"Imagine a puddle waking up one morning and thinking, 'This is an interesting world I find myself in, an interesting hole I find myself in, fits me rather neatly, doesn't it? In fact it fits me staggeringly well, must have been made to have me in it!' This is such a powerful idea that as the sun rises in the sky and the air heats up and as, gradually, the puddle gets smaller and smaller, it's still frantically hanging on to the notion that everything's going to be alright, because this world was meant to have him in it, was built to have him in it; so the moment he disappears catches him rather by surprise. I think this may be something we need to be on the watch out for."—Douglas Adams, Is there an Artificial God?
Arguments for the existence of God based on observation of nature hinge on the idea that the universe is so complex that it would have taken a powerful intelligence to make it. Suppose that were true: the most that that argument could ever possibly conclude is that something very complex and big exists. I call that complex big thing the universe.
To set up any sort of proof for the existence of God, you have to answer the question, "Which God?"
When I say God, I mean someone powerful, personal, and good, someone who evokes worship from me. Isn't this why anyone would be concerned with the idea of God? If we're just talking about some ambiguous big thing, who cares what we call it or how we deal with it? The questions about God are all questions about meaning.
And, by powerful, I mean powerful enough to make the big bang happen. I don't want to worship Barack Obama by mistake.
That God would be personal is important, too; I think the cosmos is beautiful, but I don't worship it. What do you give a cosmos that has everything?
Well, not all arguments for the existence of God from study of nature try to advance the idea that God must be more complex than the universe. Some try to argue that God must exist because the universe is good. The universe would have had to have been made by something big, complex, and good. I think that this is what deists believe, at least, this is what my rabbit tells me she believes, and she's a deist.
Even if there is this complex, big, good thing, I can't tell if it has beaten or wooed me into good behavior, and I don't know why either of us should be concerned at all with the other.
All of these arguments from nature depend on some sort of embiggening assumption, that if the universe has some property, it must have been made by something that displays that property even more so. It's messy enough to apply that logic inside this universe. If I had an apple, but no knowledge of where apples come from, I couldn't say much about the apple's origin. I could look at the stem, and guess that the apple came off of something stemmish, but I couldn't say whether that stemmish thing was a tree or a vine or a bush or a peduncle emerging from the ground.
In conclusion, I'm going to wander around the student union building. Maybe I'll find some Christian evangelists who use arguments from nature to assert belief in God. I would pretend to be convinced by their arguments, then affirm belief in Waheguru of the Sikhs. Do you want to come with me?