Essay:The supernatural can't exist II
 The supernatural
Claims about ghosts, the afterlife, psychic powers, or even spontaneous human combustion are often lumped under the term "supernatural". On its own, it's almost impossible to say what "supernatural" actually means. All we know is that it is somehow "beyond" or "outside" the natural world, and as such the actual definition is dependent on how we use the word "natural". Defining "natural" would be traditionally the first step, but running to possibly the most useful technique for this it's probably best to try rewriting all that without reference to the word "natural" at all. Or "reality". Or "real". Or even things like "material". A challenge indeed, particularly as "real" and "not real" have a strong level of salience with people, and to avoid them almost makes this argument seem like a simple tautology.
 Looking at the universe
Everything that is or was or will be is, in principle, able to be experienced by us. Only a handful of indiviudals (12 to be exact) have walked on the moon and know what it is like, directly, to experience walking in a space suit in a gravity field a fraction as strong as on Earth in an atmosphere that barely registers as existing. Yet they experienced it, and it wasn't beyond the human race as a collective to do so. No one has yet walked on Mars, but that experience is too within our grasp. Orbiting Alpha Centauri would be another experience, if a little further from our practical grasp, but still within our plausible and fathomable ability. We can, however, codify what these experiences are and examine them through less direct methods. We can measure the gravity field of the moon and Mars with probes, detect the contents of their atmosphere with a spectrometer, and roll robotic probes across their surfaces and beam back the exact same raw data a human would collect with their own eyes and more. This might be considered "indirect" because people weren't actually there, but really there is no line between "direct" and "indirect" observation. You can look up at the sky, but you're not directly seeing the sky; you're instead actually seeing photons reflected down and scattered by the molecules in the atmosphere, that then must be focused by your eyes onto a retina, where a chemical reaction sends a cascade of impulses of relative polarity (caused by the motion of potassium, sodium and chloride ions across a membrane barrier to generate a potential difference) down a nerve fibre all the way into your brain where... well, this is where it gets complicated because it's not like "your visual cortex tells you what it looks like" or something like that because your visual cortex is part of you. Anyway, next to all of this, what is one more step? We're often told by people how we can't "see" atoms, but clearly what is the actual difference between looking at patterns induced on a computer monitor by their presence and seeing them supposedly "first hand" by photons that were scattered off them.
In short, we build up a model of our universe by sensory input. It doesn't matter what the cause and effect that leads to that is because ultimately it's all secondary and indirect. The Large Hadron Collider is just as legitimate a way of looking at and proving the existence of high energy "invisible" particles as staring at a cup (and the photons bouncing off it indirectly into our eyes) is a legitimate way of proving the existence of the cup. We can rationalise the cause and effect preceding this input reaching our senses how we like, what matters is that this sensory response and how our expectations of it are changed by the model we build of the world.
 If it's beyond the universe
Although defining "supernatural" in a non-arbitrary way is somewhat difficult, we can look at how it's actually used, which serves the purposes here just as well. In fact, how it's used is ultimately more important than anything like its strict definition. Most commonly, it is used as a catch-all term for something that is beyond science, or beyond observation by any of the indirect methods we have available to us. People would like the supernatural to be observable like that, hence the field of parapsychology and the Ghost Hunters, but then that opens it up to scrutiny - and while the trappings of a cargo cult science are present in parapsychology, "supernatural" is still the get-out-of-jail card for when we don't end up conclusively proving that someone has psychic powers. If it doesn't appear in our observations, we have a situation not a million miles The Dragon in My Garage as told by Carl Sagan. We should, rightly, discard anything that doesn't produce a sensory experience as meaningless and inconsequential. If something doesn't produce a sensory experience then it cannot affect us - for instance, a ghost doesn't really give us a sensory experience, but the belief in them or the fear of them might should we enter a purportedly haunted house. We therefore need to carefully examine our expectations of what this sensory response is and how it changes in order to differentiate between something affecting us and our mere belief in it affecting us. One of the more succinct phrases for differentiating the Thing itself and merely believing in the Thing goes along the lines of "reality is what doesn't go away when you stop believing in it". So whether it be gods or ghosts, we need to think carefully about what in the world would not change if we were to cease our belief in them. This is perhaps the root strength of skepticism: being able to observe in a state of disbelief, to see the world for what it is and not what you believe it is.
If it can produce a sensory response then we can begin testing it - we can ask under what conditions it ceases to produce that response (again, it doesn't matter if we use our own eyes, a computer monitor or some other technique because they're all equally valid as indirect methods) or under what conditions it changes to a different sensory experience. By playing with these conditions we can differentiate between something being consequential to us and our beliefs making us feel that it's consequential - because the most succinct definition of "real" available is probably "that which doesn't go away when you stop believing in it".
Whether we like it or not, what we tend to call "reality" will most easily be boiled down to "a series of sensory experiences". Things that produce such experiences are "real", things that don't "aren't real" and are inconsequential.
 Prayer; you cannot have it both ways
When someone uses the term "supernatural" they are attempting to have it both ways by saying that something is beyond science to measure but their pet idea still "real" - but science is nothing more than building up a model of the world based on what does and what does not produce sensory experience. They ask for us to believe in something as "real" despite it invalidating the criteria of "producing sensory experience" - again, a belief in something might produce sensory experience but this is not the same thing. On the surface, this seems to be a mismatch in how people are using the word "real"; the believer has a definition of "real" that goes beyond the skeptic's and does include things that don't produce sensory experience. We can avoid this little semantic problem by merely avoiding the term "real" and stating that the believer is asking us to believe in something that doesn't produce a sensory experience (hence why the argument may seem tautological) but with the additional assertion that it is still consequential. Something that is truly beyond science to measure is something that does not produce an expectation of sensory experience of any kind - yet so many things that are said to be beyond science do suggest an expectation of sensory experience. If we pray for someone's health we expect that they get better at a rate outside the usual random chance or regression to the mean. If we pray for money we expect a cheque in the post at a rate higher than the prior odds of the tax office offering you a rebate. We see a paradox where actions don't quite match up to what someone seems to believe. No one prays thinking that "prayer is not real, so won't produce any kind of measurable response" - yet if asked if science can measure prayer that is exactly what they will turn out to think. The sheer quantity of cognitive dissonance present in this piece of doublethink is mind-boggling to the skeptic. It will probably continue to be dismissed as prayer "being beyond science to measure", but this doesn't alter that when you strip it back to what it actually means you get a serious contradiction.
These are all things we can measure precisely because we expect an experience of them and can examine that experience. If we do not expect a response, then they are beyond science to measure - and they are not consequential to us. It doesn't matter what we do, the experience will not change. If you pray you get what you want at the statistical rate, if you don't pray you get what you want at the statistical rate. No change is reported in experience, which is what someone means when they say it's outside of science to measure, so the phenomenon can safely be ignored. If we don't reject beliefs that are inconsequential to our experience, then they risk wasting our time or worse, leading to consequences due to the belief itself. There have been plenty of recent cases where people have died because they put their trust in faith healing, which is a sensory experience expected of believing in magical healing powers that has no sensory experience themselves.
The trouble is that believers really do fail to realise this and continue with their doublethink. If they merely stopped saying "my woo is beyond science's ability to measure" and actually said what they supposedly mean, they'd realise it was also beyond their ability to experience it and be affected by it too. And something that is beyond your ability to experience is... fuck that rationalist taboo for once, I'll use the word because it has some solid salience; NOT REAL.