Some people choose to say, "I'm not an atheist; I'm an agnostic," as a way of softening the blow when explaining their lack of belief. Others might view agnostics as fence-sitters or people who simply can't make up their minds. However, agnosticism is not an independent viewpoint that exists outside or between atheism and theism, and it's not mutually exclusive with atheism. Agnosticism answers an entirely different question than atheism. Atheism is an answer to "Do you believe any gods exist?" On the other hand, agnosticism is answer to "Do you know whether any gods exist?" Therefore, it's quite possible to be both an atheist and an agnostic: you do not claim that there is absolute evidence to definitively disprove every definition of God, but you also do not believe that any deities exist.

Explaining Agnosticism

The word "agnostic" comes from Greek roots meaning "without knowledge." One could be agnostic about many things, but it's most commonly used in the context of religious belief. When it comes to belief in a deity, there are two basic stances to take: either you can believe that God exists, or you can disbelieve. When you further examine those options, though, there are four stances to choose from, depending upon knowledge:

1. Gnostic Theist: You believe in God and "know" this to be true.
2. Agnostic Theist: You believe in God without “knowing” whether it's true.
3. Gnostic Atheist: You disbelieve in God and "know" this is true.
4. Agnostic Atheist: You disbelieve in God without “knowing” whether it's true.

The third claim is considered "gnostic atheism" and could otherwise be described as, "I believe and ‘know’ that God does not exist." The fourth claim, meanwhile, is agnostic atheism: "I do not believe that God exists, but I don’t ‘know’ God’s non-existence to be true." The difference between these claims is subtle but important to understand.

The Burden of Proof

Imagine that I approach you with an unlikely claim: I have a two-foot-tall leprechaun living in my closet. I'm the only person who can see this leprechaun, and he leaves no physical evidence of his existence. There is no way for anyone to say definitively that he does not exist, but I also cannot offer a shred of evidence that he does. This is the very definition of an unfalsifiable claim.

When it comes to a claim that is unfalsifiable, the burden of proof is always on the person making the assertion. To do otherwise would be to invite absurdity. Take, for example, any of the many thought experiments regarding unfalsifiable claims, such as the Flying Spaghetti Monster, the Invisible Pink Unicorn or Sagan's "The Dragon in My Garage" and Russell's Teapot. In each case, as in the leprechaun example above, the thought experiment involves a story about a fantastic and impossible creature whose existence cannot be entirely refuted but also cannot be proven.

This is where agnosticism becomes a valuable stance to take in regards to theistic belief. Agnostic atheists admit that they cannot definitively prove that there is no God. They can, however, point out the utter lack of proof that one does exist and choose not to believe.

Some Claims Can Be Refuted

The above line of reasoning applies only to unfalsifiable claims, or claims that cannot be proven to be true or false. While this description applies to many religious beliefs, other religious claims can, in fact, be refuted with relative certainty. This is because the claims themselves are internally inconsistent and break down in the face of logic.

Take, for example, the Abrahamic God worshiped variously by Jews, Christians and Muslims. Supposedly, the Abrahamic God is simultaneously all-knowing, all-powerful and benevolent. These three traits cannot coexist with the world that we can perceive. When a major catastrophe occurs and wipes out thousands of people, it's impossible to assert that a benevolent and all-powerful God could be responsible.

Either God is impotent with no power to stop such a disaster, or he simply does not care about the suffering of humans. So while it may not be possible to disprove the existence of every definition of God, it is certainly possible to refute gods defined with contradicting attributes.

The Spectrum of Theistic Probability

As with many facets of life, theism and atheism lie on a spectrum rather than a strict binary. Richard Dawkins popularized the idea of a spectrum of theistic probability in his book, The God Delusion. In it, there are actually seven positions to hold:

1. Strong theism, which asserts that the believer knows without a doubt there is a God.
2. De facto theism, where believers are not 100 percent sure that God exists but consider it very probable and live their lives as though he does.
3. Weak theism, where a believer isn't wholly certain but leans toward belief in a deity.
4. Pure agnostic or complete impartiality, where the likelihood of a god's existence is just as likely to be true or false.
5. Weak atheism, where an individual isn't certain whether God exists but is inclined toward skepticism.
6. De facto atheism, where a person is not wholly positive that God does not exist but considers it very improbable and lives his/her life as though there is no deity.
7. Strong atheists, who believe with 100 percent certainty that there is no deity.

According to Dawkins, position six is more common than seven among atheists. If you were to rate your beliefs on the Dawkins scale, where would you classify yourself?