Why theism is necessary and sufficient to ground objective moral obligations

There would be no such a thing as right and wrong, good and evil, virtue and vice, etc. if there were no God. The reason, basically, is because morality is prescriptive. It makes demands on our behavior. A blind and indifferent universe can't make demands on your behavior. Only a sentient authority can. If there is no sovereign authority over and above humanity, then any rules we had to live by would be rules we came up with ourselves and would be free to change if we wanted to. We do have civil laws, but all of these laws depend on authorities. Governments impose laws on citizens. Parents impose rules on children. Morality resembles these laws in the sense that they are prescriptive. But if morality is objective--meaning it exists independently of human preference, desire, sentiment, etc.--then it must originate from an authority that transcends humanity.

Morality is the law above all other laws. It's what allows us to say that a civil law or a rule that somebody gives us is immoral. For example, if your parent told you to kill your brother, you'd have a moral obligation to disobey your parent. If a government passed a law saying that you must sacrifice your parents when they reach the age of 60, that would be an immoral and unjust law that we would have a moral obligation to disobey. Since morality is the law above all human laws, it must originate in transcendent authority.

It's hard to imagine what kind of authority would be sufficient to ground morality, but another contingent being like ourselves wouldn't do the trick. No human, regardless of rank or status, would be sufficient to ground morality. No conceivable alien will do either.

But something like a God would. Imagine a being that was absolutely autonomous. It wasn't beholden to any other authority. It had no peers. It was at the absolutely peak of all authoritative hierarchies.

And imagine a being that is the source of everything else that exists. The being itself doesn't owe its existence to anything else, but everything else owes its existence to this being.

This would seem to be a sufficient source of morality. And it's hard to think of anything less that would suffice. So it seems to me that if such a being does not exist, then there can't be any objective morality.

There can still be *subjective* morality and moral *relativism*, though.

For more on this subject, check out:

If there is no God, then there are no objective moral values.

Does anything really matter?

The divine command theory