[extropy-chat] Atheists launch inquisition...

[Hal Finney]

Gennady Ra writes:
>  From the review by Craig Waterman of The Probability of God: A Simple 
> Calculation That Proves The Ultimate Truth by Stephen D. Unwin (E-SKEPTIC #3 
> of 2004. JANUARY 12, 2004):
> ...
> Through special pleading, Unwin begins by invoking an a-priori 50% 
> probability towards his god's existence by arguing that 50% is an expression 
> of maximum ignorance (p. 58). I found this position astounding. What of 
> other speculations? Are we merely brains in vats hooked to computers? Do 
> magic elves steal socks from the dryer? Do Space-Penguins live in the center 
> of the moon? Claiming ignorance, the author to be consistent would have us 
> assign an a-priori 50% probability that each of these claims is true.

I agree that this is a common error in attempts to use Bayesian-style
probability analysis, this notion of 50% representing "maximum ignorance".
For example, what is the probability that there is life on a planet
circling the nearest star, Alpha Centauri?  We have no idea!  Should we
say it is 50%?  But we don't even know if the star has planets, let alone
whether any of them are in a habitable region, or even what conditions are
necessary for the formation of life.  As the reviewer notes, you really
need to consider all possible situations and establish a probability
distribution over all of them.  In the end it is unlikely that any
particular situation is going to turn out to be at 50% probability.

Hal