From: Ivar Ylvisaker <ylvisaki@erols.com>
[...]
>[Richard Wein wrote:]
>
>
>> I don't agree with you. I think that in any inference of design where we
>> don't have positive proof (like having actually seen the object being
made),
>> we must use a process of elimination, and, beyond a certain point, we
must
>> simply say "We consider it inconceivable that any natural process could
have
>> created this object, so it must be designed." Suppose, for example, that
>> SETI receives an extraterrestrial message like the one in the book
Contact.
>> We cannot prove that the message was not produced by some unknown natural
>> process, i.e. in accordance with some unknown chance hypothesis.
>> Nevertheless, because we can't conceive of any natural process producing
>> such an effect, we reject all such unknown hypotheses.
>
>I don't agree with you. "A man made it" is a perfectly respectable
>hypothesis. Men (and women) called mathematicians did discover prime
>numbers (the initial signal in "Contact"). If signals containing
>prime numbers were detected from an extraterrestrial souse, the most
>reasonable hypothesis would be that man or, at least, something
>intelligent, sent them. We do not have to eliminate all natural
>processes to conclude this.
But suppose that we knew of a natural process that generates digitised
sequences of prime numbers in radio signals. Then we would not accept the
hypothesis of intelligent origin in this case (or at least not without
considering the natural hypothesis much more carefully). So, in accepting
the hypothesis of intelligent origin, the SETI researchers in Contact must
have implicitly ruled out such a possibility (or at least considered the
possibility so remote as to be insignificant).
>In any case, we can't; there is always
>the possibility that some natural process does generate them.
Yes, but I think we can say that we consider such a possibility to be
implausible. Now, if you ask me what is the intuitive process by which we
come to such a conclusion, then I will have some difficulty answering you.
Nevertheless, I think we do intuitively come to such a conclusion, for the
reason I've just given.
Of course, there are other situations where we can't think of a plausible
naturalistic hypothesis, but we also don't feel able to reject the
possibility that there may be one. In that case, we would have to just say
that we don't know whether the phenomenon had an intelligent origin or not.
And there are other situations where we only feel it's *improbable* that
there could be a natural explanation, and we conclude that the phenomenon
*probably* had an intelligent origin.
>Given
>our present knowledge and theories, an "intelligent being sent them"
>would be the current "best explanation" of signals containing prime
>numbers sent from Vega.
But why? What is the logical argument that leads to this conclusion? If you
simply respond that it's intuition (as I've done above), I will answer that
at least my argument gets us one more step down the road to uncovering the
logic of our intuition.
>This conclusion would be reinforced if we add
>the video of Hitler speaking at the 1936 Olympics -- apparently, it
>really was televised -- and the plans for an interstellar vehicle that
>followed in the signals that were received from Vega in the book
>Contact.
>
>Two other comments. "An intelligent being sent them" is "an inference
>to the best explanation" of the signals received in Contact;
I would suggest that, in the case the Contact signal, we would say rather
more than "best explanation". I think we would say "only conceivable
explanation".
>it is not
>a confirmation that intelligent beings did so. Someone had to go to
>Vega to confirm this. One can always hypothesize that an intelligent
>being secretly caused some event to occur, e.g., an evil spirit caused
>a cancer. Finding evidence that confirms this is the hard part. (See
>also the Concluding Comments in
>http://philosophy.wisc.edu/sober/dembski.pdf.)
But Sober's (Bayesian) position is a counsel of despair. He says that: "The
best you can do is compare theories with each other." With this approach, we
can never infer design, because we cannot consider all possible natural
theories. Yet, in the real world, we do make inferences of design.
>Second, Dembski specifically disavows that this is what he means by a
>design inference. He writes a little later in the reference cited
>above:
>
>"Thus, we shall never see a design hypothesis D pitted against a
>chance hypothesis H so that E confirms D better than H just in case
>P(D|E) is greater than P(H|E). This may constitute a "Bayesian
>design inference," but it is not the design inference stemming from
>the Explanatory Filter."
Yes, I agree that Dembski's inference is not a Bayesian one.
The approach I described is not a Bayesian one either. It rejects the
possibility of a natural explanation on the grounds that we cannot imagine a
plausible one, not on the grounds that we consider all such explanations to
have lower likelihood than the design hypothesis. But perhaps my approach
should be made into a Bayesian one, by arguing that, when we infer design,
it's because we intuitively feel that there could not be a natural
explanation with greater likelihood than the design hypothesis.
By the way, in my rebuttal of Dembski
(http://website.lineone.net/~rwein/skeptic/whatswrong.htm), I deliberately
rebut him on the non-Bayesian turf that he has chosen. ;-)
>He seems to waver a bit about this conviction in his "Intelligent
>Design" though the book still contains a description of the filter.
>See "abduction" in the index.
I haven't got "Intelligent Design". Perhaps you could quote me the relevant
passage, if it's not too long.
Richard Wein (Tich)
--------------------------------
"Do the calculation. Take the numbers seriously. See if the underlying
probabilities really are small enough to yield design."
-- W. A. Dembski, who has never presented any calculation to back up his
claim to have detected Intelligent Design in life.
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