necessary though. I was never an atheist. At some points I was agnostic, in adolescence I got involved with spiritism and later with compared religion with that blasé pseudo-intellectual self-satisfied vanity of being able to understand all religions deeper than their own believers, see the truth past their superstitions and have an independent, free-thinking personal relation with Divinity, whatever it could be in itself. I thought it was self-sentient, intelligent, free-willed, but nothing more than that.
When I decided to seriously study Christianity, I had already read many books about Christianity. But that is different from a serious study. I was, even in my best moments, contaminated by the many cultural prejudices against Christianity and the Church our era has. Any conspirationist theory about the resurrection was better and more probable than a dead person actually rising from the dead. In mere speculative terms, it was easier to believe that some sort of big lie was plotted, even if with good intentions, than that a man resurrected. Rationally, it makes sense. The story could have been inveted based on previous mythologies. It was sufficiently similar to then to justify that. Something historical might have happened, but overlayed by myth and superstition. Anything. But not the resurrection.
I then read C.S. Lewis. It was a shock. Not much because of the arguments in themselves, but because I was looking at what was, until then, a mythological inexistant creature to me: an intelligent educated Christian. Then came Thomas of Aquinas, Chesterton and others. But it was Lee Strobel and his "The Case for Christ" who showed me the right angle to look at this issue.
Skeptics usually ask for proofs or at least, outstanding evidence since it is an outstanding claim. Some atheists do convert, so it shows that there are enough good evidence around for the subject, but, of course, there are those who remain unconvinced. It may be the case that they are perversely obsessed with their little confortable world as some claim, but I suppose these are a minority. Some are probably like I was, they have not yet grasped what *kind* of *fact* is under scrutiny in this discussion: it is a historical fact.
When I say it is a historical fact, I am not stating the conclusion before the analysis. What I am saying is that we are discussing if this a historical fact or not, that is, *if* it is a fact that happened some two thousand years ago, it has to be evaluated in the same way any historical fact is. So, this limits what kind of extraordinary evidence has to be provided. Whatever it is, it will share the nature of *any* historical fact that happened in that same period (it is not scientific to expect the same kind of evidence from a fact in the last century and a fact 10 thousand years ago).
I will not summarize the book, since some few lines would just do it a disservice. I recommend it for everybody who needs or wants an intellectual rational approach to the issue: http://www.leestrobel.com/store.php
But, moving on, once I started analysing the resurrection, and its competing theories, as history, and not artificially demanding more evidence than something that would have happened 2 thousand years ago could give, and with further help from the book "Hidden Gospels: How the Search for Jesus Lost Its Way"http://www.amazon.com/Hidden-Gospels-Search-Jesus-Lost/dp/0195156315/ref=sr_1_2?s=books&ie=UTF8&qid=1284671194&sr=1-2
by Philip Jenkins it became clear to me that it was a reasonable and even probable explanation for all the facts surrounding it.
You see, to me, the main evidence for the truth of Christianity, when you are searching from the outside, is in *history*. Not on philosophy, or logic, or common sense. There is no set of logical sylogisms that can proove that on May 3rd, 1981 I had eggs for lunch. There might be only the kind of "proof" archeology or history provides. Some centuries from now, even my own existence will be doubtful if even remembered by someone. Nobody will be able to give ultimate proof that I existed. Historically, one could make a "strong case" and that is as far as one can go. Now, of course, there are degrees of certainty in this. One can reasonably be more sure that Julius Ceasar existed than that any of his generals and for various reasons: there are more documents about him, more references, etc, etc. The whole set of evidences that are used by historical science. One of the things "The Case for Christ" does is to show convincingly that the number and quality of references about Christ are larger and better than, for example, Alexander, the Great.
When you come to this point, then, and only then, you deal with the issue of faith, that is, of trust. If I can have more or less the same intellectual degree of certainty for the resurrection that I can have for other known historical facts, will I trust this and treat it as if it is true or not? *This* is the step of faith, after the "preparation" of intellectual effort. There is an advantage about this possibly historical fact that no other has: *if* it is true, and *if* I trust it, according to the theory, my life will change in the very present I live. It may be a radical change as a miraculous healing or more subtle like a change of direction in the meaning of my life. Plus, this change will not come about randomly, but it is supposed to happen in a way that will show that there is a *person* guiding events toward a certain direction. There will be a "plot" so to say, and this "plot" will converge with the intentions, wishes and character of that Jesus. But if it is true the change will happen, and this a test that can be done.
I did the test, and many others have. In fact, all those who did it, consistently verified that the changes have happened. Now, it is not the same kind of knowledge we have that 1 + 1 =2. It is the same knowledge that a person exists. It relies on a series of subjective perceptions some of which you'll be the only one to know. It is a knowledge that is not easily socialized. Scientific knowledge is easily socialized. You can say it almost imposes iself. The airplane will fly whether you believe in aerodynamics or not. But, like any human relationship, you just enjoy the friendship of a person, if you feel and act like a friend towards this person. A friendship is no less true than a mathematical equation. But it is not an impositive truth.
Our relationship with God is more like a friendship than like a mathematical truth. It is love between two people. And here resides its excellency and its difficulty.