From: bobb@tekig1.PEN.TEK.COM (Bob Bales)
Newsgroups: talk.origins
Subject: Re: Why evolution is a BETTER theory (for Bob Bales)
Date: 6 Apr 92 19:46:23 GMT


Matt Brinkman writes:

>> me

>My name is Matt Brinkman, and I was a lurker during most of your last visit
>to talk.origins.  I started posting just before you took your extended
>vacation, and addressed myself minimally to anything you wrote, because I
>didn't want to horn in right in the middle of protracted discussions.

My point of view is that you shouldn't let that stop you.

>Ooops, almost forgot, there was the problem of Antarctic ice-core data that
>you were going to address before you left.  You could consider that an open
>question which Trygve Lode did not address.

Some of the responses I prepared while "away" dealt with the age question in
general.  I'll post them after I've explored the current topics a little more.


Matt outlines his basic position as follows:

>>[*] It is often said that if evolution *predicts* something which creation
>>merely *allows*, then evolution is a better theory.  Even leaving aside the
>>failed predictions of evolution (which I discuss in this posting and
>>elsewhere), the question is: better in what sense?  

>Better in a scientific sense, and better in the sense of more likely to be
>be THE correct theory, as I will demonstrate below.

-- some deletions --

>>And a theory which predicts something is not necessarily more likely to have
>>happened than one which is merely consistent with it.

>I disagree with this statement, because it is false.

I've deleted some of Matt's introductory material.  I hope not too much!

>Statement of the Problem:

>We have two theories x and y that we desire to judge the correctness of.  As
>Bob has so graciously pointed out, to claim that theory x is more correct
>than theory y, we need to show that theory x is more probable (i.e., has a
>greater likelihood of occurance) than theory y.

> Let us start by assuming that either theory x or theory y must be true.  In
>this case the probability that one of the two theories is correct is 1.  Now
> one can set up separate probability distributions for theory x and theory 
>y.  An experimentalist now measures a result z, which is consistent with both
>theory x and theory y.

>Handwaving Methodology:

>Assume that both theory x and theory y are correct.  This means that both
>have a probability distribution with an area of 1 (i.e., true).  Let us now
>distinguish our theories by noting that theory x only predicts the result
>z, while theory y predicts results a or b or c or z with equal likelihood.

Notice the specification of "equal liklihood."  With the adoption of a
probability distribution (which would not have to be equal likelihood),
theory y has gone from being a theory which is consisten with thw measured
result to a theory which predicts a different probablity for the result than
does theory x.

>This means that the area of the probability distribution of theory x for the
>result z is four times that of the area of the probability distribution of
>theory y for the same result.  This means that theory x is, on average, four
>times more likely to be the correct theory.  In general, the likelihood of
>a theory being correct is inversely proportional to the number of distinct
>results possible for a given measurement (i.e., inversely proportional to
the non-specificity of the prediction).

Almost, but not quite. The likelihood of a theory being correct is directly
proportional to the probability that, under the theory, the results would have
been as measured and inversely proportional to the probability that different
results would have been measured.

The reason that Matt can draw the above conclusion in this case is the uniform
probability distribution.  Under these condxitions, the probability of any
one result decreses in proportion to the number of results.  It is the
probability that is important, not the number of results.  In this case, the
distinction may seem to be splitting hairs, but it will become important later.


>Now let us assume that theory x now predicts result z for a given type of 
>measurement, result r for a second type of measurement, and so on and so
>forth, up to result n for a nth distinct type of measurement.  Theory y, on
>the other hand predicts the same results as theory x, but does not preclude
>the possibility of three other results (once again with equal likelihood)
>for each of the distinct types of measurments.  Using the same probabilistic
>argment as above, it is apparent that theory x is (4^n - 1) times more likely
>to be  correct than theory y, provided that all of the predictions of theory
>x reflect what is actually measured.

The important point about the argument is that it is *probabilistic.*  In other
words, even though theory y would allow the measured results in each case, it
is *statistically unlikely* that a *random choice* among the outcomes allowed
by the theory would agree with the measured resuilts every time.

>Now that I have managed to confuse everyone thoroughly, let me provide an
>example.

>Example:

>I have a waggish friend, Bill, who really hates washing dishes, but loves 
>watching television.  To decide who will do the dishes each night, we flip a
>coin with Bill always choosing heads and sticking me with tails.  Now, I have
>a sneaky suspicion that Bill is cheating by using a two-headed coin, but we
>have been friends for a long time and I would hate to lose that by falsely
>accusing Bill of cheating or by implying that he is cheating (e.g., look at
>the coin).

>Okay, the two theories are 1) The coin is fair and 2) The coin has two 
>heads.  Theory #1 predicts that the probability (i.e., the likelihood of
>occurance) of Bob winning for n consecutive nights is 2^(-n).  Theory #2 
>predicts that the chance of Bill winning for n consecutive nights is 1.  

Here, the theories make *different* predictions, so we can indeed judge them
on how results agree with predictions. The original situation I discussed
involved a theory which predicted results and another which is consistent with
them.  But. . . .

>It is clear that the likelihood that Bill is cheating increases exponentially
>as the number of his consecutive wins increases, and that only an extremely
>silly person would continue to believe the coin is fair while Bill racks up
>win after win after win.

It is theoretically possible, of course, for a fair coin to give a string of
heads of any length.  But Matt's analysis is correct: after a time, the "fair
coin" theory becomes silly.  Why is this?  Because as time goes on, the "fair
coin" theory becomes *less and less* consistent with results.  We discard the
theory when we judge it to *be inconsistent* and we do so because it *is*
inconsistent. This is a departure from the premise that we had a consistent
theory.

>Discussion:

>In this example, it is clear that theory #2 (i.e., a double-headed coin)
>makes a much more specific prediction on the outcome of n independent flips
>of a coin than theory #1 (i.e., a fair coin) does, with respect to consecutive
>heads. 

It is true that theory #1 does not predict the outcome of each flip.  But
theory 2 does predict specifically the probability that there will be a given
number of heads in a row.

>As the number of consecutive heads becomes larger, the greater specificity of
>theory #2 causes it to be exponentially more likely than theory #1.

But it is the predictions of theory #1 that allows us to make this judgement.
Imagine, for the moment, that the "fair coin" theory said, that while it is
possible to get a mixture of heads and tails using a fair coin, the probability
of obtaining a given number of heads in a row is unknown.

Then, when we were given a string of, for example, 20 heads, we could say, "The
probability of getting this result under theory #2 is 1, but the probability of
getting this result under theory #1 is ???"  We could not say which theory
would be more likely.  (We could say that theory #1 is no more likely than
theory #2, but not that it is less likely).

The ability to choose a theory derives from the ability to *compute* the
probabilities involved.

>It is clear that a theory that is merely consistent with experimental
>observations is much less likely to be correct than a theory that makes 
>specific accurate predictions about the experimental observations.

What Matt calla "a theory that is merely consistent with experimental
observations" is, in this example, a theory which predicts that a certain
outcome has a low probability.  It is only the circumstance that the number
of outcomes translates directly into probability that allows the above
statement.  In the general case, it is the probability that is important.

What the example shows is that, given a measured result, a theory that says
the result has a low probability is much less likely to be true than one which
says the result has a high probability.

>This is exactly the "likelihood of occurance" that Bob Bales is talking about
>above.

>To place this within the framework of Bob's original claim, as the theory 
>of evolution accurately predicts more and more available experimental results,

The theory of evolution does not accurately predict more and more results.
For example, in my discussion of _Archaeopteryx_, I mentioned that
evolutionists say that feathers evolved from scales.  I also pointed out the
evidence that indicates that did not happen.  And in discussing both this case
and the supposed transitions from reptiles to mammels, I pointed out that the
evolutionary theory requires intermediates which we have no reason to believe
existed/could exist.  (I probably didn't see all the responses to me, but
though I saw a number which said  I was wrong, I didn't see any which refuted
my position on these examples.)

These are just a few examples of the trend that, whether we look at current
organisms, past organisms, or biological processes, evolution raises more
unknowns and improbabilities than it makes accurate predictions.

>the likelihood that the theory of scientific creationism (which is merely
>consistent with those results) is the correct theory becomes vanishingly
>small.

Not so.  Let me emphesize that I agree with Matt's analysis as applied to his
exaple. In that Matt's example, he derived a formula for the probability
that a given number of successive heads would occur with a fair coin, and then
dicarded the fair-coin theory when that probability became vanishingly small.
In the case of creation, Matt has not even defined in a  clear way the
probability that the obseved results are due, respectively, to evolution and
to creation.  One undefined probability cannot be compared to another and
cannot be called vanishingly small.  Since he has not computed the probability
of creation, Matt does not have a situation is which his argument can be
applied.

Although he hasn't computed the probability of creation, judging from what he
has said, and also extrapolating from common evolutionary arguments, he seems
to me to be saying the following:

1. Evolution would, with high probability, have produced something like we see.

2. There would be many possibilities for creation besides what we see.

3. If organisms had been created, out of all the possibilities in 2, for
   the Creator to have chosen the ones we see would be unlikely.

For a specific example, I'll use the conclusion that mankind and apes are
related, based on DNA (and other) similarities, and discuss why each of these
statements is not justified, based on what we see.

1. To begin with, it is theorized that what is evolved depends on what
   variations occur and what the selection pressures are.  The results are not
   preordained.  Evolution could producle multiple possibilities.  Thus, it is
   subject to the same argument Matt uses against creation.

   Consider what is necessary for man and apes to have evolved from a common
   ancestor:

   A. The common ancestor would have had to exist.

   B. The gentic material of the common ancestor would have had to be capable
      of variation in the direction of apes.

   C. There would have had to be selection pressure in the direction of apes.

   D. The gentic material of the common ancestor would have had to be capable
      of variation in the direction of man.

   E. There would have had to be selection pressure in the direction of man.

   This is heavily biased in favor of evolution, since there should be many
   more steps. B, C, D, and E should be repeated for each of the intermediates
   needed along the path.

   We do not see direct evidence for any of these.  What probability should we
   assign?  If we use a generous 0.9, we get 59%.  If we reason that, with
   no better information, we should use an 0.5 probability for each item, we
   get an overall probability of only about 3%.

2. The question is: if we start wiith the assumption that apes have the DNA
   which they do, how many possibilities for the DNA of man could the creator
   have chosen?  It's obvious that not just any DNA would produce a man (or a
   woman).  As of now, the only way of showing that a particular set of DNA
   will "work" for humans is to observe a human having that DNA.  And exactly
   *one* set passes the test.  To say that there are other possibilities from
   which a Creator could have chosen is nothing but speculation.

3. This appears to be the key of all Matt's assumptions.  He translates the
   number of selections directly into the probability of the selection,
   apparently made on a random basis.  However, if we assume that the
   Creator of living organisms would show the traits of the creators of other
   objects, we have the following observation.  *Creation is not a ramdom act.
   Creators do not make random choices.*  Matt is attempting to reject
   creation based on an assumption about creation which is *known* to be
   wrong.

>On the other hand, as I pointed out in my example above, at some point anyone
>with even the eensiest portion of rational intelligence will quickly be
>forced to conclude that the merely consistent creationism theory is almost
>certainly false.

The stated reason that creation is to be rejected is that it would be expected
to give results other than what we see.  As I pointed out just above, there is
no evidence that creation would be expected to give other results.  And the
rational person can be expected to look at the evidence.  Such looking would
quickly show that there is no reason to conclude creationism is even probably,
let alone almost certainly, false.

Furthermore, Matt agrees that creationism is consistent with the evidence.
When this is compared with evolution, which is inconsistent with the evidence,
the conclusion is that creation is more likely to be true.

   Bob Bales
   Tektronix, Inc.

I help Tektronix make their instruments. They don't help me make my opinions.