[asa] homology and analogy

Doug:

Thank you for your patience, but I still don't think we are quite
communicating.

I will try to give an example of what I am after.
Keep in mind this is only an example.

1) Trait A is common for species class C.
2) Trait A is a contingent characteristic of species class C.
3) Contingent traits like A are possessed only by entities that
   share a common origin.
4) Hence, species class C share a common origin.

I believe this to be logically sound.

We would want to hedge on some of the assertions to make it probabilistic.
But the main point to observe in the presentation is that premise #3
is required to restrict the possibilities of the world.

To make it sound more probabilistic we might change this to

1) Trait A is common for species class C.
2) Trait A is a contingent characteristic of species class C.
3) Contingent traits like A are most likely possessed only by entities that
   share a common origin.
4) Hence, species class C most likely share a common origin.

So far I hope we are in agreement.
My principal point is that the argument to this point does not differentiate
between any brand of evolution, ID, or perhaps a hundred other possibilities.

You want to argue, as I understand it, that relative to all other alternatives
that what you call "evolution" is the most probable account.

That is crudely speaking:

5) Commonality of species is either "evolutionary" or Designed.
6) If "evolutionary", species class C share commonality common descent.
7) If Designed, species class C share commonality of Designer.
8) If evidence E, then common descent more likely than Designer.
9) E is true.
10) Therefore, commonality more likely common descent.

Three points about this model argument.

1) I don't know what you mean by "evolutionary." I have intentionally left
it open, merely using your wording as a place holder for whatever you mean by
it. I have presented the argument as if there are only two alternatives.
Logically, of course, the number is large, larger than we can imagine.
We might think pseudo-logically as considering the two possibilities as
modally the only "live" alternatives. But other alternatives could
be considered, even versions of "evolution" that are contrary to your
version.

2) You suggest that the argument is stronger than I have offered here.
You say,
"Evolution ... can now be regarded as "fact" because it is the ONLY mechanism
that is completely specified by the complexity of information that is known
about biology (emphasis added)."
Such confidence entails that evidence E is a strong defeater of every other
"live" possibility. We won't worry for the time being of all the other
possible alternatives.

3) It is in the explicit description of E that the tautology may make its
showing. I'm certain that E cannot be easily stated. But if you could
make a stab at offering one principal feature of E, it would be helpful.
I know Darwin thought that homology alone was enough to argue for his
version of evolution. But I believe his argument was tautologous.

Since the argument is probabilistic, we must be able to say something about
the probability space. That means that any evidence E cannot be viewed
in isolation. E is only meaningful within a described world or a world of
possibilities. The rest of the "world" must be laid upon the table.

BTW, my intention is not here to argue against evolution, however construed,
but rather to lay bare our thinking.

Thanks,

bill

On Sat, 10 Oct 2009 19:58:50 -0500, Douglas Hayworth
<becomingcreation@gmail.com> wrote:
> On Fri, Oct 9, 2009 at 10:51 PM, wjp <wjp@swcp.com> wrote:
>
>>
>> Perhaps both you and Doug are correct.
>>
>> But, as far as I can tell, you have provided no reasons for me to see
> why.
>>
>> If you follow my argument, you ought to see that TE is one of those
>> alternatives
>> that are contrary to the Darwinian position I have outlined.
>>
>> The argument for common descent appears probabilistic, but it still
> seems
>> to
>> me that there is no logical way to eliminate from the argument for
>> homologous structures other possibilities than Darwinian evolution,
>> including
>> TE and ID.
>>
>> If you see the logical argument differently, you will have to outline
> the
>> argument, and demonstrate that it is not a tautology.
>>
>
> Of course, anything is possible (designed appearance of age and designed
> appearance of phylogenetic relationship), but do you really want to hold
> out
> for those unlikely possibilities when a completely sufficient and
> demonstrably scientifically fruitful alternative mechanism is available?
>
> The nested hierarchy of homology is not a tautology. The Linnaean
> taxonomic
> system is a recognition of this nested structure, and it predates notions
> of
> descent with modification and multiplication of species (i.e., evolution).
> Together, the known mechanisms of heredity and the genotype-phenotype
> relationship are exactly the sort of system that will produce this pattern
> of variation. Evolution, which in its genetic basis was only a
> "hypothesis"
> for Darwin, can now be regarded as "fact" because it is the only mechanism
> that is completely specified by the complexity of information that is
> known
> about biology.
>
> Doug

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Received on Sun Oct 11 00:19:08 2009