I was having a discussion with a Christian friend of mine the other day about mind-body dualism and something struck me about the idea. He seemed to be defending it (note: he isn't a staunch dualist, he is undecided) primarily because it is unfalsifiable. This violates all my ideals about how to determine what is true and what isn't.
I put forward the idea that all our observations about the mind indicate to us that it an emergent product of a complex brain. As brain complexity and size increase, cognitive ability increases as a general rule. Compare a fish to a rat, a lizard to a dog, compare a cat to an Orangutan, or a Lemur to a Human. Complexity and brain size directly correlate to mental power, and self-awareness is only apparent in those of the animal kingdom with particular large and complex brains.
My friend then said, that the evidence may suggest that, but it doesn't and cannot rule out that the capabilities of a disembodied mind run alongside and parallel to the physical brain. I was almost speechless, I cannot fathom how anyone could possibly consider that to be an argument for the validity of dualism. The evidence at hand does not point towards something, but because it cannot in principle rule out the mystical explanation doesn't mean that it is a credible answer.
The same principle can be applied to supernaturalism, gods, theistic evolution and any superstition imaginable. Any idiot can come up with ad hoc [ir]rationalisations as to why their belief is still true despite having no supporting evidence.
Say for example someone believes that a black cat crossing your path causes misfortune, and hears that you were in a car accident. They say to you "It must have been because a black cat crossed the path of your vehicle". You reply to them explaining that it was actually because your tire blew out, and caused you to lose control of your car, and that you didn't see any black cats. They then say "Well the tire blowout was cause by a black cat crossing your path, but it was hidden from view, so your crash was still caused by the black cat". Baffled by the inanity of what they're saying you reply and say "Well there is no evidence suggesting that your idea is even remotely true, so I'll stick with a plausible natural explanation". They then proudly state "So you admit you can't prove me wrong then? I'm justified in my belief then".
The only place this analogy breaks down, is that black cats do in fact exist. We have not even established the existence of gods, disembodied minds or a supernatural realm. Besides that fault, this analogy seems entirely accurate to me, and reveals the stupidity of holding beliefs simply because they are unfalsifiable.