Can the atheist prove that God does not exist?

One of my skeptical readers, EnoNomi, takes issue with my claim that atheists and agnostics shoulder an evidential burden to defend their belief just as much as the theist does. This is what EnoNomi writes:

"It's not up to the Atheist or the Agnostic to prove anything because you can't prove a negative. I can no more prove that your god doesn't exist than you can prove Odin or Zeus doesn't exist."

This is an important comment because it reflects a commonly held, but also incorrect view.

Let's begin with the notion of "proof". There are many kinds of proof. The highest standard is logical and mathematical proof in which the conclusion follows deductively, of necessity from the premises. Thus if the premises are certain, then that certainty carries forward to the conclusion as well. A very small amount of our knowledge reaches the standard of logical proof.

But there are many other kinds of proof as well, each appropriate to its type of knowledge. For instance, proof in a courtroom leaves open the possibility for logically possible alternative scenarios, but seeks to eliminate any relatistic alternatives. And within the courtroom there are different levels of proof. Criminal proceedings have a much higher standard -- beyond a reasonable doubt -- than do civil proceedings -- by a preponderance of the evidence. Most other types of proof (e.g. the proof offered by the historian or the economist) exist somewhere between these two standards of jurisprudence.

So now to God. What kind of standard of evidence is the atheist required to provide in order to justify disbelief in God? Logical certainty? Beyond a reasonable doubt? A preponderance of the evidence? Who decides?

It seems to me that there is no clear answer here. Rather, it seems most likely that the more evidence the atheist can provide, the stronger the justification for his/her belief. (Conversely, the more doubt the agnostic -- or weak atheist as some of my interlocutors prefer to say -- can cast, the stronger the justification for his/her withholding of belief.)

So back to EnoNomi's claim. Can I prove that Odin or Zeus do not exist? It all depends. I cannot provide a logical proof. But could I provide a lesser proof? Beyond a reasonable doubt? Or a preponderance of the evidence? I suspect I could. Certainly EnoNomi cannot simply declare by fiat that I cannot.

And this is what many atheists in fact attempt when it comes to the Judeo-Christian God: they seek to provide a lesser proof to support the conclusion that God does not exist. For instance, Vic Stenger attempts this in his book God: The Failed Hypothesis where he argues that current science warrants the conclusion that God does not exist. I may disagree, but Stenger is right that belief in God is up for critical review.

Atheist Austin Dacey has referred to this lesser proof approach as the "look and see" method. Essentially we engage in an a posteriori (or empircal) enquiry, looking to see whether the universe evinces signs of God's presence. If it does not then we can reasonably infer that God is absent or, to put it another way, that God does not exist.

But one can go further: it is also possible to develop a logical disproof for the existence of God. The way one would do so is by showing that there is a logical contradiction between certain attributes God possesses (e.g. a conflict between omnipotence and omnibenevolence) or between God's attributes and certain indisputable characteristics of the world (e.g. omnipotence, omniscience, omnibenevolence and the existence of evil).

As a committed Christian theist, I do not believe that the atheist has provided any of these proofs, though I do agree that there are certain lines of evidence which prima facie count against the existence of God as defined by the Christian theist.

But the main point here is that the atheist can in principle provide a weak or strong proof for God's non-existence. And thus the atheist cannot protest that such a thing cannot be expected of him or her because it is impossible.

There is a remaining grumble that one hears: as soon as a purported disproof for God's existence is provided, the definition of God is changed. Thus, theism is a target forever moving. For the moment I'll concede that this is occurring (that is, that the concept of God has evolved because of the proffering of disproofs for earlier concepts). But even if true, is that a ground for complaint? From the atheist's perspective it would just mean that he or she is guaranteed a job, forever knocking down new concepts of God like a centuries' old game of metaphysical Wac-a-mole.