The cornerstone of the moral argument is the existence of an objective moral standard. If there really is a standard of right and wrong that holds true regardless of our opinions and emotions, then the moral argument has the ability to convince. However, apart from the existence of such an objective standard, moral arguments for God’s existence (and Christian theism) quickly lose their persuasive power and morality as a whole falls to the realm of subjective preference. Although I could say a fair amount about what the world would be like if morality really was a matter of preference (consider The Purge), the purpose of this article is to provide reasons for believing in objective morality (or “moral realism,” as philosophers call it).
Because of his continued focus on the objective nature of morality throughout his writings, and due to his unique ability to communicate and defend this concept in a clear and compelling manner, I will rely heavily on the thought of C. S. Lewis below. As I’ve read through a number of Lewis’s books, I’ve identified eight arguments he raises in favor of objective morality. Below is my attempt to list these eight arguments and offer a few thoughts of my own concerning each.
1) Quarreling between two or more individuals.  When quarreling occurs, individuals assume there is an objective standard of right and wrong, of which each person is aware and one has broken. Why quarrel if no objective standard exists?
By definition, quarreling (or arguing) involves trying to show another person that he is in the wrong. And as Lewis indicates, there is no point in trying to do that unless there is some sort of agreement as to what right and wrong actually are, just like there is no sense in saying a football player has committed a foul if there is no agreement about the rules of football. 
2) It’s obvious that an objective moral standard exists.  Throughout history, mankind has generally agreed that “the human idea of decent behavior [is] obvious to everyone.”  For example, it’s obvious (or self-evident) that torturing a child for fun is morally reprehensible.
As the father of two children, a daughter who is five and a son who is three, I have noticed that even my young children recognize that certain things are obviously right or wrong. For example, while watching a show like PJ Masks, my children can easily point out the good characters as well as the bad ones – even without my help. In short, the overwhelming obviousness that certain acts are clearly right or wrong indicates that an objective moral standard exists.
3) Mistreatment.  One might say he does not believe in objective morality, however, the moment he is mistreated he will react as if such a standard exists. When one denies the existence of an objective standard of behavior, the moment he is mistreated, “he will be complaining ‘It’s not fair!’ before you can say Jack Robinson.” 
Sean McDowell relays an example of this when he shares a story involving J. P. Moreland taking the stereo of a University of Vermont student who denied the existence of objective morality in favor of moral relativism. As Moreland was sharing the gospel with the university student, the student responded by saying he (Moreland) couldn’t force his views on others because “everything is relative.” Following this claim, in an effort to reveal what the student really believed about moral issues, Moreland picked up the student’s stereo from his dorm room and began to walk down the hallway, when the student suddenly shouted, “Hey, what are you doing? You can’t do that!” 
Again, one might deny the existence of an objective standard of behavior through his words or actions, but he will always reveal what he really believes through his reactions when mistreated. (Note: Here at moralapologetics.com, we do not recommend you go around and mistreat others, as that wouldn’t be a moral way to do apologetics. See what I did there? Rather, we are simply bringing up the mistreatment issue as a way of exposing a deep flaw within moral relativism.)
4) Measuring value systems.  When an individual states that one value system is better than another, or attempts to replace a particular value system with a better one, he assumes there is an objective standard of judgment. This objective standard of judgment, which is different from either value system, helps one conclude that one value system conforms more closely to the moral standard than another. Without some sort of objective measuring stick for value systems, there is no way to conclude that civilized morality, where humans treat one another with dignity and respect, is better than savage morality, where humans brutally murder others, even within their own tribe at times, for various reasons.
To illustrate this point, Lewis says, “The reason why your idea of New York can be truer or less true than mine is that New York is a real place, existing quite apart from what either of us thinks. If when each of us said ‘New York’ each means merely ‘The town I am imagining in my own head,’ how could one of us have truer ideas than the other? There would be no question of truth or falsehood at all.”  In the same way, if there is no objective moral standard, then there is no sense in saying that any one value system has ever been morally good or morally bad, or morally superior or inferior to other value systems.
5) Attempting to improve morally.  Certainly, countless individuals attempt to improve themselves morally on a daily basis. No sane person wakes up and declares, “My goal is to become more immoral today!”  If there is no absolute standard of good which exists, then talk of moral improvement is nonsensical and actual moral progress is impossible. If no ultimate standard of right and wrong exists, then one might change his actions, but he can never improve his morality.
If there is hope of moral improvement, then there must be some sort of absolute standard of good that exists above and outside the process of improvement. In other words, there must be a target for humans to aim their moral efforts at and also a ruler by which to measure moral progress. Without an objective moral standard of behavior, then “[t]here is no sense in talking of ‘becoming better’ if better means simply ‘what we are becoming’ – it is like congratulating yourself on reaching your destination and defining destination as ‘the place you have reached.’” 
6) Reasoning over moral issues.  When men reason over moral issues, it is assumed there is an objective standard of right and wrong. If there is no objective standard, then reasoning over moral issues is on the same level as one arguing with his friends about the best flavor of ice cream at the local parlor (“I prefer this” and “I don’t like that”). In short, a world where morality is a matter of preference makes it impossible to have meaningful conversations over issues like adultery, sexuality, abortion, immigration, drugs, bullying, stealing, and so on.
7) Feeling a sense of obligation over moral matters.  The words “ought” and “ought not” imply the existence of an objective moral law that mankind recognizes and feels obligated to follow. Virtually all humans would agree that one ought to try to save the life of a drowning child and that one ought not kill innocent people for sheer entertainment. It is also perfectly intelligible to believe that humans are morally obligated to possess (or acquire) traits such as compassion, mercifulness, generosity, and courage. 
8) Making excuses for not behaving appropriately.  If one does not believe in an objective standard of behavior, then why should he become anxious to make excuses for how he behaved in a given circumstance? Why doesn’t he just go on with his life without defending himself? After all, a man doesn’t have to defend himself if there is no standard for him to fall short of or altogether break. Lewis maintains, “The truth is, we believe in decency so much – we feel the Rule of Law pressing on us so – that we cannot bear to face the fact that we are breaking it, and consequently we try to shift the responsibility.” 
Although the eight reasons provided above do not cover all of the reasons for believing in objective morality, it is a starting point nonetheless. If any of the reasons above for believing in objective morality are valid, then the moral argument for God’s existence (and Christian theism) has the ability to get off the ground. In fact, if there are any good reasons (in this article or beyond it) for believing in an objective moral standard, then I think God’s existence becomes the best possible explanation for morality since such a standard at the least requires a transcendent, good, and personal source – which sounds a lot like the God of Christian theism.
 C. S. Lewis, Mere Christianity (New York, NY: HarperCollins, 2001), 3.
 Ibid., 4.
 Ibid., 5.
 Ibid. In the appendix section of The Abolition of Man, Lewis provides a list that illustrates the points of agreement amongst various civilizations throughout history. See C. S. Lewis, The Abolition of Man (New York, NY: HarperCollins, 2001), 83-101.
 Ibid., 6.
 Sean McDowell, Ethix: Being Bold in a Whatever World (Nashville, TN: B&H Books, 2006), 45-46.
 C. S. Lewis, The Abolition of Man (New York, NY: HarperCollins, 2001), 43, 73. Also see Lewis, Mere Christianity, 13.
 Lewis, Mere Christianity, 13-14.
 C. S. Lewis, “Evil and God,” in God in the Dock, ed. Walter Hooper (Grand Rapids, MI: Wm. B. Eerdmans, 2014), 3-4.
 Even if someone’s goal is to become more immoral, he still needs an objective standard to measure the level of his badness.
 C. S. Lewis, Miracles (New York, NY: HarperCollins, 2001), 54.
 C. S. Lewis, The Problem of Pain (New York, NY: HarperCollins, 2001), 10.
 C. Stephen Evans, God and Moral Obligation (New York, NY: Oxford University Press), 2-3.
 Lewis, Mere Christianity, 8.
*About the Author: Stephen S. Jordan currently serves as a high school Bible teacher at Liberty Christian Academy. He is also a Bible teacher, curriculum developer, and curriculum editor at Liberty University Online Academy, as well as a PhD student at Liberty University. He and his wife, along with their two children and German shepherd, reside in Goode, Virginia. This article first appeared on January 18, 2019 at moral apologetics.com