Defenses of the Moral Argument for God’s Existence

The moral argument is an important one to many theists who wish to rationally justify belief in God to unbelievers or those questioning whether or not God exists. The argument is presented as follows:

P1: If God does not exist then objective moral values do not exist.
P2: Objective moral values do exist
P3: Therefore, God exists.

We will examine arguments that theists have forwarded to support this. We will also look at common arguments critics have offered against it.

First, it is important to acknowledge that the moral argument is logically valid. This does not mean that the argument is true or compelling, rather it just means that it is deductive and the conclusion is inescapable if the premises are true. What critics must then do is dispute one of the premises to avoid the conclusion that God exists. What are some of these arguments?

Many critics argue that unbelievers can be moral or live moral lives and that this undermines the moral argument for God’s existence. But defenders answer this by responding that the moral argument argues for God’s existence and has nothing to do with anyone’s belief in God. In other words, the objection is formulated on a misunderstanding. The moral argument does not claim that persons (whether atheist, agnostic, or secular) cannot be moral if they do not hold to belief in God. Instead, it argues that if God does not exist then there can be no basis for objective morality. The argument also holds that there must be some transcendent standard or standard beyond the subjective opinions of human beings for there to be objective morality. This can only be found in God. Only if God exists can P2 to the argument be true, namely that there do exist objective moral values. 

Second, there is the challenge of providing evidence for P2 to affirm that objective moral values do exist. One way proof of P2 has been offered is based on our acceptance of the reality of the external world of objects beyond our mind for this seems reasonable even though we cannot prove it. We believe in the external world based on our experience of the world. From this, it follows that we are justified in believing that the external world is real unless we had good evidence to think otherwise. In the absence of defeating evidence for our belief in an external world, we are justified in trusting our experience of the external world. This is paralleled to the moral argument. Although there is no way to empirically prove that objective moral values exist, we can affirm them based on our experience of the world. Like belief in an external world, we are justified in believing in objective moral values in the absence of a defeater. By moral experience of the world, one means that we experience the world in such a way that we know certain behaviors are objectively evil or good. It is objectively good to donate food and money to reliable charities. It is objectively evil to commit genocide on the elderly, men, women, and children to expand one’s territory. These just seem (feel) obvious based on our experience of the world. According to theist philosopher William Lane Craig,

“My claim is that we are justified in believing (2) on the ground of our moral experience unless and until we have a defeater of that experience, just as we are justified in believing that there is a world of physical objects around us on the ground of our sense experience unless and until we have a defeater of that experience. Such a defeater would have to show not merely that our moral experience is fallible or defeasible but that it is utterly unreliable, that we may apprehend no objective moral values or duties whatsoever. Our moral experience is so powerful, however, that such a defeater would have to be incredibly powerful in order to overcome our experience” (1).

It then follows, argues the theist, that we have strong proof for P2. Further, as the twentieth-century Christian apologist C. S. Lewis also remarked, even the “man who says he doesn’t believe in a real Right and Wrong, you will find the same man going back on this a moment later.” In other words, we not only believe in objective moral values based on our experience of the world, but we also cannot help but act as if moral values do exist.

Skeptics have sometimes pointed to all the evil in the world as a disproof of the argument. But if we examine this closely it is also based on a misunderstanding, although the argument is relevant to other skeptical arguments from theodicy. It is important to look at the moral argument and see which premise is brought in question by an objection. The argument from there being evil in the world does not challenge any premise and is therefore unable to disprove the argument itself. But theists are also quick to use this objection to strengthen the moral argument. They argue that it affirms P2 because one needs to affirm that objective moral values exist to make the argument from the evil in the world. If objective moral values do not exist, then it makes no sense to argue from there being evil in the world. Theists like to quote C. S. Lewis on this point because he helpfully recognized this point,

“My argument against God was that the universe seemed so cruel and unjust. But how had I got this idea of just and unjust? A man does not call a line crooked unless he has some idea of a straight line. What was I comparing this universe with when I called it unjust?… Of course I could have given up my idea of justice by saying it was nothing but a private idea of my own. But if I did that, then my argument against God collapsed too–for the argument depended on saying the world was really unjust, not simply that it did not happen to please my fancies. Thus, in the very act of trying to prove that God did not exist – in other words, that the whole of reality was senseless – I found I was forced to assume that one part of reality – namely my idea of justice – was full of sense. If the whole universe has no meaning, we should never have found out that it has no meaning: just as, if there were no light in the universe and therefore no creatures with eyes, we should never have known it was dark. Dark would be without meaning.”

It was based on the moral argument that Lewis became convinced of the truth of theism and converted as a result.

A third argument against objective moral values is that if morality is objective, then why do some cultures engage in immoral practices like cannibalism, female genital mutilation, infanticide, and so on? But this seems to be the same argument we just examined based on there being evil in the world. The critic here is pointing to evil practices in the world that he or she condemns for their objectively evil nature. But to do so is to affirm P2 to the moral argument, namely that objective moral values exist. It then follows that God exists (P3). 

Another point to be made here is that these immoral acts also affirm objective moral values because the cultures in question are performing acts that they deem to be objectively morally good. In other words, they affirm P2 to the argument. We just don’t agree that these acts are morally good because today we believe killing infants and female genetical mutilation are objective evils. For example, in some migrating pre-historical hunter-gather tribes it was not uncommon for members of the tribe to kill off their elderly. The elderly slowed the tribe down which proved a threat to their survival. What was the objectively morally right thing to do in this situation? According to the tribe, the morally right action is to club the elderly member over the head while they are not looking. Such an act, which we find immoral today, affirmed objective moral values because the survival of the tribe was a moral virtue.

Fourth, there is the challenge from evolution and social conditioning. The argument here is that human beings believe that moral values exist because this is the way they evolved. Human evolution over the past two hundred thousand years conditioned persons to believe this. Just as a troop of baboons evolved mutually beneficial behavior, so have human beings evolved behavior that is mutually beneficial. In fact, if we rewound human evolution, we could have evolved an entirely different notion of morality. This demonstrates, argues the critic, the subjective nature of morals derived from evolution and social conditioning. 

How have theists responded? Some have argued that just as we evolved to experience the external world, we also evolved to experience objective moral values. The evolutionary conditioning of human cognitive faculties does nothing to prove that the external world does not exist. In fact, we evolved a conscious awareness of the external world because it really does exist. Similarly, we evolved a notion of objective moral values because objective moral values do exist. On such a view, objective moral values could have been gradually discovered during the course of human evolution.

Moreover, theists also argue that to claim that objective moral values and duties do not exist because of the evolutionary process is to commit the genetic fallacy. This fallacy attempts to explain away a belief by how it originated. Even if human beings evolved their experience of moral values, this does nothing to say that objective moral values do not exist in reality. It just shows how humans came to know moral values.

But what about P1 to the argument? We haven’t said much about P1 yet, but this is informative because critics of the moral argument generally accept P1 to be true (most of the objections, as we have seen, attempt to defeat P2). It is accepted that only if God exists can objective moral values exist. This is because God provides that transcendent moral standard over and above human beings. So, if God exists, we are not dependent on subjective human belief or culture about what is good or evil. Without God, we are left to our own devices to invent morals by which to live.


  1. Craig, William Lane. 2015. #449 Are We Justified in Believing in Objective Moral Values and Duties? Available.

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