Theists often offer the moral argument in support of God’s existence.  While the argument can take many forms, the essence of the argument is that objective moral values exist, and are best explained by the existence of a transcendent, personal being whose very nature is good.  The common response offered by atheists is that one need not believe in God to be moral and loving.  “After all,” they say, “I am a moral person and I don’t believe in God.  Surely, then, belief in God is not necessary for morality.”

There are two things amiss about this response.  First, it misconstrues the theist’s argument.  He is not arguing that one must believe in God to recognize moral truths (a claim about moral epistemology) or to behave morally, but rather that God must exist for there to even be such a thing as morality (a claim about moral ontology).  God’s existence is necessary to ground moral values in objective reality.  If there is no God, there can be no such thing as objective moral values.  We might choose to call certain behaviors “good” and certain behaviors “evil,” but such ascriptions are subjective determinations by human communities; i.e. they merely describe the beliefs and preferences of human subjects, not some object that exists transcendent to them.