**From:** David Hart (*dhart@atlantisblue.com.au*)

**Date:** Sun Sep 11 2005 - 22:25:19 MDT

**Next message:**Ben Goertzel: "RE: Hempel's Paradox"**Previous message:**Jeff Medina: "Re: Hempel's Paradox"**In reply to:**Jeff Medina: "Re: Hempel's Paradox"**Next in thread:**Richard Loosemore: "Non-black non-ravens etc."**Reply:**Richard Loosemore: "Non-black non-ravens etc."**Messages sorted by:**[ date ] [ thread ] [ subject ] [ author ] [ attachment ]

Jeff Medina wrote:

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

of objects (all objects on Earth), finding non-ravens (of any color)

certainly provides information about the relative abundance of ALL

ravens (i.e. the probability that any given sampled object is a raven),

however stating that finding non-black non-ravens increases the

probability of the hypothesis "all ravens are black" strikes me as

sample double-dipping -- only the discovery of a non-black raven could

decrease P( is_black(x) | is_raven(x) ) -- I don't see how the discovery

of any non-ravens, of any color, should increase P( is_black(x) |

is_raven(x) ), particularly given the is_raven part. Where probability

mathematics is concerned, I'm a near lay-person, so a step-wise

explanation would be good!

David

**Next message:**Ben Goertzel: "RE: Hempel's Paradox"**Previous message:**Jeff Medina: "Re: Hempel's Paradox"**In reply to:**Jeff Medina: "Re: Hempel's Paradox"**Next in thread:**Richard Loosemore: "Non-black non-ravens etc."**Reply:**Richard Loosemore: "Non-black non-ravens etc."**Messages sorted by:**[ date ] [ thread ] [ subject ] [ author ] [ attachment ]

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