The supernatural exists.

Proving a negative is not demonstrating your claim. You have the burden of proof so you need to make the positive claim. But I don't care I want to debate anyway so I'll take a stab at it. You start by saying "Naturalism (the view that only the natural exists) is self-refuting because it undermines the necessary preconditions for rational thought and justified belief, including whatever line of reasoning lead to belief in naturalism. If we are in fact rational and justified in at least some of our beliefs, then some version of supernaturalism must be true." So what exactly are the necessary preconditions for rational thought and justified belief? Oh you didn't explain that? Because you certainly smuggled in the idea that our rationality is only explained by some version of supernaturalism. You need to demonstrate what the necessary preconditions for rational thought are. Technically defending naturalism is not my burden as I'm rejecting the supernatural, but I will. I'll also accept your definition of naturalism being the view that only the natural exists, but that the natural includes physical reality and constructs contingent on physical reality. So things like rationality are not physical, but that certainly doesn't mean they're not natural. Rationality and justified thought are contingent on the physical brain, therefore we have no reason to believe that justified belief or rational thought are products of the supernatural. You said "thinking through a line of reasoning... is directly caused by the underlying chemical activity in our brains which happens deterministically according to the laws of nature."" This seems like a free will argument. I don't totally disagree with the idea that we are subject to our brain chemistry, but you're only referring to the proactive behavior of the brain. You're forgetting its ability to react to stimulus. Seeing as there are countless non-deterministic stimuli like sound and light, the reaction to these stimuli couldn't be predetermined, because of the different ways the brain has to react to different stimuli. Sure your brain "fizzes" in a general manner as your genetics dictate, but because of non-deterministic input into to the brain, the brain can not pre-determine what the input will be, thus the brain's reactions are not predetermined. Beliefs are products of information input. Yes, information is natural as it is also contingent on the brain. So if you teach a kid there's a magic man in the sky who cares if you're good or bad (santa clause on christmas eve flies in the sky) and their brain reacts to this input in a way that makes sense for the kid, he may believe it. Regardless, this belief in santa clause couldn't have been produced with just the kid's brain chemistry alone as there was no way to know about santa without the non-deterministic santa information being input into their brain by you. You then say "So even though our beliefs are caused by blind mechanistic events in the brain..." Can something blind react to light? Ok, then brain mechanisms that react to light are not blind. We observe things by using light, and our observations develop our beliefs. You then claim "Under naturalism, it isn't possible for your beliefs and desires to affect your behavior." Ok, so like with the kid example, on christmas eve, the kid decides to go outside at night and look for santa clause. Would the kid go outside to look for santa clause if he never believed in santa? This is how it's possible for his belief, a product of a reaction to natural non-deterministic informational input, to affect his behavior. You say "So if naturalism is true, we should not expect to have developed the capacity for arriving at true beliefs. That makes naturalism self-refuting." Nope. Arriving at true beliefs requires the brain's reaction to non-deterministic informational input of truth claims and observations of non-deterministic physical occurrences. So as the brain's activity is differentiated to manage differentiated stimuli/information, so are people's beliefs. Arriving at true beliefs happens when someone can demonstrate the belief, replicate it, and use the demonstration and subsequent replications to make accurate predictions within the subject area of the belief. It's definitely not pre-determined by the brain. I agree that false beliefs like true beliefs require brain chemistry, but true beliefs aren't created in brain chemistry; they're a result of a constructive process that we use to determine if beliefs match with reality or not. This process is contingent on the brain, making the process natural. Our beliefs then inform our actions, so if we believe more true things and fewer false things then we're more likely to act beneficially to our longevity and not counter to it. You say "The problem, though, is that for any true belief one might think is adaptive, it's trivially easy to think of a false belief that would do the same thing." And I agree. I just think that the false beliefs that lead to adaptability are the exception...a small exception. So that overall vastly more true beliefs yield adaptability than do false beliefs. So I reject supernaturalism, because you have not demonstrated anything supernatural, you've only attempted to negate naturalism, which you misrepresented, and you've been corrected in your errors. -Naturalism is the natural + the contingent on natural. -Brain chemistry has to react to non-deterministic stimuli accordingly therefore it is not deterministic. -Beliefs require informational input into the brain that is subjected to a constructive process that attempts to match a belief with reality. -Our beliefs inform our actions and are ever intertwined. A child who didn't believe in/didn't know of santa clause would not look in the sky on christmas eve for santa. A child who does believe in santa might. Beliefs-->Actions. -Yes false beliefs can lead so success, but overall way more true beliefs result in successes than do false beliefs, that it's simply better to believe true things based on the much higher probability of a true belief leading to success/adaptive behavior/etc.. Please present a demonstration of something supernatural, and provide evidence for it, not evidence against it's contrast.