"A Priori belief in the non-existence of the supernatural (is that a fair definition, btw?) can easily be characterised as bias, or as something requiring evidence. In that sense it shifts the burden of proof from theists (where it should be) to atheists."

Oh, it is bias, but it's bias that is accompanied with a change in definition for so-called "supernatural" phenomenon so that they fall under the "natural" label. Well, mostly.

God is tricky, but to get around the burden of proof that you claim pops up, I'd say that I'm not claiming that God does not exist (I'm really not), I'm just shunting His characteristics OUT of a category which for all intents and purposes cannot affect us.

I don't claim to know anything about God, as it's up to the individual theist to define their deity any way they want. If they can't make the claim, I revert to the null hypothesis of non-existence, and I don't believe that it exists (which is different, of course, to believing that it doesn't exist).

"To get around this, I subscribe to a kind of functional naturalism, or maybe you could call it scientific naturalism, where I rely wholly on scientific thinking to explain the natural world, and define the supernatural as the point at which the scientific method breaks down."

When someones says something like "the point at which the scientific method breaks down", you really have to think about what that actually means. Why would it break down? I'll leave that to you to come up with an answer for that, because I want to hear what you have to say.

"Under this definition I think it is theoretically possible to have intrusions of the supernatural on our natural world, particularly if you start considering a nature-controlling God. Genuine miracles would be a good example."

Again, my reply to this depends on your explanation of "science breaking down".

Cheers,
Jack

Of course, I agree that their use of these pieces of equipment are unjustified, ie. they've never had a gold standard of "ghost" to draw expected data signals from, but the point is, if they did have such a standard, they could scientifically test ghosts.

I think the mechanisms behind the interactions with the natural world do not have to be explained BEFORE a search commences, but it's reasonable to expect/demand that some hypotheses could be drawn up beforehand and tested against the data. Good science should be able to be done. It's clearly not being done at the moment.

Plus, keep in mind that I don't think ghosts really exist. ;p But people making the claim that they do have no excuse for a lack of evidence.

It's a nice analogy you've drawn between God and His creation, and an author and their characters. This may in fact be a true description of reality. However, it's an unfalsifiable one.

How are we to know if this is the case, that God is the author of reality? While His actions do affect the physical world, by the very way you've set up the analogy, they affect it in a way that is not detectable: reality could proceed in exactly the same way without a God. Adding a God into the equation does not alter anything, unless that God intervenes in ways that are not consistent with what we would expect the world to do by itself.

Unfalsifiable ideas such as this may have emotional benefits (eg. "God has a plan for me"), but ultimately, they don't advance our understanding of reality at all.

Cheers,
Jack

But in relation to the ghost aspect, so-called ghosthunters arm themselves with tons of electronic equipment with the a priori belief that all of it can actually detect ghostly phenomena, whatever they may be. Why a thermal imaging camera detects a ghost's lack of body temperature, no one seems to know. Believers assume ghosts must be miserably cold entities. So, ask a ghosthunter how ghosts can be both supernatural and detectable in the natural world, and you'll likely get double-talk for an answer.