I would like to put this foolish old shibboleth to rest once and for all. I know this is probably a vain hope. Old dogs may not learn new tricks, but they never forget their old ones. Still, with a sigh, I will try to make clear that the concept of supernatural itself is meaningless.
We start with the word. What does it mean? As an adjective it simply means above or beyond the natural. From the Oxford Dictionaries more specifically:
Before that we must next ask what it means to be beyond the laws of nature. Nature as a word has many meanings, and this can obscure rather than clarify.
I submit that for this discussion it does not mean
- the phenomena of the physical world collectively, including plants, animals, the landscape, and other features and products of the earth, as opposed to humans or human creations
- the basic or inherent features, character, or qualities of something: (informal) the inherent and unchangeable character of something.
Therin lies the problem. Whenever somebody talks affirmatively about souls, or ghosts, or gods, or spirits, or anything else that gets lumped under the term supernatural, they always end up ascribing an actual nature to them. They have to. This is what it means to describe things that way. So when they claim that someone they know is a real fortune teller, they are saying that it is in that person's nature to transcend the arrow of time to have experiences of the future in advance. When they talk about a god, they might start by claiming it is essentially unknowable. They will strongly suggest that it is impossible for the deity to be constrained in any way. Yet saying this god is unconstrained by nature, is the same thing as saying that it doesn't have a nature of its own. There's no way around this. To have a nature is by definition to be constrained. At heart believers know this to be the case. In any conversation with someone who believes in a god they will eventually make explicit claims about what that god's nature is and isn't, what that god does and does not do.. Make an assertion counter to their account, and they will correct you instantly. They will say, sure, god can be anything, except that. The same is true for believers in ghosts and psychics, immaterial souls. For the believer, these things can be expected and eventually observed to behave in particular ways and not in others according to the nature of what they are. In the end to be knowable is to have a nature, Supernatural is a useless term.
Which returns us to the idea of something "beyond scientific understanding". As long as your goal is to determine what is the case, you are inquiring after the nature of things. Once you expect to observe something behaving in a particular way, you have exited the realm of "other ways of knowing", and fully entered the realm of science. That is the problem with the doctrine of knowledge by faith which asserts that there are two spheres, one where things can only be known through reason, evidence and sound epistemology--science, and a second where you can know things in some other way without those requirements. This assumes we have the capacity to tell the difference. It would not work otherwise. Without being able to tell which approach to use in a particular case, we end up just guessing and hoping. I can report that have found no evidence for such a capacity within myself. I don't think it exists in others. However, even that might not be important in the end. If science is what we use to vet claims about the nature of those things expected to have observable effects, the only thing we have left to vet by "other ways of knowing" like faith are things without a nature of their own which are not expected to have observable effects. I can't imagine what such things would be. How would we attempt a conversation about them? For all practical purposes this sounds like a null set.
So this insistence that true critical thinkers must admit to the possibility of the supernatural is at heart bogus, because the term is empty. Supernatural is an abstract point of departure that one has to retreat from the minute any meaningful conversation starts.