Morality, Therefore God: An Evangelistic Strategy


Sarah C. Geis

Article ID:



Aug 27, 2023


May 2, 2017

This article first appeared in the Effective Evangelism column of the Christian Research Journal, volume 38, number 02 (2015). The full text of this article in PDF format can be obtained by clicking here. For more information about the Christian Research Journal, click here.


Humans may disagree on what behaviors are moral, or on the best way to make specific moral decisions. Even so, our fundamental concept of goodness has to come from somewhere. This is what the moral argument for the existence of God addresses. Put simply, morality exists; therefore, God exists. For a culture intoxicated by naturalism, morality provides a strong reason to believe in a Creator—the prerequisite for belief in the person and work of Jesus Christ. For many Christians, the moral argument can serve as an apologetic starting point for evangelization.

To begin, we must understand a key term: objective. For anything to exist objectively means that it exists whether or not anyone believes in it. The law of gravity is an objective fact. It holds true for everyone and cannot be changed even if every human on earth sincerely believed it was false. Christians can learn to help unbelieving souls recognize the existence of objective moral facts (the term I will use to encompass both moral values and duties) and then show that God is the best explanation of those facts.

Christian philosopher William Lane Craig has extensively debated and written on this argument. He presents it this way:

(1) If God does not exist, objective moral values do not exist.

(2) Objective moral values do exist.

(3) Therefore, God exists.1

The reasoning is powerful. Logically, if premises (1) and (2) are true, the conclusion that God exists must also be true. However, if either premise is false, then the argument fails. When we present this argument to non-Christians, we will encounter at least one of the following objections: most will deny the existence of objective morality (rejecting premise 2), but some may claim that objective morality exists without God (rejecting premise 1).

Do Moral Facts Really Exist? There are two ways of explaining the relationship of morality to human beings. Either human beings create their own morality (moral relativism) or they do not (moral objectivism). Relativists hold that morality is determined by individuals (subjectivism) or determined by cultures (cultural relativism). If moral relativism fails, then objective moral facts exist. We can refute relativism by showing that it cannot explain morality without absurdity.

According to individual relativism, whatever an individual approves of is right. This would hold even in the case of contradictory moral beliefs. For instance, if Sally believes that shoving strangers into oncoming traffic is perfectly justifiable, then it is right. But if Billy believes that shoving strangers into oncoming traffic is entirely unjustifiable, then doing so is wrong. So on this view, shoving innocent bystanders into oncoming traffic is both right and wrong at the same time in the same respect. This is logically and existentially objectionable.

But the irrationality of individual relativism gets worse still. There are supposedly no objective moral facts, yet the view itself appeals to an objective concept of rightness when it claims that it is right and other theories are wrong. Put differently, one must make an objective moral statement in order to claim that personal preferences determine right and wrong. Therefore, individual relativism is self-refuting and absurd.

Even though cultural relativism is more popular, it fares no better than its ill-fated subjectivist relative. First, if each culture gets to determine its own morality, then there can be no such thing as a moral reformer. In order for someone to reform his or her culture, the reformer must appeal to a standard outside that culture. The great abolitionist William Wilberforce did just that when he fought to end slavery in Britain. He appealed to the intrinsic value of all people, which his culture largely denied. To the cultural relativist, a would-be moral reformer is just a moral rebel, because the culture determines what is right. Additionally, Martin Luther King, Jr., was only rebelling and not reforming. Worse yet, within Nazi Germany Adolf Hitler would have to be considered more moral than Martin Luther King, Jr., because Hitler was more consistent with his culture’s moral code than was King.

Second, cultural relativism fails to delineate clear cultural boundaries for determining morality. What do we do about subcultures and dual membership in different cultures? When we must decide how we should believe and act, it can be impossible to determine the right culture to follow. The only clear option is to follow the morality of the individual, which we have already shown to be absurd. So, both kinds of relativism fail as plausible alternatives to objective morality.

There are other ways to argue for the existence of objective moral facts. If we can find cross-cultural, universally binding moral standards, this is enormously consequential. For then we can reasonably infer that moral standards exist above and beyond those cultures. In the appendix to the Abolition of Man, C. S. Lewis lists many common values and duties that span all of history and culture. One particularly fascinating example is the cross-cultural duty to care for parents, elders, or ancestors.2 Another universal value Lewis observed is the recognition that justice is better than injustice. Based on these and many more examples, it is reasonable to affirm that all cultures value general moral goodness over evil, even if they might disagree over what good and evil might specifically look like. Different cultures are morally able to assess and judge each other because of this shared concept of good and evil.

So far we have shown that moral relativism in either form is not a tenable alternative to objective morality. Thus the only reasonable approach here is to affirm that objective moral values and duties do, in fact, exist. If they do exist, we must ask what sort of things they are, and where they come from. The logical basis for a moral law is a moral lawgiver, but this too needs to be defended to one yet to be convinced.

God Is the Best Explanation. Objective moral facts exist and must have come from somewhere. In the eighteenth century, the philosopher Gottfried Leibniz articulated what he called the principle of sufficient reason. The principle states that everything that exists has a sufficient explanation of its existence. This can be illustrated by imagining the spontaneous appearance of a purple elephant hovering in the sky above bewildered onlookers. Upon hearing plausible explanations for the flying purple elephant’s appearance, no reasonable person would then reject any hypothesis in favor of no explanation at all. But atheists do just this when they affirm the existence of objective moral facts, yet deny the only legitimate explanation: God. To this atheistic moral realist, moral facts are just there, and need no explanation. This fails as a reasonable option according to the principle of sufficient reason, and should thus be rejected. Now the task of the truth-seeker is to sift through arguments until we find the best explanation for objective morality. 

The Euthyphro dilemma. For millennia, people have been interested in the metaphysical origin of morality. In Plato’s Euthyphro dialog, Socrates presents an apparent dilemma. The problem is often formulated this way: Is a moral choice right because God commands it, or does God command it because it is right? The “Euthyphro dilemma” is often used by atheist and agnostic thinkers as a way to force the theist into making a crushing choice. First, if a decision is morally right simply because God commands that it be so, then morality is entirely arbitrary. God could have just as easily willed rape and murder to be right. Surely the reasonable theist cannot accept this. The second option, however, fares no better. To say that God commands a moral choice because it is right implies that the moral law stands above and beyond God. But this cannot be so, or else God would not be the supreme and ultimate power at all. Many atheists and agnostics claim that since both options are unacceptable, we should abandon all talk of God as the source of morality. What then is the poor theist to do?

The situation is not as dire as it initially seems. The Euthyphro dilemma is not truly a dilemma, but is a trilemma. There is a third option, one that is perfectly coherent and does not conflict with the revelation of God in Scripture. God does issue moral commands, but His reasons are far from arbitrary. He commands what He does because He is good. His own nature, His character, is the standard and seat of goodness itself. The commands of God cannot be changed any more than His essence can be changed (Heb. 13:8). Moreover, this third option has much more explanatory power than positing separately existent objective moral facts that have no explanation of their existence whatsoever.

But there is more. Objective morality consists of both principles and duties. We can easily articulate moral principles such as killing the innocent for pleasure is harmful to society. But we cannot as easily account for why we should follow those principles. Why should we care about society or about human well-being? Even if the nontheist is correct that objective moral facts exist without God, our sense of obligation must be explained. Those impersonal, immaterial moral facts, whatever they would be, could not compel us to follow them. Furthermore, we cannot attribute these duties to survival instincts, because duties often go directly against those instincts. The unguided process of natural selection is an inadequate explanation, so there must be a better one. The commands of an omniscient, omnipotent, omnibenevolent God perfectly account for our sense of moral obligation.

According to our brief analysis, God is the source, or ground, of objective moral facts. On the other hand, the belief in separately existent objective moral facts is an irrational leap of blind faith. Without God, objective morality would not exist. With God, objective morality finds its roots. May we lovingly help a lost world to seek these truths and find God.

Sarah C. Geis teaches philosophy and apologetics at Denver Seminary, and is the associate director of the Gordon Lewis Center for Christian Thought and Culture. She also teaches undergraduate philosophy classes at the Community College of Aurora.



  1. William Lane Craig and Walter Sinnott-Armstrong, God? A Debate between a Christian and an Atheist (New York: Oxford University Press, 2004), 19.
  2. C. S. Lewis, The Abolition of Man (New York: HarperCollins, 2001), 90.


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