I got into a discussion with a pandeist yesterday, my first ever. I've been fine tuning my arguments against deism for a little bit now, and I was eager to see how they'd work out against a believer.
The thing that became increasingly obvious to me as the discussion went on was that a large part of his arguments were identical in a way to those used by creationists. In his parlance, it was proof of 'purpose' in the universe rather than proof of a creator, but the argument was more or less the same; that the universe is fine tuned for life, and if cosmological constants were slightly different, life couldn't exist, and therefore it all had to be designed.
We all know the arguments against this, I think; first, that the universe has the appearance of design not because it was designed for us, but because we came to be within it, and therefore we had to evolve to suit it, not the other way around. See Douglas Adams' sentient puddle. And secondly, that if the universe were not as it is, we wouldn't be here to see it.
That second part is what I'm focusing on right now. Most often, when I point this out to those I'm debating, it's either scoffed at or ignored. Of course we wouldn't be!, they shout, What does that prove?.
I think there's a nuance to the weak anthropic principle that a lot of people are missing out on. Indeed, they're quite right; it certainly doesn't prove the non-existence of a creator. What it does do is highlight exactly why their idea of a fine-tuned universe is not evidence of a creator.
How's that? Well, the universe is observably suited for life. Nobody argues with this; if gravity was just a little different, planets and suns either wouldn't form, or would form immediately into black holes. If the nuclear forces were a little different, perhaps atoms as we know them wouldn't be able to exist. There's a laundry list of items like these.
But what does this tell us about how the universe was created? Precisely nothing. Imagine two neighboring universes, side-by-side. They're identical in every detail, except that one had an intelligent creator, and one formed from wholly natural events. The cosmological constants happen to be the exact same, and so if you were look at these two universes billions of years into their developments, how would you be able to distinguish between the created one and the natural one?
This is the point, I think, of the whole thing. We can't. Looking out into the depths of space, we see that the universe is suited for life, but how can we tell if it's natural or created? We can't, not just by looking at them. The argument of the fine-tuning of the universe - used by creationists and deists alike - is null. It's not evidence of anything, either way. You can go on forever about how unlikely it is that a universe would form that was exactly suited for life, and I'll keep saying the same thing. If it wasn't, we wouldn't be here to care. That we are here shows only that the universe exists as it does. That's all.
Why, then, would one not believe in a creator? I've just admitted that by the fine-tuning argument, the one is exactly as likely as the other. Simply put, believing so brings nothing to the table that needs to be there. We have naturalistic hypotheses for the origin of the universe as we know it, and we're learning more every day. I see no reason to not to believe that given enough time, these hypotheses will become theories, and we'll actually know how the universe came to be. Such is the history of science; the unknown becomes known with astonishing frequency. To say 'we know how all this happened naturally... but a god kicked it all off' is unnecessary. It's redundant. It's like adding 1 + 1 + 0 to get two. The zero doesn't need to be there. Neither do gods. And given the history of the supernatural - given that every supposed instance of things existing outside of nature has been debunked - I can't see any reason to suppose that the universe has an origin outside of natural law either.
Especially when natural law explains it so very, very well.