A common charge by non-believers is that Christian Ethics suffers from the naturalistic fallacy, but that has some issues.
Hume’s argument, you may recall, was that “you cannot deduce ‘ought’ from ‘is.’” That is, you cannot derive normative conclusions from merely descriptive premises. G. E. Moore used the phrase “naturalistic fallacy” to describe that kind of error. Now in a Christian epistemology, matters are not quite so simple. The reason is that God is both the chief fact and the chief norm. To put it differently: God’s existence is a fact, and he is a person who rightly makes the highest demands on our obedience. Thus he is at the same time the most significant fact of our experience and the highest norm for our lives. For this reason, Christians may often seem to be reasoning from description to norm. “God commands x, therefore I must do x.” Is that a naturalistic fallacy? No, because we are not passing from a merely descriptive premise to a normative conclusion. Because God’s commands are supremely normative, the self-expression of God’s supremely normative nature, they entail normative conclusions. As another example, consider the New Testament’s argument from indicative to imperative, as in Col. 3:1, which may be formulated logically: “You are risen with Christ; therefore you must seek the things that are above.”2 Is that a naturalistic fallacy? No again. To be risen with Christ is both a descriptive and a normative reality. Those who are risen with him are elevated with him, in him, to positions of honor and responsibility. Among those responsibilities is the obligation to seek what is above.
Christians metaphysics is quite different from atheistic ethics. Atheists are left with impersonality being ultimate in their universe while in a Christian Model of reality it is ultimately personal. But God isn’t like facts in an atheist worldview. He is a person and a supremely perfect normative person.