@Aster, I can’t speak for anyone else in this thread but note that I won’t claim that it’s impossible that crop circles might be created by aliens. I also won’t claim that it’s impossible that a god or gods might exist; that’s why I call myself an agnostic. I’ll note that I don’t think it’s unlikely that aliens exist – quite the contrary, I’d think it was pretty strange if earthly life were a unique phenomenon. I just don’t think they’re probably messing around in our corn fields.
But I don’t consider it reasonable to heavily consider any possibility just because it’s not impossible. As @Qingu demonstrated, we can come up with any arbitrary claim (there are dragons living in the sun!) and it might be impossible, or very impractical, to assume a stance of uncertainty until proven one way or another. Using my dragons in the sun example, it would actually be impossible for me to prove to you that there aren’t dragons in the sun, because even if I sent a camera in there to look around and didn’t see any dragons, maybe the dragons are only visible on the gamma ray spectrum, or maybe they’re microscopic dragons. Is that really something I want to spend my resources investigating?
That’s why we have burden of proof. Many things are impossible to disprove, so instead, we try to prove that it is true, and if we are unable to find any evidence of such, we can draw our own conclusions. Maybe we just failed at finding the evidence, or maybe the evidence doesn’t exist because the claim really isn’t true.
One useful tool is Occam’s Razor, which says that when faced with possible explanations for an event, the explanation that requires us to make the fewest adjustments to our understanding of the universe is most likely true. So since our current understanding is that dragons don’t exist, it’s more likely that there aren’t dragons in the sun than that there are. And since crop circles can either be explained by aliens who, as far as we know right now haven’t been communicating with us at all, or man – which we do understand is entirely possible, since as you yourself say, men have admitted to making some crop circles – it’s more likely that the more “mundane” explanation is true.
I don’t see this worldview as dry or boring. Look at a DNA helix, or at Saturn through a telescope, and try to tell me again that reality as we know it, without any fantastic elaborations, is boring. I can’t possibly agree.