[QUOTE=davar55;314435]Science may be qualified by "appears to be", etc., but logic and philosophy (which is where these questions abide) are even more fundamental than science and should be even more rigidly examined and understood.[/QUOTE]

Agreed.

But you, for some reason, refuse to accept their logical conclusions if they present ambiguity, or they disagree with your personal presuppositions.

[QUOTE=davar55;314439]I wouldn't DREAM of doing that.[/QUOTE]

You did.

Just now.

[QUOTE=davar55;314438]Quantum Theory came up because it was claimed that QT implied
a non-zero probability for a god's existence, which I challenged.

It's called a Theory (like relativity) because it isn't proven,
in the same sense as the Pythagorean Theorem on the
Euclidean plane IS proven.[/QUOTE]

Very different domains.

Physics is trying to model the observable universe using mathematics as best they can. By it's very nature, empirical observation is inexact.

Pure mathematics is trying to prove some very hard conjectures -- and they sometimes do. But they have the luxury of absolute observation since it isn't empirical.

[QUOTE=xilman;314434]I'm not sure how much credence you place in the text above. Do you believe the material about the unicorns or are you merely making a rhetorical point?

Just because no-one has [b]yet[/b] seen unicorns, despite a modicum of effort, that isn't proof that they do not exist. Until recently no-one had seen evidence for the existence of a particle with the properties predicted for a Higgs boson. No-one has yet seen any evidence at all for the existence of either the axion or the magnetic monopole or the graviton, despite theoretical arguments that they should exist (or not exist, depending on the theoretician). Do you therefore argue that none of the last three particles exist? Would you have argued a few years ago that the Higgs didn't exist but have now (presumably) changed your mind?[/QUOTE]

I've been skimming and thus not particularly understanding the context.

I was also implicitly assuming that a unicorn, if it exists, is of the same size as us, to an order of magnitude, and thus its existence would be directly observable by our eyes and/or satellite cameras. The same is obviously not true of particles. (And, of course, if we don't agree on what a unicorn is, then my argument is rather useless, but I was assuming we could at least agree on that.)

[QUOTE=Dubslow;314417]We can see the moon quite clearly, and there certainly aren't any unicorns (flying, yellow, or otherwise) on it. If you want to be pedantic (rather the point of this thread), there have been satellites (and humans) who've looked at the back of the moon, and no unicorns were observed then. Having thus examined the entire surface of the moon, we can say with certainty that there are no unicorns on the moon.[/QUOTE]Your disproof is flawed. I'm not certain that we have seen every point on the Moon. But assuming we have it is easy to counter with the knowledge that the unicorns there are shy and hide from the cameras when the satellites are taking images. Satellites can't take images of the entire surface of the Moon at one single instant, we don't have enough satellites to do that, so the unicorns simply run away to another part that is not being imaged (because they are shy; see above) and prefer to stay aloof.[QUOTE=davar55;314433]No unicorn exists.[/QUOTE]Prove it. Absence of evidence is not evidence of absence.

[QUOTE]… (because they are shy; see above) and prefer to stay aloof.[/QUOTE][QUOTE][B][URL="http://www.imdb.com/name/nm0005239/"]Invisible Boy[/URL][/B]: [[I]after becoming invisible for a moment and reappearing naked[/I]] I'm invisible. Can you see me?
[B][URL="http://www.imdb.com/name/nm0000279/"]The Blue Raja[/URL], [URL="http://www.imdb.com/name/nm0000513/"]The Shoveller[/URL], [URL="http://www.imdb.com/name/nm0001774/"]Mr. Furious[/URL], [URL="http://www.imdb.com/name/nm0836071/"]The Sphinx[/URL], [URL="http://www.imdb.com/name/nm0000413/"]The Bowler[/URL], [URL="http://www.imdb.com/name/nm0000607/"]The Spleen[/URL][/B]: Yes!
[B][URL="http://www.imdb.com/name/nm0001774/"]Mr. Furious[/URL][/B]: Wow.
[B][URL="http://www.imdb.com/name/nm0000279/"]The Blue Raja[/URL][/B]: Two hands there, son.
[[I]Invisible Boy covers up[/I]]
[B][URL="http://www.imdb.com/name/nm0000413/"]The Bowler[/URL][/B]: Maybe you should put some shorts on or something, if you want to keep fighting evil today. [/QUOTE][COLOR=White].[/COLOR]

"No unicorns exist."

[QUOTE=retina;314448]Prove it. Absence of evidence is not evidence of absence.[/QUOTE]

Evidence of absence of what? Unicorns? But you first mentioned them,
without definition, so it's incumbent on you to explain what they are.
If they are "fantasy horse-like animals with a head horn", then they
don't really exist. Take out the fantasy word, and it's still the claimant's
responsibility to define the object in question.

We both I'm sure see the next step w.r.t. the non-existence of god.
It is a long step, I admit.

[QUOTE=chalsall;314440]But you, for some reason, refuse to accept their logical conclusions if they present ambiguity, or they disagree with your personal presuppositions.[/QUOTE]

This is undemonstrated.

[QUOTE=davar55;314459]"No unicorns exist."



Evidence of absence of what? Unicorns?[/QUOTE]Of course, that was the subject at hand.[QUOTE=davar55;314459]But you first mentioned them,
without definition, so it's incumbent on you to explain what they are.
If they are "fantasy horse-like animals with a head horn", then they
don't really exist. Take out the fantasy word, and it's still the claimant's
responsibility to define the object in question.[/QUOTE]Yes of course it is, since I made the claim, I have never denied that. But what I am demonstrating is that it is impossible to prove my claim false. This was in response to your statement that it is possible to prove god does not exist. If you can't even prove that unicorns don't exist then what hope is there to prove that god does not exist?[QUOTE=davar55;314459]We both I'm sure see the next step w.r.t. the non-existence of god.
It is a long step, I admit.[/QUOTE]A very long step indeed. An impossible step. Even in a finite place like to Moon we can't prove things don't exist. And now you want to prove something doesn't exist in the entire universe? Multiverse?

[QUOTE=Dubslow;314445]I've been skimming and thus not particularly understanding the context.

I was also implicitly assuming that a unicorn, if it exists, is of the same size as us, to an order of magnitude, and thus its existence would be directly observable by our eyes and/or satellite cameras. The same is obviously not true of particles. (And, of course, if we don't agree on what a unicorn is, then my argument is rather useless, but I was assuming we could at least agree on that.)[/QUOTE]Very well. Let us restrict our domain to biological organisms which are easily visible to the unaided human eye. Substitute "Wollemi pine" or "coelocanth" for "Higgs boson". Pick any organisms of your choice to substitute for the other three particles; the only requirement being that they have not been shown to exist to the standards required by professional biologists. Perhaps the yeti might reach that requirement? Tantalizing hints, a degree of biological plausibility but no carcass or even DNA samples.

[QUOTE=retina;314463]But what I am demonstrating is that it is impossible to prove my claim false. This was in response to your statement that it is possible to prove god does not exist. If you can't even prove that unicorns don't exist then what hope is there to prove that god does not exist?[/QUOTE]

But I have proven that "unicorns exist" is arbitrary, because the statement
is made without definition of unicorns or evidence that "they" exist.
And arbitrariness (i.e. emptiness of conceptual content) entitles one to
conclude proven falseness.

You did start to write "they" might be hiding, which is part of a definition.
But if your example is intended to demonstrate something impossible
to disprove, due to the lack of a definition of the thing in question,
you're up against a challenge proof which requires you to define your
terms. And once you define unicorn (or god) the statement becomes
susceptible to proof or disproof.