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  Topic: Uncommonly Dense Thread 3, The Beast Marches On...< Next Oldest | Next Newest >  
keiths



Posts: 2041
Joined: Jan. 2006

(Permalink) Posted: Oct. 19 2009,01:29   

Quote (Missing Shade of Blue @ Oct. 18 2009,22:48)
Keith:

Quote
Any potentially falsifying observation that turns out not to falsify the hypothesis has strengthened it, because there is now one less opportunity for it to be falsified.

As far as I can tell, the only necessary background assumptions are these:

1. Valid falsifying observations are possible in principle (though they won't be possible in practice if the hypothesis turns out to be true).
2. Nothing (including our own behavior) is systematically preventing such valid falsifying observations from taking place.


These are not the only necessary background assumptions needed for your general claim to be true. Think of Good's example again, except make it slightly less fanciful. Suppose my background theory tells me that if there is any species where all the organisms are black, then for some reason it cannot grow beyond 500 organisms. On the other hand, if some but not all the members of a species are black, it will grow to at least a million organisms. I also know that there are at least 100 million birds in the world, and they are randomly distributed (i.e. species are not geographically localized).

I decide to test the hypothesis "All ravens are black." I step out of the house and the first bird I see is a black raven. What does this do to my hypothesis? Plausibly (given some further natural assumptions) it disconfirms my hypothesis. If all ravens were indeed black, then it would be incredibly unlikely that a randomly sampled bird is a raven. On the other hand, if some ravens are black but all of them are not, then it's not that unlikely. Given my background theory, the observation of the black raven, a potentially falsifying observation, neither falsifies nor strengthens my hypothesis. It weakens my hypothesis. And this is the case even though I have not violated either of the two background assumptions you regard as sufficient.

You're right, my two conditions are insufficient to guarantee the statement as it stands.

There are really two competing things going on in your example.  The fact that the observation is non-falsifying strengthens the hypothesis, but the fact that the object is a black raven, given your background knowledge about the possible distributions, weakens the hypothesis more than it was strengthened by the non-falsification.

So to my two conditions you would have to add a third:

3. You possess no background information whereby certain non-falsifying observations would actually weaken the hypothesis more than they strengthen it.

--------------
And the set of natural numbers is also the set that starts at 0 and goes to the largest number.  -- Joe G

Please stop putting words into my mouth that don't belong there and thoughts into my mind that don't belong there. -- KF

  
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