Re: Revised Tautology FAQ - Thread-2

On Aug 18, 9:46 am, j...@xxxxxxxxxxxxx (John S. Wilkins) wrote:
We need to distinguish several things that get called tautologies:

1. Definitional tautologies; bachelors are unmarried males.

From: "Is Natural Selection a tautology"

http://groups.google.com/group/talk.origins/browse_frm/thread/e43bdc0e345b31d4/4fe10dbc2ed2789e?lnk=st&q=#4fe10dbc2ed2789e


{{{
<pre>
There are two different usages of the word "tautology". One is
classical and refers to redundancies in expressions, e.g., "an
unmarried bachelor". The "unmarried" is redundant because a bachelor
is unmarried by definition. The other usage is much more modern and
apparently is due to Wittgenstein. It refers to propositions that are
true by virtue of their logical form irrespective of the truth or
falsity of the variables contained within the proposition. Thus,
according to this usage, "A or ~A" is a tautology.


The difficulty (and it is a real one) is that the principle of natural
selection can be formulated both in tautological and non-tautological
forms depending on how fitness is defined. The error of logic is to
define natural selection tautologically and then argue for its
empirical content.

Richard Harter, c...@xxxxxxxx
http://www.tiac.net/users/cri
</pre>
}}}


=== post 17 ===
Richard Harter:

"Natural selection" is not a self contained expression; it is a label
for a description of a process. When you unpack the description you
run into a difficulty with the concept of fitness. If you define
fitness as reproductive fitness (as measured by actual reproductive
success) then the definition of natural selection is circular. If you
define fitness in terms traits which "ought" to be superior then it is
not circular.




The fact that creationists like to raise this red herring simply indicates
their lack of relevant arguments.

That is as it may be. It remains that the formulating the principle
of natural selection in a non-tautological form is a task with serious
difficulties.

=== post 18 ===
[[HersheyhPragmatics]]

Howard misquoted him:
"Natural selection" is not a self contained expression; it is a label
for a description of a process. When you unpack the description you
run into a difficulty with the concept of fitness. If you define
fitness as reproductive fitness (as measured by actual reproductive
success) then the definition of natural selection is circular.


'''WHAT MATTERS TO THE CONCEPT OF NATURAL SELECTION''':

The success of one group relative to another group with a different
phenotype does matter to the concept of natural selection.

''Fitness = measured reproductive success of a group is a tautology in
the same way that every definition is a tautology.''

==== post18 cont NS IS DEFINED ====
Howrard defined NS:

And if you have a comparison that shows no difference
in fitness of the two groups you examine (that is fitness
(reproductive success) of group A/fitness B =1), you won't have
natural selection occurring there either.

For natural selection you need fitness A/fitness B to be significantly
different from 1. In
fact, that is not a bad definition of natural selection if you want a
nice short one:

natural selection is defined as and occurs when the measured
reproductive success of intraspecies variants with phenotype
A/ measured reproductive success of variants with phenotype B in the
same environment is significantly different from 1. Which phenotype
is fitter is determined by the direction of the difference. Of
course, as all good definitions should be, mine is a tautology, as
indicated by the = sign.


==== When does Natural selection occur ====
I agree that the term 'fitness' is used for the directly measureable
quantity 'reproductive success'. But I have no problem with that
being a tautology, since it is a definition of a specific calculated
quantity. But absolute 'reproductive success' or 'fitness', _per se_,
tells us nothing about whether natural selection is occurring. Only
*differential* reproductive success does.


==== What is 'fitness' used for ? ====
I agree that the term 'fitness' is used for the directly measurable
quantity 'reproductive success'. But I have no problem with that.


==== How is reproductive success measured ? ====
??


==== What is absolute fitness ? ====


=== Post 19 Harter ===


==== Fitness is comparative ====
Er, Howard, nobody was talking about "absolute fitness" except you.
'''It is understood that fitness is comparative.''' The question at
hand is whether natural selection '''defined''' in terms of measured
relative reproductive success is tautological. You seem to agree.

==== What is Absolute Reproductive Success ? ====
Now here I have no notion of what you mean by "absolute reproductive
success". What on Earth are you talking about.


==== Claim of Darwinian theory ====
The issue at hand is that natural selection as propounded by Darwin
and as regularly treated in evolutionary theory selects for
adaptation, fitness on a priori grounds of superior functionality.
This is a major claim of Darwinian theory.

The difficulty here is with arguing on one hand that "fitness" is
synonymous with whatever happens and on the other that "fitness" is
adaptive.


=== Notes ===

==== Claim of Darwinian theory ====

'''Richard''':
Darwinian theory really is about the natural selection of traits in
populations by virtue of
the superior fitness of the traits.

''' Harter ''':
The issue at hand is that natural selection as propounded by Darwin
and as regularly treated in evolutionary theory selects for
adaptation, fitness on a priori grounds of superior functionality.
This is a major claim of Darwinian theory.
The difficulty here is with arguing on one hand that "fitness" is
synonymous with whatever happens and on the other that "fitness" is
adaptive.



=== Post 20 Howard ===


==== Fitness that is relevant to natural selection ====
The fitness that is relevant to natural selection, however, is
'relative fitness', where
the fitness of a subgroup is compared to either that of a
phenotypically different subgroup or to the mean population fitness
(usually by dividing the subgroup fitness by mean population fitness
and normalizing all values to the case with highest 'relative
fitness'). If there is no significant difference in relative
fitnesses, there is no selection going on that can distinguish between
these phenotypes


==== When does natural selection not happen ====
What that means is that natural selection is *not* going on when there
is no significant *difference* in measured fitness.



==== Relationship between phenotype and reproductive success - RS
====
Of course, one still has the responsibility to present an argument
that the correlational
relationship between phenotype and differential reproductive success
is causal rather than casual; that the specified phenotype is the
reason for the differential reproductive success.


==== Fitness is measured as whatever happens ====
"Fitness", _per se_, is indeed measured as whatever happens (that is,
one measures reproductive success empirically). But it is 'relative
fitness' and not the directly measured 'fitness' that produces the
significant correlation between different phenotypes and greater
reproductive success that is required to make the claim that natural
selection has occurred. Further evidence, of course, is required to
demonstrate what it is about thsee correlations that is causal.
'Adaptive' is *defined* as those phenotypic features that result in
the most (reproductively) success in a particular environment. I
certainly
think it would make little sense to call such features "maladaptive",
as that would run counter to most people's notions of what "success"
or "beneficial" mean when you look at life. One can always argue that
the 'goal' of life ought not to be maximal reproductive success, but
that is a religious argument that doesn't seem to apply to, say,
insects, but is
*certainly* one that humans can and do consider for themselves.


=== Post 20 Richard Wein ===

==== "natural selection" *is* an expression. ====
In this sense, "natural selection" *is* an expression.


==== Is the term NS tautological or the definition of it ? ====
Perhaps what you're getting at is that I only considered whether the
term
"natural selection" is tautological, and not whether the *definition*
of
that term is tautological. That would be a good point, and I'll deal
with it
below. First we need a definition of "natural selection".


==== Definition of natural selection by Richard Wein ====


==== What is the best definition of natural selection ? ====
* >When you unpack the description you
* >run into a difficulty with the concept of fitness.

So, I guess you're defining "natural selection" as "survival of the
fittest". I'm not sure this is the best definition, but let's go with
it.


==== Tautological expressions and propositions ====
* >There are two different usages of the word "tautology". One is
* >classical and refers to redundancies in expressions, e.g., "an
* >unmarried bachelor". The "unmarried" is redundant because a
bachelor
* >is unmarried by definition. The other usage is much more modern
and
* >apparently is due to Wittgenstein. It refers to propositions that
are
* >true by virtue of their logical form irrespective of the truth or
* >falsity of the variables contained within the proposition. Thus,
* >according to this usage, "A or ~A" is a tautology.

This is the same distinction that I made, between a tautological
*expression* and a tautological *proposition* (or assertion), e.g.
between
"an unmarried bachelor" and "all bachelors are unmarried".

The tautological *expression* ("an unmarried bachelor") contains a
redundant word ("unmarried"), but has meaning and can be used to form
a
meaningful proposition, e.g. "John is an unmarried bachelor". This
proposition is *not* a tautology--it gives us real information about
John,
albeit in an unnecessarily verbose manner.

The tautological *proposition* ("all bachelors are unmarried"), on the
other
hand, gives us no information that is not already contained in the
definition of the word "bachelor".

Similarly, "survival of the fittest" may well be a tautological
expression,
but this does not deprive it of meaning.

The difficulty (and it is a real one) is that the principle of natural
selection can be formulated both in tautological and non-tautological
forms depending on how fitness is defined. The error of logic is to
define natural selection tautologically and then argue for its
empirical content.

I assume that, by "empirical content", you mean empirical support for
a
proposition. You cannot have empirical support for an expression or
definition, and the empirical data are not necessarily *contained* in
the
proposition.

So what proposition are you referring to here? Presumably you're
referring
to the proposition that natural selection occurs. But this proposition
is
not, in itself, an interesting or controversial one, so it's not
important
whether it's tautological or not.

The interesting proposition is that natural selection plays a
significant
role in evolution. And this proposition is non-tautological even if
the
expression "natural selection" is tautologous. Unpacking the
proposition, we
get: "the tendency to reproductive success of those with the greatest
inherited propensity for reproductive success plays a significant role
in
evolution". The first 10 words of this proposition are redundant, as
we
could just as well write: "inherited propensity for reproductive
success
plays a significant role in evolution". But the fact that part of the
proposition is redundant does not make the proposition itself a
tautology.

Thus, the issue of tautology of "natural selection" only arises in the
context of:
* (a) the possible tautology of a proposition which is of no
interest; or
* (b) the possible tautology of an expression, and I've shown that
tautology
in an expression does not deprive it of meaning.

I therefore stand by my assertion that arguments about the possible
tautological nature of "natural selection" are nothing but a red
herring




=== Post 22 richard harter ===

==== Fitness of individuals and fitness of traits must not be confused
====

==== What difference between fitness of individuals, traits and
intrinsic fitness ? ====
I appreciate your qualms. May I point out that it is easy to confuse
fitness of individuals and fitness of traits. Darwinian theory really
is about the natural selection of traits in populations by virtue of
the superior fitness of the traits.

==== "inherited propensity for reproductive success" ====
(See other followup.) The difficulty with "inherited propensity for
reproductive success" is with establishing that there is such a thing
in any meaningful sense. Suppose, to be slightly more specific, you
have a species with two alleles A and a of a gene. At one particular
time you measure the prevalence of the two alleles and discover that
the populations are dominated by allele A and that, in the current
generation, those with allele A (prokaryotes for convenience) have a
better track record at reproducing. Does this tell you that allele A
has superior fitness? Alas, no. At a later time you may make the
same measurement and discover that allele a now appears to be
superior. How do you determine these propensities?


==== adaptation is a consequence of natural selection ====
* >So what proposition are you referring to here? Presumably you're
referring
* >to the proposition that natural selection occurs. But this
proposition is
* >not, in itself, an interesting or controversial one, so it's not
important
* >whether it's tautological or not.

No. I'm referring to the thesis that adaptation is a consequence of
natural selection. This is fundamental to evolutionary theory. It is
generally agreed (except possibly by Moran) that genetic drift does
not explain adaptation. You cannot defend this



==== Genetic drift explains adaptation says Moran others disagree ====
No. I'm referring to the thesis that adaptation is a consequence of
natural selection. This is fundamental to evolutionary theory. It is
generally agreed (except possibly by Moran) that genetic drift does
not explain adaptation. You cannot defend this thesis if you are
using a circular definition of natural selection.



=== post 23 ===

==== natural selection is some people having more kids than others
====
So, if some people are defining "natural selection" as merely the fact
that
some individuals have more offspring than others, without mentioning
that
the differential reproductive success is partly based on inheritance,
then I
think this is unfortunate, but not necessarily serious, as long as the
full
description of the theory of evolution mentions inheritance. In any
case,
this limited definition is not circular.



=== post 24 Hershey Howard ===
==== natural selection not synonymous with evolution ====

Although natural selection certainly plays a major evolutionary role,
it is not synonymous with evolution. You can
have natural selection without evolutionary impact and you can have
evolution (of the neutral kind) without natural selection. If that is
what you mean by "intrinsic fitness", I agree, but would prefer that
it be called the "heritable component of fitness". The "heritable
component of fitness" is important for evolution.


==== The idea of intrinsic fitness ====
OTOH, if by 'intrinsic fitness' you mean the idea that a phenotype has
an 'intrinsic' fitness value in the sense that that value or
directionality will adhere to the phenotype in any other environment,
I would disagree most strongly.

==== How is fitness determined ? ====
The concept described above as being 'intrinsic fitness' is precisely
the type of idea with which I disagree strongly. Fitness is
determined by the interaction of phenotype and environment.
It is not an intrinsic property of phenotype alone.


==== Howard disagrees with Richard Wein over the concept of fitness
====
* > It isn't possible to measure intrinsic fitness precisely.
Observed fitness
* > is only a statistical approximation to intrinsic fitness. But
that's no
* > reason why we can't define a concept of intrinsic fitness.

The concept described above as being 'intrinsic fitness' is precisely
the type of idea with which I disagree strongly. Fitness is
determined by the interaction of phenotype and environment. It is not
an intrinsic property of phenotype alone.

TAGS: [[RichardWein]] , [[RichardHarter]] , HersheyhPragmatics


==== Where does Natural Selection occur ? ====
I think the theory of evolution is clear on this point. Organisms have a
propensity for reproductive success which includes a hereditary element. Or,
to put it another way, fitness is partly inherited.

Fitness is *often* partly inherited because phenotypes are *often*
partly a consequence of genotypes. Selection, however, is independent
of whether or not the phenotype is or is not a consequence of
genotype. But evolutionarily relevant fitness most certainly is not
independent of whether the phenotype is or is not a consequence of
genotype. Selection occurs at the phenotypic level and that is where
fitness is determined as well. The environment does not 'read'
genotypes; it does 'read' phenotypes.


==== Where is fitness determined ? ====
Fitness is *often* partly inherited because phenotypes are *often*
partly a consequence of genotypes. Selection, however, is independent
of whether or not the phenotype is or is not a consequence of
genotype. But evolutionarily relevant fitness most certainly is not
independent of whether the phenotype is or is not a consequence of
genotype. Selection occurs at the phenotypic level and that is where
fitness is determined as well. The environment does not 'read'
genotypes; it does 'read' phenotypes.


==== Genotypic variation created by natural selection ====
One way to generate phenotypic variation is via genotypic
variation (this is the only evolutionary relevant type of phenotypic
variation). The only way known by which genotypic variation is
generated in nature is through random mutation. That, of course, is
how natural selection is connected to evolutionary change over time.
But it does not mean that "natural selection" requires "random
mutation" to be included in its definition.


==== Natural selection can have both an evolutionary and non-
evolutionary consequence ====
I described what "natural selection" is. The term is not simply a
synonym for "evolution". One can have natural selection that has no
evolutionary consequences. One can also certainly have natural
selection that does have evolutionary consequences. Whether the
phenotypes have a genetic basis is what determines this. You can also
have evolutionary consequences in the absence of natural selection
(neutral drift, founder effects, etc.). Natural selection is a
mechanism that is not identical to evolution. It is one mechanism by
which evolutionary change can occur.


==== Do all phenotypes have a genetic basis ? ====
I described what "natural selection" is. The term is not simply a
synonym for "evolution". One can have natural selection that has no
evolutionary consequences. One can also certainly have natural
selection that does have evolutionary consequences. Whether the
phenotypes have a genetic basis is what determines this. You can also
have evolutionary consequences in the absence of natural selection
(neutral drift, founder effects, etc.). Natural selection is a
mechanism that is not identical to evolution. It is one mechanism by
which evolutionary change can occur.


=== post 25 Richard ===
==== Functional fitness fundamental element in Darwin's argument ====
Presumed functional fitness of traits (with heritability and
variation) is a fundamental element in Darwin's argument.


==== NetcomJump ====
[[NetcomJump]] , [[RichardHarter]]
Richard Wein wrote

"Natural selection" cannot contain circular reasoning because it's an
*expression*, not a *proposition*.
The proposition "natural selection occurs" may contain circular reasoning
(depending on how you define natural selection) but it's a straw man.

No, this is hopelessly confused. The term 'straw man' is applied to
*arguments* : "Natural selection occurs" is not an argument.
Futhermore 'circular reasoning ' occurs in an argument when
one of the premises is identical to the conclusion - but again
""Natural selection occurs" is not an argument.



=== Post 41 ===

==== Pattern design distinction ====
See [[RichardHarter]]
Is there any explanation for HOW "natural selection"
causes adaptive evolution, or does it just happen "by
definition"?

I will repeat part of a reply to a post that I tried to e-mail to you,
but got returned.

Perhaps an analogy is in order. The environment's role in the
selection process is like that of a seive in the sorting process of
mixed gravel and sand (a mixture of size phenotypes, if you will). A
seive blindly sorts the mixture and you wind up with larger gravels
being largely retained and smaller gravels being largely lost by
passing through. Notice that there is a directionality to this
sorting process. It is the *larger* gravels that are retained by the
seive. To claim that it is the *smaller* gravels that get retained by
the seive would be to distort the common meaning of "larger" and
"smaller" so that they mean the opposite of what most people
understand. In the same way, the environment retains those organisms
best adapted to that sorting environment. Natural selection can no
more selectively retain the phenotypes maladapted to its environment
than a seive can selectively retain the smaller gravels. To retain
maladapted organisms, you have to have an intelligent designer
intervene to save them (as humans sometimes do in artificial
breeding). Retention of well-adapted organisms is not evidence for
intelligent design; selective retention of maladapted organisms is.



.

Relevant Pages

  • Re: Revised Tautology FAQ - Thread-2
    ... trait does or does not contribute to an organism's fitness. ... natural selection is testable and not a tautology. ... Creationists like Henry Morris and Ann Coulter argue that SoF and NS ...
    (talk.origins)
  • Re: Revised Tautology FAQ
    ... A tautology is saying the same thing over twice, ... When people say that natural selection is a tautology, ... Fitness will increase in successive generation. ... of a trait that survives in the next generation. ...
    (talk.origins)
  • Re: Harshman says successful reproduction is natural selection
    ... At a guess it's that natural selection can't operate if there ... is no actual entity of "fitness" on which to select. ... Hutton's tautology reduces to: ... the bulk of the official Wikipedia article here ...
    (talk.origins)
  • Re: Removing Lewontins Fallacy From Hamiltons Rule
    ... >>> required to break Hamilton's fitness tautology. ... verified or refuted within nature. ... gene centric argument that "genes use organisms to replicate genes" which is ... >> Also, natural selection does not care about causation, only ...
    (sci.bio.evolution)
  • Re: The uncorrected simplifications/oversimplifications of Hamiltons Rule (Re: Removing Lewontins Fa
    ... > There are no axiomatic truths within the sciences only within mathematics. ... > altruism (organism fitness altruism) within nature as supposedly, ... > Hamilton's tautology for the diploid case. ...
    (sci.bio.evolution)
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