Chapter 15 of Groothuis' Christian Apologetics is on the Moral Argument, although it only briefly covers it in one of its sections. It covers much more ground as a nice introduction to Ethics, without going into specific theories (consequentialism, et cetera).
Two Red Herrings
1. Atheists can be moral without believing in God. (Answer: Their morals correspond to nothing without God.)
2. Nontheists use moral terms without referring to God. (Answer: Above.)
Where Dr. Groothuis says "The moral argument...instead addresses the justification of moral claims" (332)--I disagree and think he was right when he said it "addresses the metaphysical foundation of goodness" (331)--aka, the referent (332). Justification/epistemology and metaphysics/ontology are to each other as oughts are to ises, values to facts, and so on. What needs to be justified in Ethics are particular theories (like the Golden Rule). What the Moral Argument does is deal with the metaphysical grounding, or referent (what real being the Golden Rule describes or corresponds to), not the justification of a particular theory.
Ethical relativism "claims that moral judgments are dependent on contingent social and historical arrangements." (332) Cultural relativism "teaches that we should follow the moral principles of our culture." (332) The judgments of our culture are only normative and binding in our own culture, not in another (and vice versa). leads to: [Individual relativism: "Moral judgments and obligations are based entirely on an individual's personal preference." (333) "If there is no objective moral standard, it is left to the individual to decide what is right and wrong." (339)] leads to: [Nihilism: "the denial of objective value of any kind: moral, aesthetic, intellectual and so on. Nihilism asserts moral meaninglessness." (342-3)]
Dependency thesis: "morality inherently depends on cultural factors and no other factors." (333)
"Differing phonetic, syntactic and semantic elements [between languages] do not render judgments like 'The earth is round' relative to culture. Therefore, if varying nonmoral linguistic affirmations can successfully capture objective reality, so can varying moral affirmations capture--or fail to capture--objective realities." (334)
Diversity thesis: "morality will differ from culture to culture." (334)
1. Disagreement does not mean there are no right answers.
2. There is cross-cultural agreement on fundamental human values.
Which culture decides morality?
Reformer's dilemma: "moral reformers should be condemned as cultural and moral deviants...deemed immoral when judged by the extant standards of their societies." (337)
Progress, tolerance and relativism.
"All we can claim is that cultures change with respect to their moral evaluations" (338) --since they are only normative for that culture.
Inconsistent: NEVER be intolerant, ABSOLUTELY absolutism is wrong, EVERYONE should be tolerant, ALWAYS be tolerant.
Moral horror: NEVER be intolerant is placed higher than NEVER torture, NEVER rape, NEVER mutilate genitalia.
Leads to individual relativism, which leads to nihilism, which is unlivable.
The Argument from Damnation
Some acts are so desperately wicked, they demand a punishment greater than the world has to offer. It calls out for supernatural justice against a backdrop of unconditional goodness.
Atheism and the denial of objective moral value:
"Morality thus reduces to physical and biological factors simply because this is all that exists. There is no independent sphere for moral realities that transcend the merely physical and cultural." (349)
Russell, Ruse, Nietzsche, Sartre (agreeing with Dostoevsky, a Christian, that "If God didn't exist, everything would be possible"), Leff are discussed to support the above quote.
These are not tied back to cultural/individual relativism for some reason: Descriptivism merely describes the sovereign-made laws people follo, personalism sets up the individual as sovereign, and majoritarianism sets up the majority as sovereign--but "the majority opinion should set the law" (353) would have to be the first law that has to be taken as granted, outside the majority system. All possible sources of evaluations are subject to "the cosmic 'sez who'" (354) objection. I remember this from Tim Keller's "The Reason for God". Leff cries out to a God he denies.
(I shrunk three arguments together...)
1a. If pantheism is true, then there are no objective moral values, either because (a) it overtly denies them, or (b) it vainly attempts to affirm and deny them on the basis of the two-level view of truth.
1b. Either God exists (as the "final evaluator") or nihilism is true (all evaluations arbitrary).
1c. If a personal God does not exist, then objective moral values do not exist.
2. (Nihilism is false because...) There are objective moral values (established above).
3. Therefore, pantheism is false (a personal God exists).
My thoughts on the moral argument.
At first it looks as if Dr. Groothuis is setting up a voluntaristic view of God. That is the view of strict Divine Command Theory--whatever God says, goes. He "creates" the good. But--in reality--he was just setting up for the Euthyphro Dilemma, and then resolves it with essentialism--that God commands in accordance with his character.
Euthyphro dilemma: "(1) If something is good because God wills it good, God could will anything (even murder), and it would be, ipso facto, good. But this is absurd. (2) If God's will is not the source of good, goodness lies outside God's being and this robs him of his moral supremacy (an essential attribute of deity)." (356)
Resolution: "God's moral will is based on God's changeless nature. ...Objective moral values, according to the Bible, are not created... Just as God does not create himself. ... To hearken back to Leff, to say that God's moral utterances are 'performative' does not mean that God brings something into being at a particular time that did not exist previously--...he is speaking according to the eternal nature of his being." (356)
Are moral values brute facts?
Atheistic moral realism: Objective moral values are brute facts not related to God.
1. Truth is that which corresponds to reality. To what being do an atheist's moral facts correspond?
2. Hastings Rashdall: "Only if we believe in the existence of a Mind for which the true moral ideal is already in some sense real, a mind which is the source of whatever is true in our own moral judgments, can we rationally think of the moral ideal as no less real than the world itself. ... A moral ideal can exist only in a Mind from which all Reality is derived. Our moral ideal can only claim objective validity in so far as it can rationally be regarded as the revelation of a moral ideal eternally existing in the mind of God." (358-9)
3. On atheism, there is no overall design that applies to humans. The brute facts are ex nihilo...
4. How can moral values be brute facts about people--before people--on materialism? [My thoughts: It's kind of like photosynthesis, before photosynthesis...it wasn't true until photosynthesis happened...and if photosynthesis had never happened, it never would have been true. But there isn't even an always-good (non-divine) human to which moral facts can be true.]
5. Says who? (not obligated) (I feel it is the joy and satisfaction that motivates us...not just God saying so.)
6. There are no real rights, no real "high" view of human nature.
7. If moral truths are true in every possible world ("necessary"), there must be a (necessary) being to which they are true in every possible world (see 1 and 2).
The God-Haunted Conscience
"Our consciences reveal both a transcendent goodness and our own violation of this goodness through our pettiness, theft, cruelty, dishonesty, lust and a hundred other minor and major infractions. C.S. Lewis ends his moral argument for God in Mere Christianity by alerting the reader that Christianity has nothing to say to people 'who do not know they have done anything to repent of and who do not feel that they need any forgiveness.' // 'It is after you have realized that there is a Moral Law and a Power behind the law, and that you have broken that law and put yourself wrong with that Power--it is after all this, and not a moment sooner, that Christianity begins to talk.'" (363)