Many people, especially religious pundits who want to knock "cold, logical science" down a few notches, claim that science is as faith-based as religion. I would tend to agree. Those who disagree argue that science relies on painstaking experimental method and proof to back up its theories--which is true, but only to a certain extent. When it comes to the things that science just can't determine (or at least hasn't determined yet), we depend utterly on faith.
A specific example of why scientists are illogical, however, is evident: the afterlife (or lack thereof). When you die, if any of the major religions are correct, you proceed to some sort of afterlife. If you're an atheist, you believe (mmm, sounds faith-based) that there is no afterlife. Or at least, there's no afterlife with God in it.
But here's the clincher: if a "God" does exist, then you are screwed--at least according to those religions again, since the non-believer infidels usually enjoy a fate such as being "consigned to suffer the flames of Hell for all eternity". :fear: Nicer religions stick them in limbo or some such dimension like that. What it comes down to is: believers prosper, non-believers don't.