Science is built on faith. I mean that in both the good sense and the bad sense.
For me, "faith" in the good sense means scientists believe in their results and those who choose to believe in science trust that people smarter than us are doing their best to come up with objectively verifiable data. The best scientists realise that there is unlikely to ever be a universal "truth" but through diligent work they add a few more pieces to the puzzle.
While I think it's insane for a scientist not to have faith in their work and believe in their results, history shows us that many of the most dearly held scientific "truths" will end up being modified or completely invalidated by subsequent discoveries.
From a Joe Public point of view, it simply isn't possible to have a deep understanding of how scientists come to their conclusions. These people spend years (usually their whole lives) specialising in their fields. Reading a 1,000 page book might give good insights into the science behind the latest theories and/or discoveries but you won't understand it in the same way as the scientists doing the work. Anyone who says they do really understand it is either in 0.0001% of the population or they're a wanker. Do the math and you'll see what I think of people like this.
So basically by definition, if we say we believe in scientific principles we believe that based on faith. This isn't intrinsically a bad thing, like most faith it depends how you apply that faith that counts. Personally, I apply it along the lines of "I believe the majority of scientists are acting in good faith; I believe their greater goal is to expand knowledge, not prove they're better than everyone else; I believe the experiments conducted to verify important theories were rigorous, repeatable and peer-reviewed; I believe the best scientists are always asking questions because the currently believed answers might be wrong."
So that's my version of science=faith in a good way. Then there are, of course, those who express their faith in science in what I see as a bad way. I find it mildly amusing when people who claim to be pro-science and anti-religion aggressively attack religion in the name of defending science. Now, I understand the value of an angry outburst but when supporters of science want to argue that following a religion makes you stupid by definition then they're falling into the same trap of zealotry.
I am all for aggressively fighting for the separation of science and religion. The idea that creationism should be taught alongside evolution to "teach the controversy" is utter bullshit. That goes double for creationism's lying scumbag cousin "intelligent design" - I mean, fuck me, just admit you're creationists. It all boils down to "magic man in the sky done it" which, frankly, doesn't cut it as a scientific theory.
You shouldn't "teach the controversy" in science classes because there is NO scientific controversy regarding evolution versus creationism. There is plenty of controversy within the details of evolution but that isn't the same thing. If evidence ever comes to light that displays fatal flaws in evolutionary theory I'm quite confident that the unmitigated bullshit that is creationism isn't going to magically become any less of a fairy story.
I actually understand the impulse to scientific zealotry. If you dedicate your life to learning about the natural world in what you see as an objective way and find yourself having to defend your views against people coming from a completely illogical position, well... Why not simply call them fuckwits and be done with it?
My personal belief is that fundamentalists of any religious stripe tend to be utter morons. Maybe they're not morons in the literal sense of being unintelligent (although a hell of a lot of them most definitely are) but they sure seem keen on crushing knowledge that challenges their "magic man in the sky done it" view of the cosmos. But there is not a straight line of logic between "fundamentalists who try to undermine science are fuckwits" and "anyone who believe in god is an idiot." It can be comforting to think so but it simply isn't true.
Likewise, many supporters of science over religion are loud mouthed idiots who should sit the fuck down and shut the fuck up. I've had the amusing experience (more than once) of having supporters of science saying that it isn't possible to be stupid and support science over religion because you need to be intelligent to have a skeptical mind. This is a seductive line of reasoning but I think it has two major flaws.
First, as soon as someone tries to support a position with circular logic (it is what it is because it is what it is) I get suspicious. Second, it presupposes that the people who believe in science actually understand what it is they are supporting. It isn't possible to understand current scientific thinking on evolution (for example) in any meaningful way without years of study. So the scientists dumb it down for us poor schmucks so we have an inkling of what they're going on about.
It all comes back to belief in science being a leap of faith. I happen to believe it's an intelligent leap of faith that respects the logical and rigorous application of scientific inquiry. I also believe that far too much religious teaching discourages and even punishes critical thought. But a lot of demonstrably stupid people champion science over religion. To pretend otherwise is to ignore a huge body of evidence.
My personal favourite is when you refer to scientific zealots and you get someone jumping all over you ranting about how there is no such thing as a scientific zealot. Show me a scientific zealot, they demand! Uh, you got a mirror handy there, champ? Actually, the level of narcissism on display with people who feel compelled to trumpet their intellectual superiority leads me to suspect they have many, many mirrors on hand. But actual self-reflection and introspection aren't their strong points.
Interestingly, I've found you get the same response if you pick on zealous supporters of Israel, Apple and/or Agile software development methodology.
So the fact that I think science (as opposed to religion) is the way to discover the truth doesn't change the fact that I've made that decision based on faith. I also believe science thrives on the questioning of it's conclusions - an area where religious beliefs (or at least religious institutions) tend to not hold up so well. But I also think scientific zealots can be more deluded than religious zealots. At least religious zealots tend to admit what they are.