Am 13.03.2012 19:52, schrieb Kevin Wampler:
> This is just off of the top of my head, so it may not coincide with the
> "accepted" answer to your question, if such a thing even exists. It's
> also not necessarily very well thought out yet.
>
As it is fun, a good exercise and I do have an ill cat sleeping on my 
lap (and therefor cannot stand up and go to bed) out of my head and 
based on my understanding from Kant to Popper a few remarks - with a 
high possibility of wrong citations ;)

> Anyway, It seems that something related to your question is the
> oft-mentioned quip that evidence can only disprove a
> theory, but never prove it.

Popper did say something like: "The purpose of evidence from repeated 
observations is not to confirm already-established theories, but to 
attempt to falsify them and thereby test them."
This is *a bit* different and better to understand when when we look at 
the scientific method and consider the following points:
a) It is easy to obtain confirmations of a theory if we look for them ;)
b) Confirmations should really only count if they are the result of 
*risky* predictions.
c) Every *good* scientific theory is a prohibition: it forbids certain 
things from happening. The more it forbids, the better it is.
d) A non-falsifiable theory is not scientific.
e) -> Every genuine test of a theory is an attempt to falsify it.


> In what sense can it be said that we have
> "evidence for" anything then? Obviously there must be some meaning to
> the phrase, since otherwise a theory which says "anything is possible"
> would be regarded as an ideal theory, since it's obviously never been
> falsified.

see c) above.

> The most obvious answer I can see is to consider the question from a
> statistical perspective rather than a perspective of pure deductive
> logic. In this viewpoint the predictions yielded by a theory would be
> interpreted as a probability distribution over (a subset of) observable
> events. The goal of a good theory should then be to make predictions
> which match the actual observed probabilities (and possibly satisfy some
> aesthetic criteria).

I have no idea what "aesthetic criteria" could have meaning here but 
anyway...
David Hume's point was: laws are general, and therefore apply to an 
infinity of cases, so no finite number of observations increase their 
likelihood by any amount.
But Emanuel Kant: In science, only observation and experiment may decide 
upon the acceptance or rejection of scientific statements, including 
laws and theories.
AFAIK Kant did not *solve* this logical problem but Popper did *avoid* 
it by stating: a scientific theory is tentative only (that is, all laws 
are only conjectures, not true generalizations).


> In addition, instead of talking about the merits of a theory by itself,
> I'll switch to the view that, strictly speaking, evidence can only be
> used to differentiate between different competing theories.

I do not think that a competing theory is necessary but we often have an 
*established* theory versus a *risky* new one:
Geocentric -> Copernican
Where the risky new one does not necessarily falsify the old one, it may 
only limit the scale where it is valid:
Newton -> Einstein


> In this view
> there are, colloquially speaking, *two* ways in which evidence might
> support theory A over theory B. Firstly, as in the logical case, you
> could observe something which theory B predicts is very unlikely or
> impossible, but which theory A give higher probability to. Secondly, you
> might find that theory B predicts more events than are actually
> observed, whereas theory A gives low probability to unobserved events.

In case of competing theories Occam's razor comes in quite handy.


> So what of your question then? Fossil evidence can support a theory like
> evolution in the case where evolution predicts a high likelihood of some
> events (like your fish example) which competing theories don't ascribe
> any particularly high probability to. For instance your basic
> intelligent design argument would probably give finding such a fish the
> same probability as finding countless other sorts of things which
> weren't observed.

Comparing "Intelligent Design" to "Evolution" is like comparing apples 
and eggs as the basic requirements for a scientific theory are not 
fulfilled by ID.
This is the basic misunderstanding when creationists call evolution 
*just* a theory. Yes, it is just a theory but this is its strength.
To state Popper again: "The point of the criterion of falsifiability is 
not to solve a problem of meaningfulness, or significance, nor truth, 
nor acceptability. It is the problem of demarcation between science and 
non-science."
And to leave this sad field of ID and make it maybe even a bit more 
provocative ;)
"The apparent strength of Freudian and Adlerian psychology, and Marx's 
theory of history, that they can explain anything is actually a weakness 
in contrast with Einstein's theory that took risks."
I'm not sure if this has actually been said by Popper but it very well 
might have.


> Of course strictly speaking we don't exactly have evidence "for"
> evolution (or whatever theory you like), just for evolution in favor of
> our ideas for currently competing theories. If some future theory makes
> even more precise and accurate predictions than evolution, then it's
> probable that this theory would also give a high probability to your
> fish example and thus the fossil wouldn't give evidence to evolution in
> favor of this hypothetical new theory.
>
This is exactly how the scientific method works.


> As an aside, the fact that you mention a case where the evidence was
> found *after* the theory was formulated is interesting. Strictly
> speaking you'd think it wouldn't matter when the evidence was found,
> just what that evidence was. Nevertheless, such examples are extremely
> useful because they help assure us that we haven't "cheated" and created
> a theory which is little more than rephrasing known evidence in a
> different way, as it's impossible to bake predictions into a theory if
> you don't know what these predictions should be. So I see this as more a
> vital psychological tool rather than something directly related to the
> theories themselves.
>
If you replace "psychological" with "philosophical" I might agree, 
partial...  my sentence above (about Freud, Adler, Marx and Einstein) 
goes in this direction.
Also note the interesting fact that contemporary "multi-verse", 
"gravity-quantum-loop" and "string"-theory also fall through the sieve 
when we look at them with Popper's theory about scientific theories in mind.
And dark matter and dark energy are at least very borderline. But, to 
me, this makes science currently quite thrilling ;)


> Does this make sense?
I think so even if that does not mean that I fully agree ;)

> I ask genuinely since I haven't really though much
> about it. I also suspect that you could draw some more rigorous ideas
> about the "aesthetic criteria" a theory should preferably satisfy by
> looking at information theory, but I don't care to give it a go at the
> moment.
Well, I for one would be interested in your "aesthetic criteria".


-Ive

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