By Arthur Kettelhut
In Mere Christianity, C. S. Lewis makes the moral argument for God’s existence by giving us examples of everyday encounters with our standards of behavior. Especially the standard of conduct that we expect from other people. These examples show our universal sense of right and wrong, which begs the question: Where does this sense of morality find its source? The moral argument for God’s existence is not the only or strongest one that the apologist can use, but it calls on the external source for an explanation.
Lewis makes the distinction clear between a moral choice and a psychological condition. If one is under the influence of a damaged psyche, a just ethical decision can escape them. The consideration for a decision to be sinful must be under the requisite sound state of mind. We are often told not to judge others based on past actions. But one must factor in the conditions around the decision as well. Lewis refers to the small “central self” which one navigates either toward God or Hell, and the mark that our decisions leave on that self can be profound regardless of their size.
Once one establishes a moral decision, we must reference its objectivity if its meaning is to have any proper definition. Lewis uses the argument from morality to prove his case. This argument has two premises. If objective moral values exist, then God exists, and that objective moral values exist. If both premises are true, then God exists. The first premise is valid, as all humans have a sense of morality in common that is not subjective. When one argues or reasons on a moral point in society, we share an unspoken view of the position on many critical issues, such as it is never good to torture children for fun. These shared views all point to an external source for our morals, which find no explanation in other sources such as social evolutionary conditions. It is also the case that the moral argument stands valid for eternal objective standards for life, but other apologist arguments, such as logic and mathematics, call on the same objective source. We must recognize an external source of morality that can only be explained by a being whose nature is moral—the nature of a personal God.
Without this external objective moral standard, there is only a subjective personal interpretation of morality. Such a state of affairs, if accurate and consistent, would lead to chaos and rampant immorality. What makes Lewis’ determination unique in presenting the moral argument is the personal nature of the Christian God. Our common ethical standards are private to our needs and promote well-being among individuals and communities, something best reasoned by a moral, personal God. And a personal, knowable God who seeks our communion is the best explanation for morals.
Lewis addresses several relationships with regards to how humans relate to each other in a well-functioning manner. The primary association for the individual to maintain is the horizontal one. How we interact and adequately deal with each other is compared by Lewis to being ships at sea.
This analogy serves to illustrate one way the human-machine can go wrong in their voyage. We have to get along to proceed well and build a functioning society. On a personal level, the individual has to hold themselves accountable to a standard of behavior vis-à-vis their daily interactions with others. As Lewis points out, often this relationship is where people most find fault. A sense of fair play and justice, our moral sense, is quickly applied to others when we sense an affront. Paul reminds us of this hypocrisy in Romans 2:1, where he exclaims, “You have no excuse, everyone of you who passes judgment, for, in that which you judge another, you condemn yourself.”
This sense of fair play applies to the community in particular. To function well, we must share a standard set of values found in the objective moral standard. This ethical standard must have a basis in an external unmutable God that the Christian God exemplifies. Of course, what one doesn’t consider immediately is the condition of their inner self. One must check the condition of our internal state and take a moral inventory based on those same objective standards. The external standard must be a transcendental moral value. The author J.W. Wallace uses the extreme example of torturing babies for fun. No sane human would agree that torturing children for fun is acceptable. If objective standards don’t exist, it would be okay to torture for pleasure in some scenarios.
Lewis further extends the analogy of our internal moral inventory to the context of the eternal. We don’t wish to merely behave well and get along with our fellows for this life but must also consider the enormous implications of eternity in our actions. We must give our choices the reverence they deserve.
Only when we possess the alignment between ourselves, our fellow humans, and society can we be able to apply pure moral decisions appropriately. Lewis refers to that moral voice as distinct in Mere Christianity, different from what we know is right and wrong, and separate from our baser animalistic instincts. This moral voice is the eternal morality embedded in the unconscious mind of the thinker.
This moral voice also extends to the societal and cultural levels. Even professional ethicists can have the opinion that morality is not purely subjective. Theodore Schick writes that “Since cultures are not morally infallible–since they can sanction immoral practices–cultural relativism cannot be correct.” Societal norms can be temporary and subjective in precise details regarding morals as applied to social situations. Nothing in this fallen world can offer the constancy that Christian morality can provide. Even though groups may disagree on specific moral actions, this doesn’t prevent an absolute moral standard. The perseverance of an eternal, just God that personally and societally provides our sense of moral direction, a direction that cannot err.
See also: CS Lewis and the Culling of Humanity
 C. S. Lewis, Mere Christianity: A Revised and Amplified Edition, with a New Introduction, of the Three Books, Broadcast Talks, Christian Behaviour, and Beyond Personality, 1st HarperCollins ed. (San Francisco: HarperSanFrancisco, 2001), 91
 J. Wallace, “The Self-Evident Nature Of Objective Moral Truths,” Cold Case Christianity, 2017, accessed July 21, 2021, https://coldcasechristianity.com/writings/the-self-evident-nature-of-objective-moral-truths/.
 Theodore Schick, “Is Morality a Matter of Taste?,” Free Inquiry 18, no. 4 (1998): 32–34, http://ezproxy.liberty.edu/login?qurl=https%3A%2F%2Fwww.proquest.com%2Fmagazines%2Fis-morality-matter-taste%2Fdocview%2F230083555%2Fse-2%3Faccountid%3D12085.