Someone did a blog with the above title and I gave this response:
I think our brains are just modular. Our minds work more like a democracy than a dictatorship, different conflicting impulses constantly competing for our actions. Your christian friend committed adultery for the same reason someone eats a twinky – she wanted to. And she then tried to fix her marriage for the same reason that person will then go exercise and try to eat better – she wanted to do that too.
We can want opposite things, our rational mind is what tries to govern our emotions and impulses and decide what’s best for us. Some people choose to personify parts of themselves and call them god or the devil. In psychology this is called externalization, and it is often either to avoid guilt or shame (“the devil/demon made me do it”) or to allow a broken down person with zero self confidence to have confidence in their wisdom, actions, or decisions by believing they come from someone they can have confidence in – god.
Unfortunately if we’re not careful this can be dangerous – it can for instance give cover to some really crappy impulses, if the person’s a bigot and they externalize their shitty views about minorities and believe they come from god for instance that just makes them all the less able to be reasoned with – after all how dare you question GOD!? Whereas if it were just their own opinion it might be easier to get them to admit it at least could, hypothetically, be wrong.
Another problem is that in order to externalize your sense of right and wrong you need to use something… external. Like the bible. You may not see this as a downside but I, having read much of the thing (and not just the cuddly bits) and having seen the atrocities justified by scripture, do see it as a downside. Scripture says many wonderful things and many terrible things and can be invoked just as easily to justify both.