re: Science and atheism
As a friend of mine recently put it, "faith is the critical leap from ignorance to willful ignorance."
As an atheist, I do not have "faith" there is no God. Faith is the quality that would require me to continue denying the existence of God even in the face of unequivocal evidence that He does.
I have no reason to believe in God in the same way that I have no reason to believe in mermaids. If you really nailed me down in a strict logical sense I'd have to admit that I don't know whether mermaids exist -- I only know that I have never seen any evidence of them. However, if I were to lead in to a conversation about mermaids by saying that, most people would assume I was a cagey believer, so I say something that's going to more accurately convey my position: "there's no such thing as a mermaid."
Here's the trick: whether I'm talking about mermaids or God, I'm willing to be wrong. I don't feel any need to hedge my statements about the existence of these things, but if you show me a mermaid, I'll shrug my shoulders and say, "Hunh. My bad." That's what separates me from a religious person. Religious people attach moral consequences to adherence to their specific religion. Atheists (at least, atheists like myself) are not attached to atheism in itself, but instead to the idea of knowing reality as accurately as is within their power based on the evidence at their disposal. If the evidence indicates something other than atheism is warranted, then so-long atheism.
It is true that "absence of evidence is not evidence of absence," but absence of evidence is the best we're ever going to get. There are a whole lot of things that don't exist -- flying purple alligators, say -- and not one of them leaves a single trace of evidence that it does not exist (nonexistent things are funny that way). We don't hold every potentially existent thing to exist until proven not to; that would just be silly. Quite the contrary, since only existent things are even theoretically capable of leaving evidence of their metaphysical status, the only sensible criterion we can establish is to hold things to be nonexistent until we see some of the evidence that, if they exist, they might leave behind.
This leaves a whole theoretical class of objects that both exist and fail to leave observed evidence of their existence. It is at this point that pragmatism comes into play, because anything that leaves no trace of its existence may be safely treated as if it does not exist. If a previously unobserved item is to become in any way relevant, it'll have to do something observable, and then we can prove it exists.
No one recognizes lack of belief in mermaids, ghosts or flying purple alligators to represent a positive philosophical claim. Only the social pressure associated with religion leads anyone to make such a claim with regard to disbelief in God.
and I must say that summarizes exactly something I've been trying to say for years.