Here is a post of mine which John Loftus at Debunking Christianity posted today. It was part of a larger discussion with David Marshal, a Christian author and blogger. See what you think. 
The post is here: 
http://debunkingchristianity.blogspot.co.uk/2012/04/explaining-faith-so-that-even-david.html 
And the larger discussion here:
http://debunkingchristianity.blogspot.co.uk/2012/04/less-evidence-you-havethe-more-faith.html#disqus_thread 

David

Part of the problem is that you are extracting these issues from their real world application and in a sense making them irrelevant. Let's apply the faith vs reason to real life instances:

 

1. Do you have faith that unicorns exist?

2. Do you have faith that heaven exists?

3. Do you have faith that gravity will cause this pen to drop?

4. Do you have faith that intercessory prayer works?

 

I presume the answer to the first question is no and second is yes. The third would also be yes. What is the difference between 1 and 2? As mentioned earlier, it is evidence. Now some of this may be personal experience, but it is still experienced by you, the sensory animal.

 

Let us look at 3. I have empirical and tested rational evidence that at every moment previously, then pen has fallen. using a method such as the scientific method I can establish that there is 'proof' that the pen will fall. It is not infallible (see the Problem of Induction) of course, but all it needs be is reliable.

 

Looking at point 4, we know that, from testing it scientifically (which is a reliable method for attaining knowledge), then intercessory prayer does not work. But if your answer to 4 was yes, then your faith is despite the evidence, which brings us back to our original issue with faith vs reason. There is no evidence, but presupposition in the truth value of the claim that prayer works.

 

For heaven, we know that the idea evolved such that it did not exist within the OT. The soul was an idea stolen from the Greeks of the Selucid Empire as they gave the Jews a hard time. This allowed them to understand how bad things could happen to good people. So, during the Maccabbean Revolt, Judaisim effectively 'invented' the soul and heaven. We have very good REASON to believe that heaven does not exist (including all the logical incoherenices with it - see my section on heaven in The Little Book of Unholy Questions and also in this video: http://www.youtube.com/watch?v=lrOwakB03QY). It is far simpler (Ockham's Razor) and logically and scientifically consistent to posit that heaven does not exist. Since you are the one declaring in the affirmative, then the burden of proof is on you.

 

Think of a justifiable belief as a closed jar. You can fill a justifiable belief up with two ingredients. Rational evidence (reason) and faith. Your belief in heaven is justified by yourself in this way: you have only assertion from a 2000 year old book. Period. It is not testable, no one has had experience of it and reported said experience. It is unfalsifiable. There is no other evidence at all, just conjecture and hope. Faith. So the jar is filled with a drop of evidence, and is then filled with faith. Your belief is justified by your faith.

 

Compare this with gravity. A belief in gravity is justified as follows: the evidence is multitudinous, empirical and all around us. It is testable, and most importantly, falsifiable, which is how science corrects itself. We can have a justifiable belief in gravity with a jar filled almost to the top with evidence. A small drop may be added for skeptical doubt (Problem of Induction).

 

The first belief is supported primarily by faith. The second primarily by rational evidence.

 

If you wanted to cross a road with your eyes closed, how would you justify the belief that you would get to the other side unhurt? Well, the road outside my house is a dual carriageway that has constant traffic. Using empirical and testable observations, I would have a belief in that I would get to the other side with my eyes closed unhurt defended by little evidence (I would also look at average speed, stopping distances etc). It would be a belief that could only be satisfied by faith.

 

If I had the same situation on a road with no traffic on in the country, I could have a justifiable belief defended with rational evidence that I would be unhurt. I would need little faith.

 

You, David, might say that in the first instance, God might save you. But even that has to be based on prior empirical experiences of God existing, of him stepping in on your behalf. Otherwise your faith would be entirely unwarranted (such as faith in Pegasus flying down and picking you up). Even that faith has a rational basis.

 

And that, ladies and gentlemen, is the difference, in a real life context, of the difference between faith and reason. Faith is the gap left in the justifiable belief jar which is left by evidence.

 

Of course, the simple way of looking at it is this: Ask yourself why you have faith in anything; faith in God.

 

I can guarantee, of course, that you would have a reason. It is not faith in a void. It is faith (albeit poorly) based on rational evidence.