What's the Difference Between Agnosticism and Atheism?

Agnostics and atheists from the University of Wisconsin-Madison's Freethought Festival hold a rally for the separation of church and state outside the Wisconsin State Capitol. Box5/Getty Images

The "rise of the nones" it is called — the rapid increase in Americans with no religious beliefs that has taken place in the last decade or so. When Pew's Religious Landscape Study came out in 2015, it showed that the percentage of atheists in America had doubled from 1.6 in 2007 to 3.1 in 2014. Meanwhile, the percentage of agnostics had also doubled from 2.4 to 4.0. But what's the difference between agnostics and atheists? Is agnosticism just "atheism-lite"?

People choose to identify as religiously agnostic for a variety of personal reasons — philosophical, psychological, theological or even political. But it's wrong to think of all agnostics as "spiritual fence-sitters," unwilling to state whether they believe or don't believe in God. True agnosticism, it turns out, has nothing to do with belief at all.

Agnosticism Defined

The term "agnosticism" was first coined by English biologist Thomas Henry Huxley (1825-1895), a fierce defender of Charles Darwin against religious critics who accused him of denying God's role in creation. As a scientist, Huxley didn't bother himself with "beliefs." He sought after the truth. And the truth of any proposition — that God created the vast diversity of nature or that it evolved from natural selection — could only be proven by the evidence.

Huxley said that agnosticism itself wasn't a "creed" or set of beliefs, but a principle, namely "that it is wrong for a man to say he is certain of the objective truth of a proposition unless he can produce evidence which logically justifies that certainty."

The word itself was a combination of "a" (against or opposite) and "gnosticism," which comes from a Greek word meaning "knowledge." Gnosticism was a religious movement that flourished in the first and second centuries, that held, among other things, that the spirit world was good and the material world was evil. And although the principle of agnosticism doesn't exclusively apply to the question of God's existence — you can be agnostic about any proposition — it's been wrapped up in religion since the beginning. Huxley wrote a friend in 1860:

"I neither affirm nor deny the immortality of man. I see no reason for believing it, but, on the other hand, I have no means of disproving it... Give me such evidence as would justify me in believing in anything else, and I will believe that."

The Difference Between Agnosticism and Atheism

Atheism, according to its classical definition, is the lack of belief in God. (Whether that "God" is the biblical, Judeo-Christian God or some other "higher power" is a separate question.) The opposite of atheism is theism, the belief that God exists. Atheism and theism are "metaphysical claims," says Paul Draper, a professor at Purdue University who specializes in the philosophy of religion, because they deal with a fundamental question of the nature of reality.

Agnosticism, on the other hand, doesn't take a position on whether God exists. Instead, it takes a position on whether or not we can know if God exists. This, Draper explains, is an "epistemological" question, not a metaphysical one (epistemology is the study of knowledge). Agnosticism claims that we cannot know if God does or does not exist, because there's no compelling evidence that either proposition is true. At least not yet.

You might think that agnosticism is nothing more than a handy way to dodge the question of whether you believe in God. Instead of saying yes or no, the agnostic chooses a third position: neither.

But this is where things can get hairy, explains Draper, who wrote the Stanford Encyclopedia of Philosophy entry on Atheism and Agnosticism. "People get so angry about this," he says, referring to testy exchanges between atheists and agnostics online. "The atheists will say, 'You call yourself an agnostic but you're really an atheist!'"

And you can see the atheists' point. At face value, it seems like there's a razor thin line between saying "I don't see any evidence that God exists" and "I don't believe that God exists." But the truth is that you can be an agnostic and an atheist, just as you can be an agnostic and a believing Christian (or Buddhist or Muslim). That's because agnosticism, as its core, is separate and unrelated to questions of faith. Let's explain.

Agnostic Theism?

Agnostics are nearly always lumped together with atheists as a type of "non-believer." The Pew Research Center, defined religious "nones" as being either atheists, agnostics or not affiliated with any particular religion. But the fact is, you can be agnostic and also a true-believing, church-going religious dude.

"You could believe that God exists but not think you have enough evidence to make a knowledge claim," says Draper. In other words, you could believe on faith that God exists, but ascribe to the agnostic position that God's existence cannot be proven by physical evidence or rational arguments.

Such a person would be an agnostic theist. There's even a school of theology called apophatic theology that claims that God is inherently unknowable. Thomas Aquinas, the 13th-century philosopher and theologian, wrote, "Now we cannot know what God is, but only what God is not; we must therefore consider the ways in which God does not exist, rather than the ways in which God does."

While it's technically true that you can be both an agnostic and a faithful believer, it's far more common for agnostics to highly doubt the existence of God, even if they can't ultimately prove it. Bertrand Russell, the brilliant British philosopher and mathematician, wrote an excellent treatise on agnosticism in which he explained why the agnostic and atheist positions often overlap:

"The agnostic suspends judgment, saying that there are not sufficient grounds either for affirmation or for denial. At the same time, an agnostic may hold that the existence of God, though not impossible, is very improbable; he may even hold it so improbable that it is not worth considering in practice. In that case, he is not far removed from atheism. His attitude may be that which a careful philosopher would have towards the gods of ancient Greece. If I were asked to prove that Zeus and Poseidon and Hera and the rest of the Olympians do not exist, I should be at a loss to find conclusive arguments. An agnostic may think the Christian God as improbable as the Olympians; in that case, he is, for practical purposes, at one with the atheists."

As we said at the beginning, the reasons for identifying as agnostic are myriad and different for every person. Draper, who has participated in high-profile debates with Christian philosophers, calls himself a "local atheist" and "global agnostic."

"I'm an atheist about the all-powerful, all-knowing, all-good God," says Draper. "I'm agnostic about God in a broader sense. Is there some being that qualifies for the title God? There could be such a thing."

Learn more about agnosticism in "Agnosticism and Christianity and Other Essays" by Thomas Henry Huxley. You may also like "Why I am Not a Christian and Other Essays on Religion and Related Subjects" by Bertrand Russell. HowStuffWorks picks related titles based on books we think you'll like. Should you choose to buy one, we'll receive a portion of the sale.