The burdens of proof
As long as I can remember, people have presented me with arguments that allegedly prove the existence of God. Some of these arguments were presented by Catholic priests, others by members of other faith communities, but always, they strove to employ logic in ways that were supposed to persuade me that the existence of God was irrefutable. As a child, I generally accepted these arguments…after all, at that point in my life I had no basis to question them. But eventually I began to question the validity of these proofs. Even when the arguments conveyed a logical consistency, I often found that the starting point of the argument didn't ring true to me. And over time, I came to see that most of these arguments were really just philosophical constructs, and not anything that could be considered actual proof. My education in engineering showed me the value of the scientific method, and taught me how to evaluate evidence and showed me that absolute proof is very rare indeed.
I have gradually come to understand that the very concept of God defies proof. The God of Christianity is, by definition, beyond our ability to comprehend. And if we are incapable of understanding such an entity, then we have no hope of finding evidence that proves that it exists. Many believers understand this…for them this is the whole point of faith. Believing in God is a choice, a blind leap into accepting the unknowable. And I don't really have a problem with that, as long as people understand that there really isn't any real evidence to support that belief. For myself, I have come to understand that not only is there no evidence that God exists, but also that such proof is essentially impossible.
Believers often challenge atheist to prove that God doesn't exist. But just as it is impossible to find evidence to prove the existence of God, it is equally impossible prove that there isn't any God. Again, the very nature of the God that most people believe in precludes any possibility of proof, whether positive or negative. According to most believers, God exists outside the laws of science and nature, which means that there can be no measurable evidence that can be analyzed in order to assess the merits of any claims for or against the existence of such a supernatural being. Simply put, it is fundamentally impossible to prove either that God exists or that he doesn’t.
Since skeptics are just as incapable of disproving the existence of God as believers are of proving it, the atheist view is also one of belief. Just as the faithful choose to believe that God exists, the atheist chooses to believe that there is no God. Superficially, this suggests that atheism is a choice that is on par with the faith chosen by believers. But that that apparent equivalence fails to take into consideration the difference in the burden of proof for the two sides.
It is a principle of evidentiary analysis that extraordinary claims require corresponding extraordinary evidence to support them. When simpler explanations fit all of the available evidence, then these should be preferred to more complicated or extraordinary solutions. This idea, that the simplest answer that fits the available evidence is the correct one, is sometimes called “Occam’s Razor”, and it governs the rational choice between competing theories. When considering the existence of God, the claim that a God that exists outside our understanding of the natural world is the more extraordinary claim (relative to the claim that God does not exist at all), so that there is a higher burden of proof required to sustain that position. In contrast, the position that God does not exist at all is actually less exceptional, since the existence of God is not required to explain any other theories supported by the evidence. Thus the burden of proof is lower, and in the absence of evidence to the contrary, the default conclusion should be that God does not exist.
Of course, all of this is predicated on the utter lack of evidence regarding the existence of God. Should such evidence ever present itself, then we would need to revisit this question and reevaluate our conclusions in light of that evidence. In the meantime, it is entirely rational for skeptics to conclude that the evidence (or. more precisely, the lack thereof) points to the conclusion that there is no God.