>
>How much evidence do we have for extraterrestrials? for purple people
>eaters? for men on mars? Do you think they are there?
>
When Richard Dawkins is confronted by this argument, he responds as you do,
except that he uses fairies and unicorns. What both you and he fail to
understand is that there are good theoretical reasons for why
extraterrestrials, purple people eaters, men on mars, fairies and unicorns
cannot exist. These reasons may one day turn out to be wrong, but at least
they are good positive reasons for claiming that these concepts are not
real, rather than being poor negative reasons like a lack of evidence.
>
>At some point the lack of
>evidence does influence you in your thinking (unless I miss my guess).
>
The lack of evidence certainly can allow one to disbelieve that a concept is
real, but that's not the same thing as proving the concept false. That's
where I believe you and Dawkins make your mistake, scientists though you
both are. The reason why the appeal from ignorance is a fallacy (and thus
_a priori_ false under any set of circumstances) is because it is impossible
to either prove or disprove (or, if you prefer, verify or refute) a concept
based solely on a lack of evidence. That's no different from armchair
theorizing; both violate the basic tenet of science, which is that evidence
determines what is true and what isn't. Hence even if you are trying to
refute a concept you need to provide evidence that shows that the concept is
not possible. That's why I asked you if you had any theoretical reasons why
there cannot be any Cambrian ancestors and what evidence do have (other than
a lack of fossils) that supports these reasons, two questions you ignored.
>
>At
>what point is that? Would it be when a hundred years of intensive
>searching in the fossil record has yielded nothing?
>
Funny, Duane Gish asked me that very same question a couple of years ago,
when he and I were debating the existence of transitional forms. We were
talking about birds at the time, and I had told him that the lack of
transitional forms (i.e., a lack of evidence) between modern birds and
Archaeopteryx did not prove that birds had not evolved. He responded by
asking me what my opinion would be in a hundred years when an intensive
search of the fossil record turns up nothing. I told him my response would
be the same as now, that a lack of evidence cannot prove the concept false,
and to claim it can is to engage in a logical fallacy. He never responded.
Of course now the whole point is moot; avian transitional forms have been
found, which underscores the inherent weakness of arguments based on a lack
of evidence.
To answer your question, however, as a good scientist there should never be
a time when I would allow a lack of evidence to convince me that a concept
is false. Only if there were good theoretical reasons why the concept must
be false would I accept that conclusion in the absence of evidence.
>
>When the rocks in the
>Precambrian are in every point just like those in the Cambrian, but without
>fossils?
>
Are you serious? The Precambrian covers some 3 billion years; are you
suggesting that at every point throughout the Precambrian throughout the
world the conditions were identical to those in the Cambrian, which itself
lasted some 70 million years and had a wide variety of different
condistions? Are you suggesting that that the igneous and metamorphic rocks
that dominate huge areas of the Precambrian are similar to the sedimentary
rocks that dominate huge areas of the Cambrian? I think you are grossly
oversimplifying things here.
>
>When soft-bodied forms are found in abundance in the Earliest
>Cambrian? There is no reason given the naturalistic presuppositions that
>there should not be fossils in the Precambrian.
>
There are Precambrian fossils. The crossover from Precambrian to Cambrian
occurred at about 545 million years ago; the Ediacaran fauna first appeares
in the fossil record around 600 million years ago, well into the
Precambrian.
>
>What is true for the Late Precambrian must be true for the Early Cambrian
>as well. (It is profoundly not).
>
Why must it be true? Depending upon how you define "early" and "late" you
could be talking about a period of as much as 80 million years, if not more.
Even if you arbitrarily restricted this period to as little as five million
years there could still be profound changes in climate, population sizes and
faunal diversity during this period. I find it a bit arrogant to claim that
all these factors must remain unchanged over such a long period of time,
especially when the available evidence demonstrates otherwise.
>
>>Maybe the descendents migrated into that area from
>>somewhere else where they evolved,
>
>Where might that have been? and with such a variety of forms, why were
>they unable to migrate erlier, an why were they all contained in that place
>or places?
>
>>and maybe the sediments of that other
>>place no longer exist or are currently inaccessible to us.
>
>That is a great explanation. But in order to be a scientific explanation,
>it must have a way of being tested (and the fact that they were preserved
>nowhere at all cannot count!) The question then becomes how did they get
>from where they were to everywhere in the world at once without leaving a
>fossil trail?
>
>>Perhaps the
>>earlier conditions were not conducive to preserving fossils, despite the
>>similarity of the two groups of sediments. Perhaps the organisms that
were
>>ancestral were even more delicate and couldn't stand even these very
gentle
>>fossilization conditions.
>
>How then did they survive the rigors of the Precambrian world? We are
>talking here about the relatives of every modern Phylum. How could they
>all be that delicate until the beginnings of the Cambrian, then all
>suddenly become preservable?
>
>>One can ignore these alternatives, but that does
>>not mean they are not viable.
>
>You are a very creative individual, Kevin. That is a trait I admire. I
>think, though, in this particular case your creative energy is not well
>spent. Have a good day.
>
I love you too, Art. Still, I would rather take the risk of looking
ridiculous by speculating about possible naturalistic explanations, than to
refuse to do so simply because such explanations would challenge my personal
beliefs.
Kevin L. O'Brien