Have you ever marveled at how many things you believe without evidence? It turns out to be most things. I rarely have time to consult the peer reviewed scientific literature before doing something such as, for example, shaving and whistling at the same time. I’ve never seen any evidence that doing those two things simultaneously is dangerous, but I can’t rule it out. So I believe, without conclusive evidence, that it’s safe.
When you don’t have conclusive evidence, you have to rely on common sense. That’s the same method employed by the first guy who died from eating a poison mushroom. I believe his last words were something along the lines of “All the OTHER mushrooms were fine! Gaaaaaak!”
Mostly I believe whatever people tell me, as long as it sounds somewhat reasonable, and until someone else tells me it’s wrong. For example, I believe that the theory of evolution is useful for geologists searching for oil. Many people have told me so, and I’ve heard no argument to the contrary. It certainly sounds like one of those things that could be true. But it makes me wonder if creationist geologists are worse at finding oil than atheists. Somewhere in Calgary I imagine a conversation between a creationist geologist and his boss:
Boss: “Matthew, why haven’t you found any oil? All the other guys have.”
Matthew: “Well, I’ve been drilling everywhere looking for carved stone tablets from God but all I find are these stupid fossils.”
I’m told that evolution is useful for a whole range of scientific things that I don’t know about or don’t understand. For example, I’m told that if you don’t believe that mammals evolved from lower life forms you’d be a crappy microbiologists. Every time you observed some viruses acquiring immunity you would stop working on a vaccine and sacrifice your first born son.
So I believe that the theory of evolution is useful because no one has told me otherwise and I don’t have the time to check into it. But just to be safe, I don’t believe it when I’m shaving.