What Does It Mean to Believe (or Not Believe) in God?

Imagine a friend tells you there’s a giant invisible rabbit living in their basement. You’ve never seen it, heard it, or found any footprints. You can’t prove it isn’t there—maybe you could, if you searched the whole basement carefully, but you haven’t. So what’s your position? You probably don’t believe the rabbit exists. But does that mean you believe the rabbit doesn’t exist? Those feel like different things, right?

This is the kind of puzzle philosophers have been tangled up in for a long time—except instead of rabbits, they’re thinking about God. The questions sound simple: What is an atheist? What is an agnostic? Are they the same thing? Different? Can you be both? But as soon as you start looking closely, things get surprisingly complicated.

What “Atheism” Actually Means

Here’s a strange thing: philosophers don’t all agree on what “atheism” means. In fact, they disagree pretty sharply.

In everyday conversation, people often use “atheist” to mean “someone who doesn’t believe in God.” That seems straightforward enough. But philosophers have noticed something: there’s a big difference between not believing something and believing the opposite. Not believing there’s a rabbit in your basement is one thing. Believing there definitely isn’t one is another.

Most philosophers prefer the second, stronger meaning. For them, an atheist is someone who denies that God exists—someone who says “God does not exist” is a true statement. This isn’t just being picky about words. When you’re trying to figure out what’s true, it matters whether you’re taking a definite position or just sitting on the fence.

Think about it this way. If someone asks “Does God exist?” there are only two direct answers: “yes” (which is theism) and “no” (which is atheism). “I don’t know” or “Nobody can know” are perfectly reasonable things to say, but they’re not direct answers to the question itself. Philosophers find it useful to have a word for that “no” answer.

But not everyone agrees. Some philosophers—and many non-philosophers—prefer the broader definition. They want “atheist” to include anyone who simply lacks belief in God, even babies, or people who have never thought about it. This makes political sense, since there’s strength in numbers when people who don’t believe face bigotry. But it creates odd situations. For example, someone could be a devoted member of a church, just not very confident about God’s existence, and technically count as an atheist on this definition. That seems weird.

What About Agnosticism?

The word “agnostic” was invented in the 1800s by a biologist named T.H. Huxley. He was tired of people being absolutely certain about things nobody really knew. His basic idea was: if you don’t have good evidence, you shouldn’t claim to know. And since he didn’t think there was good evidence either for or against God’s existence, he said we should suspend judgment.

This is how most people use “agnostic” today: someone who isn’t sure, who hasn’t made up their mind. But again, philosophers have noticed a wrinkle.

Remember the difference between not believing something and believing the opposite? A similar distinction applies here. There’s a difference between:

Psychological agnosticism: the state of not believing either way (neither believing God exists nor believing God doesn’t exist)
Epistemological agnosticism: the view that nobody knows whether God exists (or that neither belief is justified)

These are different! You could be an epistemological agnostic—thinking nobody really knows—while still being a theist or atheist yourself. Some religious people, called fideists, say that reason can’t tell us whether God exists, but they believe anyway through faith. They’re agnostic in the epistemological sense but not in the psychological sense.

And you could flip it the other way too. Some atheists call themselves “agnostic atheists”—they believe God doesn’t exist, but they admit they don’t know this for certain.

The Question of Which God

Here’s another twist. When someone says “I believe in God” or “I don’t believe in God,” which God are they talking about?

The God of classical Western religion—all-powerful, all-knowing, perfectly good, the creator of everything—is just one concept among many. There are also panentheistic Gods (where the universe is part of God but God is more than the universe), process theistic Gods (where God changes and grows), deistic Gods (who created the universe but doesn’t interfere), and Gods from non-Western traditions with very different characteristics.

Most atheists are actually “local atheists”—they deny the existence of one particular kind of God (usually the classical one). “Global atheism”—the claim that no God of any kind exists—is a much harder position to defend. You’d have to examine every legitimate concept of God ever conceived and show that none of them is instantiated. Very few atheists have done anything close to that.

A philosopher named Jeanine Diller pointed this out. She argues that most atheists don’t even realize how many different concepts of God there are. The strongest arguments for atheism usually target just one specific version—usually the all-powerful, all-knowing, perfectly good creator. Those arguments, even if successful, don’t touch the other versions.

Two Arguments That God (Probably) Doesn’t Exist

Despite these complications, philosophers have developed some sophisticated arguments for at least local atheism. Here are two interesting ones.

The Low Priors Argument

Imagine you’re at the starting line of a race. Some hypotheses start the race already far behind because they’re very specific—they claim a lot of detailed things that could be wrong. Other hypotheses are more general and take fewer risks.

The basic idea of this argument is that omni-theism (belief in an all-powerful, all-knowing, perfectly good creator) is an extremely specific hypothesis. It claims not just that some mind created the universe, but that this mind has exactly these particular features: omnipotence, omniscience, moral perfection, eternity, non-physicality. Each of these added details makes the hypothesis riskier—there are more ways it could be wrong.

Compare it to “source physicalism”—the view that physical stuff existed before mental stuff and caused minds to come into existence. This is a much simpler, less specific claim. (It doesn’t require minds to be nothing but physical stuff, just that minds depend on physical things.)

The argument goes like this:

The evidence we have doesn’t favor omni-theism over source physicalism.
Source physicalism is many times more probable before looking at any evidence simply because it’s less specific.
Therefore, source physicalism is many times more probable overall.
Therefore, omni-theism is very probably false.

Of course, premise 1 is controversial. Theists think the evidence—the complexity of the universe, the existence of consciousness, the fine-tuning of physical constants—does favor their view. But defenders of the argument respond that when you look at the full evidence, including all the specific details about how consciousness depends on brains and how suffering works, the advantage disappears. The Lord giveth and the Lord taketh away.

The Decisive Evidence Argument

This second argument takes a different approach. Instead of comparing omni-theism to a completely different hypothesis, it compares it to something very similar—“aesthetic deism.”

Imagine a God who is all-powerful and all-knowing, just like the omni-God, but with one crucial difference: instead of being motivated by moral perfection, this God is motivated by aesthetic concerns. This God wants to create a beautiful story, a grand narrative with drama and struggle and meaning.

Now, if you were writing a story, would you make everything work out perfectly for everyone? Probably not. Good stories need conflict, danger, loss, and suffering. The best stories have a mix of good and evil, happiness and tragedy.

This is where the argument gets interesting. The world we actually see—with its strange mixture of pleasure and pain, love and cruelty, flourishing and suffering—fits perfectly with what you’d expect from an aesthetic God. But it’s harder to explain why a morally perfect God would allow so much horrible suffering, especially when preventing it wouldn’t ruin any meaningful story.

The Book of Job in the Bible might actually support this. Job, a good man who suffers terribly, demands an explanation from God. God’s response? A speech about the grandeur of creation—the stars, the animals, the seas. God never actually answers the moral question. It’s as if God is saying: “Look at the beauty and power of what I’ve made. That’s what matters.”

If this argument works, it doesn’t prove there’s no God. But it does suggest that if there is a God, that God probably isn’t the morally perfect being of traditional religion. And that makes omni-theism very probably false.

The Problem of Uncertainty

Nobody really knows whether God exists. That’s the honest truth. Philosophers still argue about all of this, and they will probably keep arguing for a long time.

Some arguments for atheism try to show that God’s existence is very improbable. But even if they succeed, there’s a further question: does that make it rational to be an atheist? Or should you suspend judgment?

This gets into tricky territory about what it means to believe something rationally. Imagine a lottery with a million tickets. You know for certain that exactly one ticket will win. For each individual ticket, you can be extremely confident it will lose—99.9999% confident. Is it rational to believe that a particular ticket will lose? Most people would say yes. But here’s the problem: if you believe that each ticket will lose, you’re committed to believing that no ticket will win—which you know for certain is false. So you can’t rationally believe all those things together, even though each individual belief seems rational.

This is called the “lottery paradox,” and it shows that what counts as rational belief isn’t as simple as “whatever is very probably true.” Some philosophers think this means you’re never rationally required to believe or disbelieve in God—you should just suspend judgment. Others think you can rationally believe God doesn’t exist, as long as you don’t claim to know it.

The debate continues. And that’s okay. Some of the most interesting questions don’t have clean answers.

Key Terms

Term	What it means in this debate
Theism	The claim that God exists
Atheism	The claim that God does not exist (in the standard philosophical sense)
Agnosticism	Either the state of not believing either way, or the view that nobody knows whether God exists
Omni-theism	Belief in a God who is all-powerful, all-knowing, and perfectly good
Local atheism	Denying the existence of one particular kind of God
Global atheism	Denying the existence of any kind of God at all
Intrinsic probability	How probable a claim is before looking at any evidence, based only on its content
Source physicalism	The view that physical things existed before minds and caused minds to exist
Aesthetic deism	The view that a powerful, knowing God created the universe but is motivated by beauty and story rather than morality

Key People

T.H. Huxley – The biologist who invented the word “agnostic” in the 1800s because he thought people shouldn’t claim to know things without evidence
Jeanine Diller – A philosopher who pointed out that most atheists only deny one kind of God and haven’t considered all the others
Robin Le Poidevin – A philosopher who argued that agnosticism is the most reasonable position because we have no firm basis to judge whether theism or atheism is more probable

Things to Think About

If someone says “I don’t believe in God” but also says “I don’t believe God doesn’t exist,” are they an atheist? An agnostic? Neither? Does it matter what label they choose for themselves?
The “God of the gaps” idea says that as science explains more things, God gets pushed into smaller and smaller spaces. But if science can’t disprove God, is that a problem for atheism? Can something be rationally believed even if it can’t be proved?
Suppose you became convinced that a morally perfect God couldn’t exist because of all the suffering in the world. Would that make you an atheist? Or would you just switch to believing in a different kind of God—one who isn’t morally perfect? What’s the difference between these two moves?
If a belief is very probably true but you can’t be certain, is it rational to believe it? What about the lottery example—does that change your thinking about what counts as rational belief?

Where This Shows Up

Law and politics: Courts sometimes have to decide what counts as a “religion” or whether atheism deserves the same protection as religious beliefs. The definition matters for real legal cases.
Everyday arguments: When people debate whether God exists online or in person, they’re often talking past each other because they’re using different definitions of “atheist” and “agnostic.”
Science vs. religion debates: Many arguments between scientists and religious believers assume a particular definition of God (usually the all-powerful, all-knowing, perfectly good one) without considering other possibilities.
Your own thinking: The next time you hear someone say “I’m agnostic,” you might wonder: do they mean they haven’t decided, or do they mean they think nobody can know? Those are two very different positions wearing the same hat.