The Moral Argument for God: Why Goodness Needs a Ground

The moral argument is the case for God's existence that reasons from the reality of moral values and duties to God as their only adequate ground. In William Lane Craig's well-known form it runs in three steps: "If God does not exist, objective moral values and duties do not exist." "Objective moral values and duties do exist." "Therefore, God exists." The argument is valid, so the debate turns on its premises. Below we set out the strongest case against the moral argument for God, the standard theistic answers at full strength, and where the Many Beings series lands.

Key takeaways

• The moral argument is about grounding, not knowing. It asks what makes moral truths true, so the fact that atheists know right from wrong leaves it untouched.
• Its hardest rival is secular moral realism, not relativism. The realist grants that morality is objective and denies that it needs any ground.
• Theists answer with divine command theory, natural law or Kant's practical argument. Each secures something real, and each strains at one point.
• Frame-Indexed Classical Theism (FICT) assigns relativism and absolutism to different frames. Where divine command theory grounds duty in commands and secular realism leaves moral facts brute, it holds that our access to the good is partial while the standard itself is God's own nature.

What is the moral argument?

The moral argument names a family of arguments. The Stanford Encyclopedia of Philosophy, in an entry by C. Stephen Evans and David Baggett, says such arguments "form a diverse family of arguments" that "reason from some feature of morality or the moral life to the existence of God." The feature varies: moral obligation, moral knowledge, human dignity, the hope that goodness and happiness will finally meet. Logic textbooks use the same phrase for any argument with a moral conclusion, such as "lying is wrong, so I should not lie." That is a different subject.

Craig's version, the one most readers meet first, turns on the word objective. "By 'objective'," he writes, "I mean 'independent of people's opinions.'" The claim is that some acts would be wrong even if everyone approved of them, and that a fact of that kind needs a ground no human opinion can supply.

The argument has a long history. Thomas Aquinas's fourth way in the Summa Theologiae is its precursor. "The fourth way is taken from the gradation to be found in things," and it ends: "Therefore there must also be something which is to all beings the cause of their being, goodness, and every other perfection; and this we call God." Immanuel Kant gave the argument its modern form. Duty commands us to seek the highest good, and he concluded in the Critique of Practical Reason that "it is morally necessary to assume the existence of God." W. R. Sorley later put it as a syllogism, as Wikipedia records: "If morality is objective and absolute, God must exist." C. S. Lewis brought it to the public in Mere Christianity, which the Stanford entry calls "almost certainly the best-selling book of apologetics in the twentieth century."

Free — the complete book

Get Book 1: Resolving the Free Will Dilemma free when you enter your name and email.

This essay takes one piece of it. Resolving the Free Will Dilemma takes the whole dilemma from first axiom to conclusion — the complete book, free.

No spam. Unsubscribe in one click.

Lewis began from his own complaint against God. The universe seemed cruel and unjust to him, and he asked where he had found the standard by which he judged it. "A man does not call a line crooked unless he has some idea of a straight line." Most people feel the argument's force before they can state it, which is why it stands beside the cosmological and design arguments in any survey of the evidence for God, and why Aquinas' Five Ways count goodness among the marks of the first cause.

If you want the method behind everything that follows, Volume One is free to download.

The strongest case against the moral argument

The strongest case against the moral argument comes from three directions, and the third is the most serious.

The first is error theory, the view that there are no objective moral values at all. J. L. Mackie is its best-known defender. Philosophers in his line, the Stanford entry reports, "find non-natural ethical qualities of any kind 'queer'," unlike anything the sciences discover. Mackie therefore denies the second premise. What makes him worth hearing is the concession he made on the first. As Wikipedia summarizes him, he accepted that "if objective moral truths existed, they would warrant a supernatural explanation." An atheist who denied objective morality agreed that, if it exists, the theist has the better account of it.

The second is evolutionary debunking. Sharon Street argues, in the Stanford entry's words, that "an evolutionary story about how we came to make the moral judgments we make undermines confidence" in their objective truth. Our ancestors who condemned betrayal and cared for their young left more descendants. If that history explains why we hold our moral beliefs, their truth plays no part in the explanation, and we lose our reason to think them true.

The third, and strongest, is secular moral realism. Erik Wielenberg defends what he calls "godless normative realism," and the Stanford entry grants that it "certainly provides a significant alternative to divine command metaethics." The realist accepts the second premise in full. Cruelty for its own sake really is wrong, whatever anyone thinks. What he denies is the first premise. Moral truths, on his view, are necessary and basic, like the truths of logic. Nobody asks what grounds the truth that two and two make four, and nobody needs to ask what grounds the wrongness of cruelty. It simply holds, in every possible world.

Behind all three stands Plato's old question in the Euthyphro, where Socrates asks "whether the pious or holy is beloved by the gods because it is holy, or holy because it is beloved of the gods." If God's command makes an act right, morality looks arbitrary. If God commands it because it is right, the standard seems to stand without Him. The Euthyphro dilemma has its own article. Here it serves the realist, who takes the second horn and adds that the standard needs no God at all.

Together the objections form a dilemma. Either moral facts are objective, in which case they may be brute necessities that need no ground, or they are not objective, in which case the second premise fails. On either side God seems idle.

Each volume of the series takes challenges like these at full strength.

Divine command, natural law and Kant: the standard answers

Christian philosophers have answered the challenge in three main ways. Each secures something the moral argument for God needs, and each strains at a point its critics have found.

Modified divine command theory is the answer most associated with the argument today. Robert Adams developed it, and Craig defends a version of it. Goodness is grounded in God's nature, and moral obligation is grounded in God's commands, which flow from that nature. To the Euthyphro, Craig replies that "the dilemma it presents is a false one" because "there's a third alternative: namely, God wills something because he is good." The Stanford entry agrees that "Adams' version of a DCT evades this dilemma by invoking the good/right distinction." The view explains why duty binds: it is the command of a Person with authority over us, not an impersonal fact.

It strains in two places. Critics say that if goodness is defined by God's nature, "God is good" becomes an empty tautology. And if obligation comes from commands, it is hard to say what binds those who have never heard them. A defender can reply that "God is good" is informative, because it names God as the measure against which finite goods are judged, and can meet the second charge with conscience, which carries a command to people who never read one.

Classical natural law is older. In the tradition of Thomism, the good of a thing is the perfection of its nature, and goodness and being are one. An eye is good when it sees well, and a human being is good when he lives as reason and love direct. Aquinas' fourth way reasons from the more and less good in things to a maximum that causes the goodness of all. Nothing here is arbitrary, since nothing is good by decree, and the good is not a rule above God, since God is the fullness of being from which every perfection comes. The strain is that the account rests on a metaphysics of being and perfection that much modern philosophy rejects, and critics charge it with moving from what a thing is to what it ought to do.

Kant's practical argument is the most modest of the three. It does not claim to prove God. It claims that a moral agent must will the highest good, which the Stanford entry describes as "a world in which people are both morally good and happy," and that only God can make such a world possible. Its strength is that it ties duty to hope: we act morally in the expectation that goodness will not finally be defeated. Its weakness is one Kant names himself. He wrote that "this moral necessity is subjective, that is, it is a want, and not objective." A need of reason is not yet a proof.

The secular realist has a strain of his own, and it is where the theist presses hardest. A brute moral fact explains neither its own authority nor our grasp of it. Why should a necessary truth about cruelty bind me, rather than merely describe something? And if moral facts cause nothing, how did minds shaped by survival come to track them? Street's debunking worry falls on the realist before it falls on the theist. A theist can say that the source of the moral order also made the minds that know it. The realist has no such answer to give.

Volume One introduces the method the next section applies, and you can read it free.

How Frame-Indexed Classical Theism answers the moral argument's critics

Frame-Indexed Classical Theism (FICT) is a research program in analytic theology that resolves classical theological dilemmas by diagnosing them as artifacts of a single error: one term carried across two frames as though it meant the same thing in each. Applied to morality, it agrees with divine command theory that God is the ground of moral truth, and with the secular realist that moral truth is necessary and objective. It locates the error in a debate both sides inherit, the quarrel between moral relativism and moral absolutism.

Volume Two, Resolving the Problem of Evil, takes that quarrel in its chapter on relativism and absolutism. As an account of what morality is, relativism is "an ultimately incoherent and self-refuting position." The debate endures because the two sides describe different things. "The moral relativist correctly identifies the epistemological predicament of fallen humanity," the book says, while "The moral absolutist correctly identifies the ontological truth of the universe." The relativist describes our access to the good: partial, pulled by culture and interest, uncertain. The absolutist describes the good itself. Read from our finite frame, morality looks situational. Read from God's, it is fixed. Each report is true of its own subject.

This is the distinction the moral argument needs. Its second premise does not require that our moral knowledge be stable or complete. It requires only that the standard be real.

What, then, is the standard? Volume Two answers that God "does not consult an external moral standard; He is the standard." The psalmists say it in worship:

"Righteousness and justice are the foundation of your throne; love and faithfulness go before you." (Psalm 89:14, NIV)

"You are good, and what you do is good; teach me your decrees." (Psalm 119:68, NIV)

God's goodness is not a quality He happens to have. By divine simplicity it is identical with His essence, which is why the tradition calls Him omnibenevolent. This dissolves the Euthyphro fork. The good is neither an arbitrary decree, since God's nature is not chosen, nor a law above God, since nothing stands above the one whose nature it is. Volume Five shows the same move at work on the truths of number.

It also meets the secular realist on his own ground. He is right that moral truth is necessary. He is wrong to leave the necessity floating. God exists from Himself by aseity, and a necessary moral truth that is the nature of the one necessary being needs no further ground and is no brute fact. God is the ground of being and the ground of the good at once. Because the same God made the minds that know the good, the realist's problem of access has an answer: our faculties track the good because they were made by it, though in a fallen world they track it imperfectly.

Paul says of Gentiles who never received the written law that they "show that the requirements of the law are written on their hearts, their consciences also bearing witness, and their thoughts now accusing, now even defending them" (Romans 2:15, NIV). Volume Two takes the verse at its word. Finite goodness, the honesty and courage of people who do not believe in God, is real and "commendable within our creaturely context." Craig says the same. His argument is "solely about the objective reality of moral values, not how we come to know them," and he adds, "I don't think that we need to appeal to God at all to know that objective moral values and duties exist."

But that knowledge is unstable. The serpent promised our first parents, "For God knows that when you eat of it your eyes will be opened, and you will be like God, knowing good and evil" (Genesis 3:5, NIV), an invitation to define the good from within. A finite creature, the book argues, "cannot generate an absolute moral framework from within." Cut off from its source, the mind has only circumstance, emotion and utility to measure by, and its certainty erodes. Reformed theology treats this reach of the Fall into the mind under total depravity. God answers it with revelation, which translates His nature into commands we can understand, and with regeneration, which gives a new nature that loves what it learns.

Where divine command theory leaves "God is good" looking empty and secular realism leaves moral facts brute, FICT defends the first premise by showing that only a being whose nature is the Good can ground an absolute standard while leaving our access to it real but partial. It removes the two objections that most often stall the argument, the Euthyphro fork and the claim that good atheists refute it. It does not claim that the argument, taken alone, compels belief. The statement of FICT sets out the whole position.

Volume Two takes relativism and absolutism in full; its book page lists every chapter.

Simulated attacks on the moral argument

Frame-Indexed Classical Theism has been tested against thousands of simulated attacks drawn from positions in the academic and peer-reviewed literature. Many press the same points critics press against divine command theory and secular moral realism, and two bear directly on the moral argument.

If our moral sense drifts toward relativism, how can we know objective morality?

Here's one of those attacks and how the Many Beings framework would address it.

The attack begins from a concession. Volume Two says the finite mind tends toward relativism without revelation and lacks the resources to keep a stable grasp of absolute truth on its own. Yet finite minds of every creed grasp the truths of arithmetic stably, and Volume Five calls those truths absolute. Which is it? Worse, if the fallen moral sense is unreliable, the theist seems to have sawn off the branch he sits on, because the second premise of the moral argument is known by that same moral sense. This is the debunking worry the Stanford entry attributes to Street, turned against the theist's own account.

The answer is that the attack reads a claim about moral knowledge as a claim about knowledge in general. Volume Two's chapter is about morality at every step: the creature "cannot generate an absolute moral framework from within," and the result it names is moral relativism. Nothing in it concerns arithmetic. On the point the attack treats as a contradiction, the two volumes agree. Volume Five says that "our access is relative; the reality accessed is absolute," and Volume Two says the same of the good: relativism is an accurate description of our uncertain moral experience, not of what is true. The argument needs only that the standard be real. Our moral knowledge can be partial and still be knowledge, because conscience bears witness even where it is unsteady.

Does "morality collapses without God" mean a creature can exist without God?

Here's one of those attacks and how the Many Beings framework would address it.

Classical theism, from Augustine and Aquinas onward, holds that no creature exists for an instant except as God holds it in being. Volume Six says the same: "no created cause operates for a single instant under its own power of being." Yet Volume Two calls moral relativism "the Epistemic Entropy of a closed system" and says the finite will tends toward the Fall "without sustaining grace." The attack asks whether that picture describes a creature cut off from God's sustaining, which classical theism says cannot exist. If so, the theist's diagnosis of secular ethics rests on an impossibility.

The sentence defines its own terms. The closure is epistemic, and the next clause says what it is: "the inevitable collapse of moral certainty that occurs when a finite being attempts to define the 'Good' apart from the Absolute." A closed system in this sense is a mind that refuses its source of moral knowledge, not a creature outside God's conservation. The grace in view is paired with "sustaining revelation," a gift that upholds the will and the mind in the good, and the volume distinguishes it from God's sustaining of the creature in being. That sustaining is never withdrawn; even the lost are "still held in existence by Him." So the secular moral realist is held in being at every moment, and knows a great deal. What he cannot do is generate the standard from within.

The series answers each attack on its own ground, and the books page shows where each lives.

Frequently asked questions

What are the premises of the moral argument?

In Craig's form there are two premises and a conclusion: if God does not exist, objective moral values and duties do not exist; objective moral values and duties do exist; therefore God exists. Sorley's older form runs the same way: if morality is objective and absolute, God must exist; morality is objective and absolute; so God exists. Both are valid. The debate is over the first premise, which the secular moral realist denies, and the second, which the error theorist denies.

Can you be good without God?

Yes, in the sense that people who do not believe in God know right from wrong and often do it well. Paul says the requirements of the law are written on the hearts of those who never received it (Romans 2:15). The moral argument does not deny this. Its claim concerns what makes moral truths true, not who can know them. It asks whether goodness could exist without God, which is a different question.

Does evolution explain morality?

Evolution may explain why we came to hold certain moral beliefs. It does not settle whether those beliefs are true, any more than the evolution of our eyes shows that what we see is unreal. The debunking argument presses hardest on the secular realist, whose moral facts cause nothing and so cannot have shaped the minds that know them. A theist can hold that the God whose nature is the standard also made the minds that track it.

Does the Euthyphro dilemma refute the moral argument for God?

No. The dilemma offers two options: the good is good because God commands it, or God commands it because it is good. Classical theism names a third. God commands what accords with His own nature, and that nature is the Good. It is neither chosen nor imposed from outside, so the good is neither arbitrary nor above God. The Euthyphro article takes the question in full.

Is the moral argument a proof of God's existence?

Its defenders usually present it as one strand of a cumulative case, alongside the argument from contingency and the others surveyed as evidence for God. Taken alone it argues that theism explains objective morality better than its rivals do. Its distinctive force is that it reaches not merely a first cause but a good one, a God whose nature is the standard of right.

Where the moral argument leads

Lewis's crooked line was a complaint against God that turned out to presuppose Him, and that is the moral argument's strength. A protest against injustice, even the protest of suffering that seems to tell against God, appeals to a straight line no human opinion drew. Relativism describes how dimly we see that line. It does not erase it, since we can call our sight dim only if there is something there to see. The line is drawn by the nature of God, the Good itself among the attributes of God, and the minds that see it dimly were made to see it clearly.

Volume One sets out the method from first premises, and it is free to download. The full series carries it from free will into evil, time and changelessness.