Re: Hempel's Paradox

From: Jeff Medina (
Date: Sun Sep 11 2005 - 20:41:14 MDT

Hi, Ben. Fancy meeting you here. ;)

Jeff wrote, "The only assumption required is that our sample space is finite."

Ben replied:
>> Suppose you have a population of 10 birds of different colors,
>> and no other knowledge about the population.
>> If you sample one of the birds and find that it's a purple goose,
>> why does this count as information that all the RAVENS in the
>> population are black?"

Because it is evidence that [all non-black objects are non-ravens]. If
we know at least one raven exists, and sampling a non-black object
produces a non-raven on each of N sampling events, then with
increasing N comes increasing certainty that no non-black object is a
raven. And [no non-black object is a raven] is, of course, logically
and conceptually equivalent to [all ravens are black], given the tiny
extra assumption I left out earlier that at least one raven exists.
It's pretty clear to me that Hempel's paradox presupposes the
existence of its referents, but if you disagree and think it's a
sticking point, I'm happy to concede that a purple goose is only
evidence that [all ravens are black] if and only if there exists at
least one raven.


Jeff Medina
Community Director
Singularity Institute for Artificial Intelligence
Relationships & Community Fellow
Institute for Ethics & Emerging Technologies
School of Philosophy, Birkbeck, University of London

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