internet. They are usually entertaining and informative dialogues between philosophers, scientists, theologians, and authors who are trying to sell their books about the existence or non-existence of God. One of the important points in these debates is to establish who has the burden of proof. Usually, it's the person making a claim who needs to present evidence for their claim. This is paramount.
So who is actually making a claim during a debate about the God's existence? The believer usually tries to say that it's the atheist who is making the claim that there is no God. When the atheist fails to prove God's nonexistence, the believer then claims victory - as if God exists by default if His existence can't be disproved.
However, there is something illogical about placing the burden of proof on the atheist. To understand why, ask yourself if you could disprove the existence of an invisible unicorn? Could you prove that fairies do not exist? Could you prove that Zeus or Jupiter do not exist? Despite the fact that you don't believe in these mythical creatures and once-revered gods, you also can not disprove their existence. Nobody can. Why? Because you can't disprove something doesn't exist. You can't disprove a negative. Whatever it is (a God or ghost), it could always exist in some undiscovered part of the universe - or better yet, it could exist "outside of nature" all together - safe from any possible examination. Or maybe we just don't have the right tools to locate God with (such as the skeptics lack of faith). Maybe God doesn't want to be found, and therefore makes it impossible to do so. But this doesn't mean He doesn't exist. Although this is not very convincing, God (or Zeus) could theoretically still be out there. Therefore, you can't disprove the non-existence of something; even something as improbable as invisible unicorns, fairies, or the parody God who goes by the name The Flying Spaghetti Monster.
Bertrand Russell, the great 20th century philosopher, used a famous analogy (sometimes called Russell's teapot) which is pertinent to the issue of who has the burden of proof for the existence of God:
If I were to suggest that between the Earth and Mars there is a china teapot revolving about the sun in an elliptical orbit, nobody would be able to disprove my assertion provided I were careful to add that the teapot is too small to be revealed even by our most powerful telescopes. But if I were to go on to say that, since my assertion cannot be disproved, it is an intolerable presumption on the part of human reason to doubt it, I should rightly be thought to be talking nonsense. If, however, the existence of such a teapot were affirmed in ancient books, taught as the sacred truth every Sunday, and instilled into the minds of children at school, hesitation to believe in its existence would become a mark of eccentricity and entitle the doubter to the attentions of the psychiatrist in an enlightened age or of the Inquisitor in an earlier time.Just as one cannot disprove something as improbable as an orbiting teapot between Earth and Mars, similarly, one cannot disprove the existence of God. Even though there is not the slightest evidence for the existence of such an invisible celestial teapot, you could not disprove it. But belief in God (or orbiting teapots) would make sense if, as Russell points out, it were drilled into your heads from the time you were small children by parents, society, and preachers, reinforced at weekly worship services, and affirmed in holy scripture.
It should now be obvious that it is an impossible task (and a sneaky debate tactic) to try to get an atheist to disprove the existence of God. The burden of proof does not lie with him; it lies with the theist who is making a claim of knowledge! This is an important principle that operates in any respectable court of law. For example, could you imagine a court of law where the burden of proof lies with the defendant to prove his innocence, rather than with the prosecutor to show beyond reasonable doubt that the accused is guilty? Clearly this would be absurd (and reminiscent of the Salem witch trials or the Inquisition).
Next, just because one cannot disprove god's existence, it does not logically follow that the default position is therefore belief in God, or that there is somehow a 50:50 probability for God's existence. Similarly, just because you can't disprove the existence of orbiting teapots doesn't mean that they exist by default, or that the probability of them existing is somehow 50:50. And yet this is what many theists seem to say when they claim that their belief is somehow equiprobable since it cannot be proved to be false.
It must finally be said that atheists are not even making a claim of knowledge to begin with! Atheists (well, at least weak atheists like me) are just saying that we don't BELIEVE in God. Atheism literally means "without belief in God or gods." We're not claiming to KNOW God doesn't exist. We just don't believe in God or gods. That's it! Nothing more. Atheists will argue that there aren't good reasons to believe in God. However, this is not making a claim of knowledge; it's just refuting the evidence that believers give. It's really the opposite of a knowledge claim. Very few atheists go any further, as some positive or strong atheists do, to claim that God does not exist. This claim, as we saw with Russell's teapot analogy, is not tenable. But neither is the existence of God (like Russell's teapot) probable just because it can't be disproved.
So why don't those damned atheists believe like everyone else? There is a long answer to that question. But the best short answer was given by Stephen Roberts, who said "When you understand why you disbelieve in all the other possible gods, you will understand why I dismiss yours." Early Christians were even called atheists because they rejected the contemporary pantheon of gods that most people worshiped. In a similar vein as Roberts, the Oxford biologist Richard Dawkins said "We are all atheists about most of the gods that societies have ever believed in. Some of us just go one god further."
In sum, atheists don't believe in God or gods because there is a significant lack of evidence - or at least evidence that is convincing. When Bertrand Russell was asked what he would say to God, if he were hypothetically to meet him at the pearly gates, his response was "Not enough evidence God, not enough evidence." The burden of proof, or requirement of evidence, lies with the person making a claim of knowledge. And in the case of religion, the claimant of knowledge is the theist. What that evidence is, (and it's validity) is a topic for another post.