The journey from is to ought without a bridge?

 Atheists Who Scold Us on Morality Unwittingly Acknowledge God’s Existence 

Michael Egnor 

Biologist P. Z. Myers detests challenges to his atheism based on the reality of Objective Moral Law:

There is a common line of attack Christians use in debates with atheists, and I genuinely detest it. It’s to ask the question, “where do your morals come from?” I detest it because it is not a sincere question at all — they don’t care about your answer, they’re just trying to get you to say that you do not accept the authority of a deity, so that they can then declare that you are an evil person because you do not derive your morals from the same source they do, and therefore you are amoral. It is, of course, false to declare that someone with a different morality than yours is amoral, but that doesn’t stop those sleazebags. 

Actually, Christians don’t ask, “Where do your morals come from?” in order to call atheists evil. We do it to point out that objective morality is powerful evidence for God’s existence. 

Subjective and Objective 

How so? From our human perspective, moral law can have two origins — subjective and objective.

Subjective moral law is based on human opinion. It may just be one man’s opinion, or it may be the collective opinion of a group of people. If our standards are wholly subjective, dislike of strawberry ice cream and dislike of genocide are not qualitatively different. The dislike is just human opinion.

Objective moral law, by contrast, is outside of human opinion. It is something that we humans discover. We do not create it. Thus, objective moral law exists beyond mere human opinion.

Now a distinction emerges. Personal preferences (e.g., about ice cream) are qualitatively different from personal opinions about genocide — we oppose genocide because it is objectively wrong, not just because it is not quite to our taste.

Of course, if a value judgement prevails over other human value judgements, there must be Someone whose opinion is Objective Moral Law. There must be a Law-Giver.

Please note that this argument is ontological, not epistemological. It is not an argument about how well we can know what the Moral Law is. It is an argument that Objective Moral Law exists, regardless of how well we can or do know it.