Definition of physical

[BrianSoddingBoru4]

If something is sensory - if you can see it, hear it, taste it, measure it and so it - we can be pretty sure that it is a physical something. Things which are not sensory - i.e., you can't see them, hear them , taste them, measure them, etc - bear a startling resemblance to things which do not exist at all.

So, yup - I'm pretty comfortable with the definition: physical (adj): existant.

Boru

[BrianSoddingBoru4]

Hmm,Rob, do you think it would make sense if we called anything that can reflect light as "physical"?

We call these things 'mirrors'. I'm pretty sure there's no such thing as a non-physical mirror.

Boru

[robvalue]

Cheers Boru

Yeah... it seems sensible that would be the case, that a mirror-type thing would be physical.

The thing is... how could you ever establish the existence of a non-physical thing? Let's say we have done some measurements and there is some kind of effect that's unaccounted for. We've examined all known physical factors. Now what?

How can we know that the remaining thing isn't physical? How can we know it's not made of something, but just something that doesn't interact in ways we are used to?

It seems that "concluding" the effect is caused by something non-physical is necessarily an argument from ignorance.

I know theists are basically trying to say, "But magic tho! What if there's all this mysterious shit!" Yeah... but is this shit made of anything? If not, how did you determine that without using the argument from ignorance? Just because we can't yet "see" what it's made of, it doesn't mean we never will; and even if we never do, it doesn't mean it's not there either. Science neither needs to or desires to disprove such magical concepts, hence methodological naturalism. I honestly don't know what "supernatural" even means.

I was thinking about forces, such as gravity. I don't think you'd scientifically say such a force "literally exists", but rather it is physical objects acting upon each other. How, exactly, is probably ultimately unanswerable and beyond the scope of science. We can model as best we can.

[ignoramus]

Rob. What about dark matter?
When we don't know much about it other than it's needed via the maths to balance what we currently see in the cosmos.

Is dark matter physical? Alex? I don't think we can know at this stage?

The funny thing about God is that the universe acts exactly as one would without a God present...
In fact, if God did intervene in any intelligent way, it would throw red flags up everywhere.

[BrianSoddingBoru4]

I happily grant that some effects are mensurate but we don't yet know the physical cause of the effect in question. So what? Science is, by its very nature, provisional. If we find an effect without a cause, even after we've examined 'all known physical factors', it simply means that there's a physical factor we don't know about (I know this sounds like scientism, but it really isn't).

A good example of this would be the perturbation in Mercury's orbit. For a distressingly long time, the only explanation was a planet closer to the Sun than Mercury, tentatively called 'Vulcan' - some people even claimed to have seen it. It wasn't until General Relativity allowed the possibility of a massive gravitational field generating secondary and (I think) tertiary fields that the wobbling of Mercury could be accounted for without another physical body in the mix. But that doesn't mean that gravity isn't physical. We can feel it, measure it, determine its effect on other things with a great degree of accuracy.

Boru

[BrianSoddingBoru4]

Is dark matter physical?

Well, dark matter is hypothetical and - according to the hypothesis - yes, it is physical.

Boru

[robvalue]

Yeah, this is just the kind of scenario I was suggesting. Say we had no idea if dark matter was physical or not. How could we conclude that it is not? How do we eliminate all the ways things can be physical? We're simply assuming we know everything already, and shifting the burden of proof.

This is the game the religious sometimes play. They assume our current models know everything, then they postulate something it doesn't know. Wow, supernatural!

[Cyberman]

The funny thing about God is that the universe acts exactly as one would without a God present...
In fact, if God did intervene in any intelligent way, it would throw red flags up everywhere.

Exactly this. I've often said that I don't believe a god as usually defined can possibly exist in a universe like this. There may be some kind of generic god-like entities similar to Star Trek's Apollo, Q, or the animated Lucien from Megas-Tu, but they are only established to be god-like by contrast to the rest of the Universe which operates perfectly naturally.