One bit of philosophy that some paranormal researchers like to trot out is about white swans. Briefly, it says that if you see lots of white swans you might reasonably conclude all swans are white, until you see a black one (for a rather more rigorous version see here). Note: for the sake of argument, let's ignore the fact that we know there are black-necked swans, black swans, etc.
As a bit of philosophy or logic it's fine. If you discover an exception to the predictions of a scientific theory, you must reconsider the theory. The problem is that some paranormal believers use the logic inappropriately.
For instance, you can't claim you've proved that not all swans are white just because you once saw a 'black one' on a wet, dark night (which, on investigation, turned out to be a grey cygnet). Or you took a photo of a black swan in the distance (which, on investigation, was found to be because the photo was lousy and the swan dirty). Unfortunately, that's often the type of evidence we often have to deal with in the real world.
Another application of the 'white swan rule' really irritates me. It is when you explain, in huge technical detail, why orb are, in fact, a bit of dust, out of focus and caught in the camera flash. Then they'll say, 'yes, I understand all that but MY orb was different!'
Karl Popper used the white swam example in his Philosophy. Few read it, as originally proposed, and even fewer read the more modern takes on it.
It's a logical principle (revolving around falsification) that nothing can be proven 100% as one always has to be prepared for the chances of a counter-example - even if it has never happened in the past and appears so unlikely to happen in the future. So it provides qualification for thinking.
This in itself is misunderstood by the woo-woo as implying that science is 'weak' or 'wrong'. They don't understand inductive science and logic.
It is the generic lack of understanding of logic that frustrates me the most - which i think underlies most, if not all of the frustrating examples you could think of....
Last edited by Dr B; 2nd November 2007 at 11:19 AM.
Here is a rather basic frame of reference to your swan story. When I was around twelve a friend invited me into her house. I thought is was all very strange because there was no yelling or banging doors or screaming. I thought they were weird. They were my black swan. My life was never the same because I knew there must be more black swans out there, and that there was more to life than white swans.
Parable of the Cave by Socrates ??
http://www.bulldognews.net/cave-parable.html
Here is a brain teaser for you. Someone on another forum said he / she did not understand the phrase "you cannot prove a negative" in science.
They went on to give an example which went something like this: "If I am in my house, with my pet cat, and we are both in the kitchen - I have proven that the cat is not in the bedroom - thus proving a negative"
Logically this is not true. The example is only positive evidence for the cat being in the kitchen (not negative evidence pertianing to the bedroom). This makes it unlikely that the cat is in the bedroom at the same time. But this example / observation does not prove it so 100%.
Now - there are some interestring further discussions about what the phrase "proving a negative really means" - but I just wanted to deal with why, in this example, the negative has not been proven at all.
Again it is a logical position which helps with casting information in the right manner. There is not always a binary relationship between 'showing A' and 'not showing B'
It's all about understanding the nature of evidence (what is necessary and sufficient) and the qualifications it requires.
Originally Posted by Dr B
Pray, continue.....
I may have to disagree with you.
If the claim was "the cat is not in the bedroom" the cat can only be in or not-in the bedroom and providing contradictory evidence to the cat being in the bedroom, i.e. "the cat is in the kitchen", does indeed prove the original claim.
Of course a cat is a tangible entity. It's intangible or universal negatives that cannot be proven. If something doesn't exist it's impossible to prove it doesn't.
.
I'm with John here. It is possible to prove specific negatives, it is only negatives in general that cannot be proven. This is usually simply because there is such a large, often infinite, possibility space which needs to be explored in order to do so. For example, if I say that no-one has green hair, I need to examine every single person in the world to prove this. On the other hand, if I say no-one in my house has green hair, I only need to examine myself to prove it.
"You can't prove a negative" is only a general guideline, it isn't a universal law.
Showing the cat is in the kitchen does not speak as to whether it is in the bedroom (or anywhere else for that matter). It only shows that the cat is in the kitchen.
While one can make a reasonable extrapolation from this - with more obscure areas of science this causes problems - so it is best - in all circumstances - not to make a habit of it.
This is not proving a negative - it is positive evidence for the cat being in the Kitchen - it is thus - positive evidence for the whereabouts of the cat.
Maybe the cat is the master of the universe and can be in two spaces at the same time- thus being in the kitchen is not negative proof against the possibility of it being in the bedroom per-se.
As I said above - we can of course make the reasonable exptrapolation that as the cat is in the kitchen, it is unlikely to be in the bedroom as well - but this observation is not negative evidence for this conlcusion - it is positive evidence for the conclusion "the cat is in the kitchen". One can certainly re-frame it to make more sense - but my point is - in the example provided by the other person - the type of conlcusion (proving a negative) does not necessarily follow from the type of observation. This is really only a problem for the more inductive areas of science.
I would be happy to accept the conclusion that the cat is not in the bedroom (or unlikely to be in the bedroom) but this is based on the positive evidence of it being elsewhere....
Therefore - for me at least, this does not prove a negative. Whether one can prove a negative is another matter.....
Last edited by Dr B; 2nd November 2007 at 01:12 PM.
I think you will find this is consistent with everything I have said.
I agree - and have added some extra comments above that clarify it."You can't prove a negative" is only a general guideline, it isn't a universal law.
But you are re-framing the issue - which as I have stated above is easy to do. But I never argued against that re-framingIf the claim was "the cat is not in the bedroom" the cat can only be in or not-in the bedroom and providing contradictory evidence to the cat being in the bedroom, i.e. "the cat is in the kitchen", does indeed prove the original claim.
Somewhat circular?It's intangible or universal negatives that cannot be proven. If something doesn't exist it's impossible to prove it doesn't...but i know what you are getting at
The cat is a quite unnecessary complication.
I might just as well say "I am in the kitchen, therefore I am not in the bedroom".
In any case, that example is a deeply individual-and-time-specific one. the fact that I (and/or a specified cat) currently reside in the kitchen is no evidence that we cannot be in the bedroom at some future time, or cannot have been there at some past time, nor that some other human and/or cat cannot be in the bedroom now or at any other time.
It also depends on a spatial arrangement that precludes someone being in both locations, either by an individual spanning two distinct yet sufficiently adjacent locations, or by one location being enclosed within the other (bedsit or tent, anyone?).
Even in general, with individuals generally being rather smaller than the universe (omnipresent deities excepted), information about where they aren't is generally vastly less use than information about where they are.
If I go into the bedroom and the cat isn't there, have I proved a negative then?
What if you set up CCTV in the bedroom and watch it with the cat on a monitor from the kitchen?
I'll get my coat
I think it may rather depend on whether the cat wants to be found.
Brief thought: the distinction that is wanted here is not between the general and the particular but between the universal and the individual.
(x)( Fx > Gx)
is equivalent to
~(Ex)( Fx.~Gx)
The first is a universal quantification; the second is the negation of an existential quantification.
Ummm... " If it's an F, it's a G" is equivalent to " There is no F that isn't a G". If you can't prove one, you can't prove the other. It's quite right that what can't be proved is not a negative ( as such) but a universal. But universals can always be expressed as negative existentials- whence " you can't prove a negative".
I can't resist commenting on the Cat Question. If there's a cat in the bedroom and a cat in the kitchen, there are two (2) cats, not one (1). Trust me. :-)
as I have said above, more than once, one can 'play' with it to make it make more sense - but this was not the claim posed by the other person. My points were only ever restricted to the initial example - where a specific claim was made on a specific type of observation.
This does not prove a negative
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