The Two Greatest Logical Arguments for God’s Existence

Summary: William Lane Craig, a leading defender of belief in God, says the most persuasive arguments for God’s existence are the Cosmological Argument and the Moral Argument. What are they? I explain below.

There is perhaps no greater living defender of faith than William Lane Craig. A trained expert in both philosophy and debate, he’s amplified the logical arguments for God’s existence in the public sphere: debating leading atheists, speaking at hundreds of universities, influencing millions of students, authoring dozens of books, most recently On Guard: Defending Your Faith with Reason and Precision.

Craig sat down for an hour-long interview with Ben Shapiro, an Orthodox Jew and prominent young political conservative:

At 7:59, Shapiro asks Craig what he thinks is the most convincing proof of God’s existence. In it, Craig explains the Cosmological Argument:

Shapiro: What in your opinion is the most reasonable proof of God? What have you found to be the most convincing proof of God’s existence?

Craig: I think those are 2 questions. For me, my favorite argument for the existence of God, the one I find most compelling, is a version of the Cosmological Argument which goes like this:

  1. Whatever begins to exist has a cause. (Something can’t just come into being from nothing.)
  2. The universe began to exist. (We have both good philosophical and scientific evidence for the finitude of the past.)
  3. Therefore, the universe has a cause.

When you do a conceptual analysis of what it is to be a cause of the universe, you arrive at a being which is an uncaused, beginningless, timeless, spaceless, enormously powerful, personal creator of the universe.

For anyone who’s followed Craig over the years, this answer was no surprise: he’s the leading proponent of the Kalam Cosmological argument, as defined above.

I want to examine that argument a bit and the usual objections to it before we move on to the 2nd argument.

Cosmological Argument part 1:
Whatever begins to exist has a cause

This first assertion, called the Causal Principle, is empirically true: everything we see in nature has a cause to its existence. That tree exists because of a seed. The seed exists because the parent tree has DNA that instructs it to build seeds and release them. And so on. Ditto for inorganic matter like roads, rocks, stars, planets, and so.

The common atheist objection to this first step is, “Then what caused God?” If everything has a cause, then God has a cause; we haven’t solved anything. (There would have to be a thing or being which created God, and a being which created that being, and …)

Shapiro plays devil’s advocate and uses this exact objection at 10:11:

Shapiro: The [atheist biologist and author] Richard Dawkins comeback – the one you hear most frequently with regard to the finitude of time and the idea that everything has a cause – is, “Ok, well then, what caused God?”

Craig: It’s important to state the first premise correctly, Ben. It’s not “Everything has a cause.” It is, “Everything that begins to exist has a cause.” Something cannot come into being without a cause. But if something is eternal, never began to exist, there’s no need for a cause. So that objection to the argument is simply based on a misunderstanding of the first premise.

The problem with this objection is it’s a misstatement of the premise. The premise isn’t “Everything has a cause.” The premise is “Everything that begins to exist has a cause.”

This is an important nuance: everything that begins to exist has a cause. The corollary to this is the truism, “Things that are eternal do not have a beginning.” Thus, eternal things don’t necessarily have a cause.

And for the first half of the 20th century, scientists believed the universe itself was that eternal thing. That is, until scientific evidence arose during the 1960s showing that the universe definitely began to exist; it had a beginning. More on that in the next step.

A more sophisticated objection: “Why must we believe everything which begins to exist has a cause?”

One answer is, because that is what we observe in every circumstance and every measure of the natural world. We observe that there exists a cause for everything that comes into existence in the natural world. Science is the study and observation of the natural world; if we can’t theorize an idea which is observably true 100% of the time, then all our theories must be thrown out for lack of certainty.

Proponents of this objection rely on an earlier argument from 18th century philosopher David Hume that says “Effects without causes can be conceived in the human mind, and that which is conceivable in the mind is possible in the real world.

But proponents of this objection often overlook that Hume himself agreed with the Causal Principle, stating in a letter in 1754, “But allow me to tell you that I never asserted so absurd a Proposition as that anything might arise without a cause.

From everything we observe in the natural world, everything that has a beginning has a cause for its beginning.

Cosmological Argument part 2:
The universe began to exist

The atheist physicist Stephen Hawking called this the most remarkable discovery of 20th century cosmology:

All the evidence seems to indicate that the universe has not existed forever, but that it had a beginning, about 15 billion years ago. This is probably the most remarkable discovery of modern cosmology. Yet it is now taken for granted.

-Stephen Hawking, physicist

For the early part of the 1900s, scientists believed the universe must be eternal. If it’s eternal, it had no beginning. And if it had no beginning, it had no cause for its existence. Problem solved!

But not all scientists were convinced. In the early 20th century, scientists theorized that if the universe did have a beginning, we’d see some evidence for that in the form cosmic microwave background radiation; an audible echo of the instant of creation.

And in 1964, American astronomers Robert Wilson and Arno Penzias discovered a faint background noise in the space between stars and galaxies. This was later confirmed as electromagnetic relic radiation, a corroboration of the instant the universe began. This discovery, for which Wilson and Penzias received Nobel prizes, overturned science’s understanding of the universe’s finitude.

Today, modern science affirms the universe had a beginning; this is well-accepted and not at all controversial.

Philosophically, it’s also on solid ground. Craig elaborates the problems with an eternal universe at 10:56:

Shapiro: Must we posit an eternal being? Or could we just have an infinity of regressive causes?

Craig: That’s the 2nd premise: the universe began to exist. There are deep philosophical problems with the idea of an infinite past. For example, how did we get to today if you had to go through an infinite number of prior events one at a time? That would be like trying to count down all the negative numbers one at a time ending at zero; an absurd task.

Moreover, we have remarkable scientific evidence from the Big Bang expansion of the universe, and the thermodynamic properties of the universe, which suggest the universe cannot be infinite in the past, but must have had a beginning around 13.8 billion years ago.

So I think that 2nd premise is very powerfully supported both philosophically and scientifically.

Cosmological Argument part 3:
Therefore, the universe has a cause

Step 1 was an assertion based on observable reality: anything that has a beginning has a cause. Step 2 was a statement of scientific fact: the universe has a beginning. Step 3, the final step, arrives at a conclusion based on the previous 2 steps: since the universe had a beginning, and since everything that begins to exist has a cause, then the universe has a cause.

Since the universe can’t cause itself, the thing that caused it must be outside of the universe: immaterial.

Time, we believe, is a property of the universe. So the thing that caused the universe must be outside of time; timeless and eternal.

Timeless and eternal things don’t necessarily have a cause (see step 1). Thus, the thing that caused the universe must be uncaused.

Finally, whatever caused the universe to come into existence had to produce all the energy we now witness in the universe, for all of history. From the excitement of molecular particles to the eventual planets spinning in motion and stars bursting into flames: the thing that caused the universe must be extraordinarily powerful.

Cosmologists and philosophers are left with a remarkable question: what immaterial, timeless, eternal, uncaused, and extraordinarily powerful thing could create the universe?

The Moral Argument

Craig says the Cosmological Argument is his favorite and most compelling to him personally. But he says the argument that is most persuasive to students he speaks with is the Moral Argument for God’s existence. Craig explains at 9:00:

Craig: I find that with university students [the Cosmological Argument] is not the most convincing argument. You can ignore philosophical arguments for the finitude of the past, or even scientific evidence for the beginning of the universe. But the argument they find the most compelling is what I call the Moral Argument. It goes like this:

  1. If God does not exist, then objective moral values and duties do not exist. (That is to say, in the absence of God, everything becomes socio-culturally relative.
  2. Objective moral values and duties do exist. (There are some moral absolutes, some objective values and duties.)
  3. Therefore, God exists.

This is an argument which is impossible to ignore because everyday you get up, you answer by how you treat other people, whether you regard them as having intrinsic moral value, or whether they’re mere means to be used for your ends.

The Moral Argument says that if God doesn’t exist, we should not see any absolute or objective moral values; it’s purely relative. What’s bad for you may be good for another: relative morality.

But, because we do see objective, absolute moral values in the world, objective morality exists, and if objective morality exists, then God exists.

Craig says this argument tends to hold more weight with most people, especially university students, because doing good (moral absolute good) is something every person grapples with each day.

One common objection to this argument is the idea that primitive moral values (e.g. protection of kin) are seen in other mammals, and therefore must be programmed in biologically; no God needed.

At 11:53, Shapiro raises this objection:

Shapiro: The other argument, the Moral Argument, in contravention of that: [there is] an argument made by [leading atheists] Dawkins, Harris, and evolutionary biologist Brett Weinstein that there is a certain sense of morality that is innate to mammals that you see even in species that are not our own. A sense of primitive altruism, a sense of kinship protection, for example. So is it possible that morality is embedded on a very basic level in behavior of mammals beyond the idea of an objection morality that we think about and enact? That it’s just embedded in the natural code?

Craig: This response [to the Moral Argument] is almost a textbook example of the genetic fallacy. The genetic fallacy is trying to invalidate a point of view by showing how that point of view came to be held. Even if evolution and social conditioning has programmed into us a certain set of moral beliefs, that does nothing to show that those beliefs are false. Indeed if moral values are gradually discovered rather than gradually invented, then our gradual and fallible apprehension of the moral realm no more undermines the objectivity of that realm than our gradual, fallible comprehension of the physical world undermines the objectivity of the physical realm.

In the absence of some defeater, it seems to me that we’re perfectly within our rights in believing that there is an objective realm of moral values and duties, just as we’re within our rights in believing there is a world of physical objects around us.

It’s worth clarifying: by “objective” morality, we mean something that is true, regardless of circumstance or the person uttering it. For example, “rape is immoral” is a statement of absolute morality; there’s not a case where rape is could be moral for you, but immoral for another. It’s always absolutely wrong (a sin) to do so.

Craig’s response in a nutshell is that when atheists claim there is no objective morality because we see primitive morality programmed into intelligent mammals, it does nothing to invalidate the claim of objective morality. Craig is saying that even if objective morality is gradually discovered by humans, or even shared on some level with mammals, objective morality still exists.

Humanity’s gradual discovery – rather than invention – of objective morality doesn’t invalidate objective morality. (By the same measure, says Craig, our gradual discovery of objective morality is just as valid as our gradual discovery of the natural world.) Even if some morality is pre-programmed biologically, that doesn’t invalidate the reality of objective morality.

(An anecdotal aside: preaching from Romans at my local Messianic congregation this year, I argued precisely this: that there is programmed into every human being basic morality. I believe the Apostle Paul makes that case in Romans 1. That basic or primitive morality comes biologically packaged doesn’t invalidate the existence of objective morality.)


Craig argues these two are the most persuasive logical arguments for God’s existence:

The Cosmological Argument

The Moral Argument

1. Whatever begins to exist has a cause. 1. If God does not exist, objective moral values do not exist.
2. The universe began to exist. 2. Objective moral values do exist.
3. Therefore, the universe has a cause. 3. Therefore, God exists.

I personally find the Cosmological Argument most convincing, because step 1 is empirically true, step 2 is scientifically true, and step 3 is a logical conclusion from those assertions.

(Meanwhile, I find the moral argument more based in emotion and perception, even though it is likely true that without a moral root – God – then morality cannot be objective or absolute.)

Are these compelling arguments to you, fine reader?