I’m sure we’ve all heard theists say “you can’t prove God doesn’t exist, therefore I’m justified in believing he does!” Yes, we get into concepts like burden of proof, which rarely ever goes over well, but there’s another tool in our belt that we far too often forget about and that is falsifiability.
Falsifiability is essential in basic logic, it is the concept that the proper position to hold is the one which requires the least amount to prove wrong. In very general terms, this means that we ought not believe things are real unless they are supported by objective evidence because the opposite is difficult, if not impossible to falsify.
For gods, this concept is easy. If we take the position that gods exist, in order to falsify the claim, we’d have to examine the entire universe, and with some concepts of gods, outside of the universe, and find no evidence for the gods. That’s a clearly impossible proposition. However, the reverse position, that gods do not exist, is extremely easy to falsify, simply produce a single example of a god.
Of course, this isn’t going to go over well with the theists either, nothing ever does, but it’s not something they can easily turn around. This goes back to Karl Popper’s “problem of demarcation”, where he tries to determine the difference between scientific claims and unscientific claims and comes up with falsifiability as the line of demarcation between the two. We also find that Wolfgang Pauli, famous theoretical physicist and one of the pioneers of quantum mechanics, who said of arguments which cannot conceivably be demonstrated wrong via experiment, “it is not only not right, it is not even wrong!”
Popper got his start in the 1930s with arguments like:
I observe a white swan, therefore… all swans are white.
It may very well be difficult to observe all swans in the world but it certainly is possible to produce an example of a non-white swan, should you find one, thus falsifying the statement. This is called an inductive categorical inference. It is what we most commonly encounter and therefore people need to be most aware of it. Keep in mind that just because someone can inductively reason the above, it isn’t necessarily correct, just because we haven’t found any black swans, it is merely falsifiable because there is the possibility that we can find a black swan and prove it wrong.
This becomes more difficult when someone argues that there is a unicorn somewhere in the universe. This is not reasonably falsifiable, we cannot check out every planet, every asteroid, every single location in the universe, at the same time, to prove that there are no unicorns in any of them. What if the unicorns are magical and can travel at the speed of light and don’t need an atmosphere to survive. No matter where we looked and didn’t find them, the believer can say they simply moved on before we arrived. That’s essentially what the religious say with regard to their gods. Their deities are non-falsifiable because they are constructed in such a manner that we can never, by definition, find them. I’ve pointed out in the past that how people saw their gods has evolved over time. Back in the days of the ancient Hebrews, for instance, the gods directly interacted with mankind. There are stories in the Bible of God speaking to, walking with and causing miracles for humanity. This is also true in other mythologies, such as the Greeks. Yet as man advanced, as man found ways to climb Mount Olympus, the religious had to keep moving their gods around to make them impossible to falsify. When you got to the peak of the mountain and found no gods, the religious had to explain why they weren’t there. They were invisible. They were hiding. It doesn’t matter what excuse they invented, it was to place them beyond the bounds of human examination. As we got better at looking at the world around us, the gods got better at hiding, or at least their followers got better at inventing new hiding places. Eventually, theists gave up the pretense of direct human/deity interactions and just declared them to be completely beyond any reasonable evaluation of their existence. However, these claims are not falsifiable, any more than my magical space unicorn example, and therefore, rational people must reject these formulations for gods because there is no better reason to think that they are real than to think they are not.
Of course, I know that theists will entirely reject falsifiability as a concept when it comes to their gods because theists are not interested in whether their beliefs are factually true or not, only whether they make them feel good. I think that all skeptics need to be well versed in this concept though, it’s a great test for many of the absurd woo claims in the world, if you cannot come up with a way to falsify the claim, the claim is irrational and thus, can be discarded. Science, it works bitches.