It is quite often argued by proponents of the Abrahamic faiths that god, whichever god it is, is the ultimate and inviolate source of humanity and that somehow the existence of our conscience, our guilt when we do bad things, is evidence for this god.
Needless to say there are problems with this.
- The god described in their holy books is a capricious, violent, hypocritical fuckwit of the first order. Dawkins puts it more poetically but you can find his description for yourselves here “The God Delusion“. Suffice to say if you’re looking for a perfect moral guide a mass-murdering torturer and engineer of genocide isn’t a safe bet.
- Morality does change, it’s subjective. One can see that even through the books. Christians would even argue themselves that the New Testament overrides the old (even though it explicitly says it doesn’t) but to argue that moral systems can change is to argue that god is not all knowing or perfect since otherwise he’d have gotten it right first time. Different cultures, different times, different morals. This is particularly difficult for Muslims since Mohammed was, by any remotely modern standard, a kiddie fiddler. Try asking them if screwing children is wrong and, well… see what happens. Morality is also situational, stealing to feed a starving child would – for example – be considered good.
- Our conscience can enforce any moral system with which we’re ‘programmed’. While certain very broad and general moral rules seem to apply across humanity these are extremely basic and can be accounted for through evolutionary psychology and our existence as a social species (altruism good, selfishness bad). Whatever morality you’re brought up into, otherwise, will determine what you feel good, bad or indifferent about.