I'm not sure what you mean when you say consciousness arose out of nothing. Nor that it has no purpose. As best we can tell, consciousness is an emergent property of brains. The more complex the brain (e.g. fly vs dog) the more self aware the creature is. And I'd also point out that brains are immensely useful. Being able to make sense of our environments and make predictions about the future is hugely beneficial to an animals survival.
More importantly, even if we do presume the existence of a God, I still don't see how that sheds any light on the nature of consciousness except to kick the question back further: Why do god's have consciousness and how did their consciousness arise out of nothing?
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Concerning Rowan Williams' pig analogy, I find it more than a bit problematic. We know a pig's foot print because we have prior experience with pigs feet and their foot prints. And even if we came across an unknown creatures foot prints we could still make educated guesses about that creature by comparing it to other creatures foot prints.
But with gods we have no prior knowledge. We can't tell the difference between God inspired life and non-god inspired life. God created universes and non-god created universes. God formed consciousness and non-god formed consciousness.
If Rowan William's can't tell me what types of legs a creature has - much less if it even has legs - how can we determine what kind of foot print such a creature might leave? If Rowan Williams' can't tell us any aspects or properties of a God - how can we go looking for the effects of such a god?
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Lastly, I'd like to point out that the problem of evil is really only a problem for Christians who claim God is all loving and all powerful. And it's a HUGE problem. One that, rightly for the ages, atheists have been bringing up again and again because it's just so absurd. Saying it's "nothing new" in no way diminishes how utterly devastating this problem is to mainstream Christianity. It'd be a bit like saying "talking about Jupiter's moons orbiting the gas giant is nothing new against geocentricism. The Heliocentric's have been point this out for hundreds of years."
Well yeah! Of course they have! Because it shows how demonstrably false the teachings of the church that the earth was the center of the universe was. Likewise, the problem of evil shows how demonstrably false many Christians belief that an all loving and all powerful god exists is.
(P.S. The Bible saying something is "incomprehensible" in no way excuses it from it's demonstrable falsehoods. Christians don't get to say "God is incomprehensible" therefore humanity really did begin six thousand years ago with Adam and Eve despite the mountains of evidence to the contrary. Or, the sun was formed after the earth - or God is all loving and all powerful - or any other nonsense in the Bible - simply by appealing to the incomprehensible.)