| Topic: |
Religions > Atheism |
| User: |
"david ford" |
| Date: |
27 Apr 2004 11:13:51 PM |
| Object: |
"A Good Tautology is Hard to Avoid" |
I don't particularly care about the tautology objection to the theory
of natural selection. However, the essay below deals with a T.O. FAQ
and might be of interest.
Eric Anderson, "A Good Tautology is Hard to Avoid"
http://www.evolutiondebate.info/A%20Good%20Tautology%20is%20Hard%20to%20Avoid.htm
Critics of evolutionary theory have long argued that the concept of
natural selection is a tautology. John Wilkins seeks to counter this
argument in his article "A Good Tautology is Hard to Find" on the
site, The Talk.Origins Archive.
Wilkins' discussion, found at
http://www.talkorigins.org/faqs/evolphil/tautology.html, contains two
points that I would like to address. The first is Wilkins' contention
that the concept of natural selection is not a tautology. The second
is his contention that natural selection rules out many possibilities,
which adds to its substantive explanatory power. Let's examine each
of these points in turn.
Tautology
In his article, Wilkins states:
"The simple version of the so-called 'tautology argument' is this:
Natural selection is the survival of the fittest. The fittest are
those that survive. Therefore, evolution by natural selection is a
tautology (a circular definition).
The real significance of this argument is not the argument itself, but
that it was taken seriously by any professional philosophers at all.
'Fitness' to Darwin meant not those that survive, but those that could
be expected to survive because of their adaptations and functional
efficiency, when compared to others in the population."
In other words, according to Wilkins, Darwin used fitness to mean not
those that did survive but those that were expected to survive. Thus
Wilkins implies that we will not have a tautology if we reword the
definition as follows: "Natural selection is survival of the fittest.
The fittest are those that are expected to survive." If natural
selection is properly doing its job of selecting, which we are assured
it always does, then those that are expected to survive will be those
that will survive. So if we take what would otherwise be a tautology
and change the verb tense, then it is no longer a tautology?
The problem is that under Wilkins' approach, natural selection will
mean nothing more than survival of those that are expected to survive,
and we are still left with a tautology. We haven't gotten anywhere by
shifting the focus from those that did survive to those that are
expected to survive. In fairness, there is a way out of the tautology
problem, as I will discuss below, but natural selection needs to be
formulated much more carefully than just proposing that we should
focus on expected survival rather than actual survival.
Wilkins' next sentence is as follows:
"This is not a tautology, or, if it is, then so is the Newtonian
equation F=ma (Sober 1984, chapter 2), which is the basis for a lot of
ordinary physical explanation."
This is tantamount to saying: "Even if natural selection is a
tautology, so what? It still explains lots of good stuff." Now I
doubt Wilkins really believes that F=ma is a tautology; rather he is
arguing that the logical construction of natural selection is
essentially analogous to other constructions that we accept as good,
valid scientific statements. Unfortunately, there is too much
reliance on Sober and too much reliance on a bad analogy.
Wilkins' confusion results from a failure to distinguish between two
very different logical constructions: equivalence and tautology.
Equivalence is a pure A=B construction. Under Wilkins' statement,
6=2*3 would also be a tautology. But it is not; it is a statement of
equivalence.
In contrast, a tautology is essentially a logical argument or
proposition of causation (or, if you prefer, premise and conclusion)
with two parts: (1) an if . . . then . . . relationship, such as If A,
then B, coupled with (2) a definition of A (the cause or the premise)
by reference to B (the effect or the conclusion). This is precisely
the problem that plagues natural selection as it is so often
described: If the organism is fit, then it will survive; and fitness
means that it did survive (or will survive, or is expected to survive,
take your pick).
Let's look again at the Newtonian equation F=ma. Even though force,
mass and acceleration can be mathematically described in terms of each
other, they do not cause each other. Force doesn't cause mass; mass
doesn't cause acceleration. The mathematical equation is an
equivalence statement of their relationship.
In contrast, natural selection posits a cause-effect relationship.
Because of an organism's fitness, it is theorized, the organism
survived (will survive, is expected to survive, etc.). Thus natural
selection is in the business of explaining what leads to or causes
survival. So far, so good. But when we then seek to explain this
causal relationship by defining the causative element ("fitness") in
terms of the resulting element ("survival"), we have a tautology.
I indicated that there is a way out of the tautology problem, and
there is. But only if the cause, fitness, is carefully defined by
reference to characteristics that are independent of the result,
survival. Thus, natural selection would not be a tautology if we
define fitness in terms of independent characteristics such as speed,
or bodily efficiency, or reproductive capability. If we define
fitness this way, then we can hypothesize that natural selection
actually means survival of the fleetest, or survival of the most
efficient, or survival of the most prolific.
Later in his article Wilkins alludes to such possible approaches to an
understanding of fitness. This is certainly a step in the right
direction, and if a careful definition of fitness is adopted we can
avoid the tautology fallacy. However, the recurring frustration
voiced by critics of evolutionary theory is that proposed definitions
are notoriously slippery, and it seems nearly impossible to pin
evolutionary theorists down on a working definition. And without a
concrete working definition of the causative element, what exactly is
it that we are supposed to test?
This is the kind of frustration with the concept of natural selection
voiced by many critics, and that brings us to Wilkins' second point.
Ruling Out
Wilkins states:
"However, there is another, more sophisticated version [of the
tautology argument], due mainly to Karl Popper (1976: sect. 37).
According to Popper, any situation where species exist is compatible
with Darwinian explanation, because if those species were not adapted,
they would not exist. That is, Popper says, we define adaptation as
that which is sufficient for existence in a given environment.
Therefore, since nothing is ruled out, the theory has no explanatory
power, for everything is ruled in.
This is not true, as a number of critics of Popper have observed since
(eg, Stamos (1996) (note 1)). Darwinian theory rules out quite a lot.
It rules out the existence of inefficient organisms when more
efficient organisms are about. It rules out change that is
theoretically impossible (according to the laws of genetics, ontogeny,
and molecular biology) to achieve in gradual and adaptive steps (see
Dawkins (1996)). It rules out new species being established without
ancestral species."
What Wilkins is saying in effect is that because genetics, ontogeny,
molecular biology, etc. are testable hypotheses, and because natural
selection is presumed not to violate them, then natural selection
rules out violations of those natural laws, which adds to its
explanatory power.
First of all, Popper was no doubt making a practical point about the
substantial challenge of pinning down a working definition of the
causative element, and thus the practical difficulty of natural
selection teaching us anything useful. No doubt Popper would agree
that violations of natural law are not available to natural selection.
Second, with apologies to Dawkins, whom Wilkins cites, I believe a
moment's reflection will tell us that natural selection does not rule
out violations of genetics; genetics does. It does not rule out
violations of molecular biology; molecular biology does.
To be sure, natural selection's inability to violate well-established
natural laws is a welcome admission, but Wilkins implies that this is
a property of natural selection itself. This is like saying that
archeology rules out violations of physics. No it doesn't; physics
does. Natural selection cannot set the parameters of genetics or
molecular biology or physics; it can only be bound by them.
Ultimately, Wilkins' statement is probably an example of attributing
much more explanatory power to natural selection than it really has.
True enough for natural laws you say, but what about the first "ruling
out" cited by Wilkins in the above quote: namely, that natural
selection "rules out the existence of inefficient organisms when more
efficient organisms are about?" Now we are getting somewhere. I
believe this "ruling out" is in fact a logically appropriate
statement. Now if only we could come up with a concrete definition of
efficiency, then we would have a definition of fitness that we could
apply and test.
Unfortunately, despite all the intervening decades since Darwin, we
still seem to be unable to come to any concrete working definition of
fitness. This is the source of the disillusionment with the concept
of natural selection expressed by so many.
Conclusion
The concept of natural selection as proposed by Darwin, and as often
applied today, is likely a tautology. The only way for us to keep it
from failing as a tautology is to carefully define fitness in terms of
characteristics that are independent of survivability. And once saved
from this logical precipice, the only way to give natural selection
any real explanatory substance is to come up with a concrete working
definition of fitness that can be tested. Although various vague
characteristics have been proposed, such as efficiency, it has been
notoriously difficult to pin down any useful working definition of
fitness over the past century and a half. Without such a definition,
we cannot carry out meaningful empirical test to determine the
correctness of the hypothesis.
Given the difficulties of defining fitness in a meaningful way, a word
play on the title of Wilkins' article might provide us with an
appropriate motto for evolutionary theory today: "A Good Tautology is
Hard to Avoid."
Eric Anderson
July 18, 2003
===========================================================
For Further Reading
Brady and Waddington on tautology
http://www.google.com/groups?selm=Pine.LNX.4.10A.B3.9910102327070.29158-100000%40jabba.gl.umbc.edu
Grene on Schindewolf; Margulis; Calder; Gould on hogwash in
evolutionary theory
http://www.google.com/groups?selm=Pine.SGI.3.95.970721233453.16211D-100000%40umbc9.umbc.edu
Rosen
http://www.google.com/groups?selm=Pine.SGI.3.96A.980913231459.8446A-100000%40umbc8.umbc.edu
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| User: "Editor of EvilBible.com" |
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| Title: Re: "A Good Tautology is Hard to Avoid" |
28 Apr 2004 11:14:02 AM |
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"david ford" <dford3@gl.umbc.edu> wrote in message
news:b1c67abe.0404272017.3fb911d4@posting.google.com...
I don't particularly care about the tautology objection to the theory
of natural selection. However, the essay below deals with a T.O. FAQ
and might be of interest.
Perhaps you don't care for the tautology objection to the theory of natural
selection because it is totally bogus. Why bother posting something you
know is incorrect?
.
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| User: "AC" |
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| Title: Re: "A Good Tautology is Hard to Avoid" |
28 Apr 2004 11:31:46 AM |
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On Wed, 28 Apr 2004 16:14:02 +0000 (UTC),
Editor of EvilBible.com <Dont_Reply@Here.com> wrote:
"david ford" <dford3@gl.umbc.edu> wrote in message
news:b1c67abe.0404272017.3fb911d4@posting.google.com...
I don't particularly care about the tautology objection to the theory
of natural selection. However, the essay below deals with a T.O. FAQ
and might be of interest.
Perhaps you don't care for the tautology objection to the theory of natural
selection because it is totally bogus. Why bother posting something you
know is incorrect?
Because that is was David does.
--
Aaron Clausen
mightymartianca@hotmail.com
.
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| User: "david ford" |
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| Title: Re: "A Good Tautology is Hard to Avoid" |
28 Apr 2004 10:43:53 PM |
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AC <mightymartianca@hotmail.com> wrote in message news:<slrnc8vnb2.3d0.mightymartianca@alder.alberni.net>...
On Wed, 28 Apr 2004 16:14:02 +0000 (UTC),
Editor of EvilBible.com <Dont_Reply@Here.com> wrote:
"david ford" <dford3@gl.umbc.edu> wrote in message
news:b1c67abe.0404272017.3fb911d4@posting.google.com...
I don't particularly care about the tautology objection to the theory
of natural selection. However, the essay below deals with a T.O. FAQ
and might be of interest.
Perhaps you don't care for the tautology objection to the theory of natural
selection because it is totally bogus. Why bother posting something you
know is incorrect?
Because that is was David does.
Perhaps someone could chase John Wilkins down and get his rebuttal of
the essay's points.
.
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| User: "Augray" |
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| Title: Re: "A Good Tautology is Hard to Avoid" |
01 May 2004 07:30:49 PM |
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On Thu, 29 Apr 2004 03:43:53 +0000 (UTC), (david
ford) wrote in <b1c67abe.0404281947.dd02778@posting.google.com>:
AC <mightymartianca@hotmail.com> wrote in message news:<slrnc8vnb2.3d0.mightymartianca@alder.alberni.net>...
On Wed, 28 Apr 2004 16:14:02 +0000 (UTC),
Editor of EvilBible.com <Dont_Reply@Here.com> wrote:
"david ford" < > wrote in message
news:b1c67abe.0404272017.3fb911d4@posting.google.com...
I don't particularly care about the tautology objection to the theory
of natural selection. However, the essay below deals with a T.O. FAQ
and might be of interest.
Perhaps you don't care for the tautology objection to the theory of natural
selection because it is totally bogus. Why bother posting something you
know is incorrect?
Because that is was David does.
Perhaps someone could chase John Wilkins down and get his rebuttal of
the essay's points.
Given his post at
http://www.google.com/groups?selm=1gb3zey.1548km51v4sma6N%25john_SPAM%40wilkins.id.au
that's unlikely.
.
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| User: "R.Schenck" |
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| Title: Re: "A Good Tautology is Hard to Avoid" |
28 Apr 2004 10:21:58 PM |
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(david ford) on 28 Apr 2004 posted
snip
wait. Isn't the subject line a tautology? Are you defining the good
tautologies as the ones that are hard to avoid and the ones that are hard
to avoid as the good ones?
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| User: "david ford" |
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| Title: A response Re: "A Good Tautology is Hard to Avoid" |
28 May 2004 07:29:46 PM |
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(david ford) wrote in "Re: "A Good Tautology is
Hard to Avoid"" in message
news:<b1c67abe.0404272017.3fb911d4@posting.google.com>...
I don't particularly care about the tautology objection to the theory
of natural selection. However, the essay below deals with a T.O. FAQ
and might be of interest.
Eric Anderson, "A Good Tautology is Hard to Avoid"
http://www.evolutiondebate.info/A%20Good%20Tautology%20is%20Hard%20to%20Avoid.htm
[snip]
On
http://www.evolutiondebate.info
the "Further Thoughts on Natural Selection" link is to a PDF file in
which Eric Anderson has some responses to comments made by the
following individuals:
Ferrous Patella, Alan Jeffery, Ian Braidwood, Thomas Faller, Frank J.,
Howard Hershey.
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| User: "Bill Rogers" |
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| Title: Re: "A Good Tautology is Hard to Avoid" |
28 Apr 2004 07:42:11 AM |
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(david ford) wrote in message news:<b1c67abe.0404272017.3fb911d4@posting.google.com>...
I don't particularly care about the tautology objection to the theory
of natural selection. However, the essay below deals with a T.O. FAQ
and might be of interest.
Eric Anderson, "A Good Tautology is Hard to Avoid"
http://www.evolutiondebate.info/A%20Good%20Tautology%20is%20Hard%20to%20Avoid.htm
<snip only to save electrons>
Conclusion
The concept of natural selection as proposed by Darwin, and as often
applied today, is likely a tautology. The only way for us to keep it
from failing as a tautology is to carefully define fitness in terms of
characteristics that are independent of survivability. And once saved
from this logical precipice, the only way to give natural selection
any real explanatory substance is to come up with a concrete working
definition of fitness that can be tested. Although various vague
characteristics have been proposed, such as efficiency, it has been
notoriously difficult to pin down any useful working definition of
fitness over the past century and a half. Without such a definition,
we cannot carry out meaningful empirical test to determine the
correctness of the hypothesis.
Given the difficulties of defining fitness in a meaningful way, a word
play on the title of Wilkins' article might provide us with an
appropriate motto for evolutionary theory today: "A Good Tautology is
Hard to Avoid."
I think that you are correct that there is a danger of natural
selection becoming a tautology. But I also think you may have
misunderstood the analogy to F=ma. One could well argue that it is
tautological to answer the question "what is a force?" by saying, "a
force is something that imparts an acceleration, a, to something else
which has mass, m." That law of Newton is not tautological in that it
provides motivation for a whole field of physics. It predicts that, if
you think you know what the forces acting on something are, and if you
work out what they are like, and if it still appears that f does not
equal ma, then you must be overlooking something. It is very practical
and experimentally based. The statement F=ma is, in a way, a challenge
to understand and define just what you mean by a force, be it
gravitational, electromagnetic, frictional, or what have you. It would
only be a tautology if physicists stopped work when they had measured
a body's acceleration and declared "Ah, the force is m times a, we
know what the force is. We are done."
In the same way, if a biologist says "This organism is here, so it has
survived natural selection, so it is fit. End of story, we have now
understood its fitness," he would be treating natural selection as a
tautology. On the other hand, if he tries to understand the actual
basis of the organism's fitness in its environment, then he is using a
non-tautological law of natural selection to deepen his understanding
of biological fitness.
Of course, since you are not Eric Anderson, you may not feel up to
defending the article you posted on his behalf.
Bill
Eric Anderson
July 18, 2003
===========================================================
For Further Reading
Brady and Waddington on tautology
http://www.google.com/groups?selm=Pine.LNX.4.10A.B3.9910102327070.29158-100000%40jabba.gl.umbc.edu
Grene on Schindewolf; Margulis; Calder; Gould on hogwash in
evolutionary theory
http://www.google.com/groups?selm=Pine.SGI.3.95.970721233453.16211D-100000%40umbc9.umbc.edu
Rosen
http://www.google.com/groups?selm=Pine.SGI.3.96A.980913231459.8446A-100000%40umbc8.umbc.edu
.
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| User: "Mike Goodrich" |
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| Title: Re: "A Good Tautology is Hard to Avoid" |
28 Apr 2004 08:53:09 AM |
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Bill Rogers wrote:
dford3@gl.umbc.edu (david ford) wrote in message news:<b1c67abe.0404272017.3fb911d4@posting.google.com>...
I don't particularly care about the tautology objection to the theory
of natural selection. However, the essay below deals with a T.O. FAQ
and might be of interest.
Eric Anderson, "A Good Tautology is Hard to Avoid"
http://www.evolutiondebate.info/A%20Good%20Tautology%20is%20Hard%20to%20Avoid.htm
<snip only to save electrons>
Conclusion
The concept of natural selection as proposed by Darwin, and as often
applied today, is likely a tautology. The only way for us to keep it
from failing as a tautology is to carefully define fitness in terms of
characteristics that are independent of survivability. And once saved
from this logical precipice, the only way to give natural selection
any real explanatory substance is to come up with a concrete working
definition of fitness that can be tested. Although various vague
characteristics have been proposed, such as efficiency, it has been
notoriously difficult to pin down any useful working definition of
fitness over the past century and a half. Without such a definition,
we cannot carry out meaningful empirical test to determine the
correctness of the hypothesis.
Given the difficulties of defining fitness in a meaningful way, a word
play on the title of Wilkins' article might provide us with an
appropriate motto for evolutionary theory today: "A Good Tautology is
Hard to Avoid."
I think that you are correct that there is a danger of natural
selection becoming a tautology. But I also think you may have
misunderstood the analogy to F=ma. One could well argue that it is
tautological to answer the question "what is a force?" by saying, "a
force is something that imparts an acceleration, a, to something else
which has mass, m." That law of Newton is not tautological in that it
provides motivation for a whole field of physics. It predicts that, if
you think you know what the forces acting on something are, and if you
work out what they are like, and if it still appears that f does not
equal ma, then you must be overlooking something. It is very practical
and experimentally based. The statement F=ma is, in a way, a challenge
to understand and define just what you mean by a force, be it
gravitational, electromagnetic, frictional, or what have you. It would
only be a tautology if physicists stopped work when they had measured
a body's acceleration and declared "Ah, the force is m times a, we
know what the force is. We are done."
In the same way, if a biologist says "This organism is here, so it has
survived natural selection, so it is fit. End of story, we have now
understood its fitness," he would be treating natural selection as a
tautology. On the other hand, if he tries to understand the actual
basis of the organism's fitness in its environment, then he is using a
non-tautological law of natural selection to deepen his understanding
of biological fitness.
Of course, since you are not Eric Anderson, you may not feel up to
defending the article you posted on his behalf.
Bill
I think you have the wrong idea about F=mA (where I am using caps to
denote vectors.)
First off in general,
F <> mA
but instead
F = (d/dt) P
where P is the momentum vector.
A rocketry problem where the mass is not constant is the typical example.
Further A is *not defined* in terms of F which is the important point
but rather
A = (d^2/dt^2) R
where R is the position vector.
Also note that F<>0 for a *particular* force for a body for which
(d^2/dt^2) R=0.
Only the net force is zero.
Thus a *particular* force (e.g., the electrostatic force ) is *not*
defined in terms of acceleration,
Nor is accelration defined in terms of force as previously shown.
Thus F=mA is clearly not tautalogical, but is an equivalence which is
true under certain conditions.
regards,
-Mike Goodrich
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| User: "Tracy Hamilton" |
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| Title: Re: "A Good Tautology is Hard to Avoid" |
28 Apr 2004 11:49:33 AM |
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"Mike Goodrich" <goodrich_ms@yahoo.com> wrote in message
news:408F9E94.2050009@yahoo.com...
Bill Rogers wrote:
dford3@gl.umbc.edu (david ford) wrote in message
news:<b1c67abe.0404272017.3fb911d4@posting.google.com>...
I don't particularly care about the tautology objection to the theory
of natural selection. However, the essay below deals with a T.O. FAQ
and might be of interest.
Eric Anderson, "A Good Tautology is Hard to Avoid"
http://www.evolutiondebate.info/A%20Good%20Tautology%20is%20Hard%20to%20Av
oid.htm
<snip only to save electrons>
Conclusion
The concept of natural selection as proposed by Darwin, and as often
applied today, is likely a tautology. The only way for us to keep it
from failing as a tautology is to carefully define fitness in terms of
characteristics that are independent of survivability. And once saved
Wrong. All that it needs is just not be *defined* in terms of survival.
from this logical precipice, the only way to give natural selection
any real explanatory substance is to come up with a concrete working
definition of fitness that can be tested. Although various vague
characteristics have been proposed, such as efficiency, it has been
notoriously difficult to pin down any useful working definition of
fitness over the past century and a half.
The characteristics are not vague - it is the relation of the probability
of survival to those characteristics that is *difficult* to
do quantitatively. I agree that if it were easy to do, then making
iron-clad arguments would be much easier.
Without such a definition,
we cannot carry out meaningful empirical test to determine the
correctness of the hypothesis.
Not really. One could hypothesize for example that melanism
(is color really vague?) and bird predation is responsible for the
natural selection, and do tests.
It is indeed the case that there are untested scenarios of natural selection
(just-so stories) that sound good, but may have alternative ones that sound
just as good,
or there may have been no selection at all (only paid lip service by
pan-adaptionists)!
Given the difficulties of defining fitness in a meaningful way, a word
play on the title of Wilkins' article might provide us with an
appropriate motto for evolutionary theory today: "A Good Tautology is
Hard to Avoid."
I think that you are correct that there is a danger of natural
selection becoming a tautology. But I also think you may have
misunderstood the analogy to F=ma. One could well argue that it is
tautological to answer the question "what is a force?" by saying, "a
force is something that imparts an acceleration, a, to something else
which has mass, m." That law of Newton is not tautological in that it
provides motivation for a whole field of physics. It predicts that, if
you think you know what the forces acting on something are, and if you
work out what they are like, and if it still appears that f does not
equal ma, then you must be overlooking something. It is very practical
and experimentally based. The statement F=ma is, in a way, a challenge
to understand and define just what you mean by a force, be it
gravitational, electromagnetic, frictional, or what have you. It would
only be a tautology if physicists stopped work when they had measured
a body's acceleration and declared "Ah, the force is m times a, we
know what the force is. We are done."
In the same way, if a biologist says "This organism is here, so it has
survived natural selection, so it is fit. End of story, we have now
understood its fitness," he would be treating natural selection as a
tautology. On the other hand, if he tries to understand the actual
basis of the organism's fitness in its environment, then he is using a
non-tautological law of natural selection to deepen his understanding
of biological fitness.
Of course, since you are not Eric Anderson, you may not feel up to
defending the article you posted on his behalf.
Bill
I think you have the wrong idea about F=mA (where I am using caps to
denote vectors.)
You mean, if something was framed as a tautology, it would not necessarily
BE a tautology? Kind of makes you wonder if scientific theories
purported to be tautological really are, doesn't it?
[snip discussion]
Thus F=mA is clearly not tautalogical, but is an equivalence which is
true under certain conditions.
Tracy P. Hamilton
.
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| User: "Mike Goodrich" |
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| Title: Re: "A Good Tautology is Hard to Avoid" |
28 Apr 2004 02:47:40 PM |
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Tracy Hamilton wrote:
"Mike Goodrich" <goodrich_ms@yahoo.com> wrote in message
news:408F9E94.2050009@yahoo.com...
Bill Rogers wrote:
dford3@gl.umbc.edu (david ford) wrote in message
news:<b1c67abe.0404272017.3fb911d4@posting.google.com>...
I don't particularly care about the tautology objection to the theory
of natural selection. However, the essay below deals with a T.O. FAQ
and might be of interest.
Eric Anderson, "A Good Tautology is Hard to Avoid"
http://www.evolutiondebate.info/A%20Good%20Tautology%20is%20Hard%20to%20Av
oid.htm
<snip only to save electrons>
Conclusion
The concept of natural selection as proposed by Darwin, and as often
applied today, is likely a tautology. The only way for us to keep it
from failing as a tautology is to carefully define fitness in terms of
characteristics that are independent of survivability. And once saved
Wrong. All that it needs is just not be *defined* in terms of survival.
from this logical precipice, the only way to give natural selection
any real explanatory substance is to come up with a concrete working
definition of fitness that can be tested. Although various vague
characteristics have been proposed, such as efficiency, it has been
notoriously difficult to pin down any useful working definition of
fitness over the past century and a half.
The characteristics are not vague - it is the relation of the probability
of survival to those characteristics that is *difficult* to
do quantitatively. I agree that if it were easy to do, then making
iron-clad arguments would be much easier.
Without such a definition,
we cannot carry out meaningful empirical test to determine the
correctness of the hypothesis.
Not really. One could hypothesize for example that melanism
(is color really vague?) and bird predation is responsible for the
natural selection, and do tests.
It is indeed the case that there are untested scenarios of natural selection
(just-so stories) that sound good, but may have alternative ones that sound
just as good,
or there may have been no selection at all (only paid lip service by
pan-adaptionists)!
Given the difficulties of defining fitness in a meaningful way, a word
play on the title of Wilkins' article might provide us with an
appropriate motto for evolutionary theory today: "A Good Tautology is
Hard to Avoid."
I think that you are correct that there is a danger of natural
selection becoming a tautology. But I also think you may have
misunderstood the analogy to F=ma. One could well argue that it is
tautological to answer the question "what is a force?" by saying, "a
force is something that imparts an acceleration, a, to something else
which has mass, m." That law of Newton is not tautological in that it
provides motivation for a whole field of physics. It predicts that, if
you think you know what the forces acting on something are, and if you
work out what they are like, and if it still appears that f does not
equal ma, then you must be overlooking something. It is very practical
and experimentally based. The statement F=ma is, in a way, a challenge
to understand and define just what you mean by a force, be it
gravitational, electromagnetic, frictional, or what have you. It would
only be a tautology if physicists stopped work when they had measured
a body's acceleration and declared "Ah, the force is m times a, we
know what the force is. We are done."
In the same way, if a biologist says "This organism is here, so it has
survived natural selection, so it is fit. End of story, we have now
understood its fitness," he would be treating natural selection as a
tautology. On the other hand, if he tries to understand the actual
basis of the organism's fitness in its environment, then he is using a
non-tautological law of natural selection to deepen his understanding
of biological fitness.
Of course, since you are not Eric Anderson, you may not feel up to
defending the article you posted on his behalf.
Bill
I think you have the wrong idea about F=mA (where I am using caps to
denote vectors.)
You mean, if something was framed as a tautology, it would not necessarily
BE a tautology? Kind of makes you wonder if scientific theories
purported to be tautological really are, doesn't it?
[snip discussion]
No, obviously I meant that F=mA is not framed as a tautology!
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| User: "Tracy Hamilton" |
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| Title: Re: "A Good Tautology is Hard to Avoid" |
28 Apr 2004 03:29:10 PM |
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"Mike Goodrich" <goodrich_ms@yahoo.com> wrote in message
news:408FF2A5.4090005@yahoo.com...
Tracy Hamilton wrote:
You mean, if something was framed as a tautology, it would not
necessarily
BE a tautology? Kind of makes you wonder if scientific theories
purported to be tautological really are, doesn't it?
[snip discussion]
No, obviously I meant that F=mA is not framed as a tautology!
Indeed it is not in fact a tautology, once you explain why it is not.
But someone not in the know, or with an anti-Newtonian agenda
could certainly claim it was a tautology, and make it sound like one
by omission.
Tracy P. Hamilton
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| User: "David Murdock" |
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| Title: Re: "A Good Tautology is Hard to Avoid" |
28 Apr 2004 03:32:42 PM |
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Mike Goodrich <goodrich_ms@yahoo.com> wrote in message news:<408F9E94.2050009@yahoo.com>...
Bill Rogers wrote:
I think that you are correct that there is a danger of natural
selection becoming a tautology. But I also think you may have
misunderstood the analogy to F=ma. One could well argue that it is
tautological to answer the question "what is a force?" by saying, "a
force is something that imparts an acceleration, a, to something else
which has mass, m."
[snip]
Bill
I think you have the wrong idea about F=mA (where I am using caps to
denote vectors.)
First off in general,
F <> mA
but instead
F = (d/dt) P
where P is the momentum vector.
There is no difference.
I see this claim occasionally, but for non-relativistic classical
physics where we don't get into the idea of relativistic mass, it's
wrong. Within that context, the mass of a particle does not change
and F=ma has exactly the same content. If you've got an example of
vanishing mass for which one would even consider applying Newtonian
physics, I'd love to hear about it.
A rocketry problem where the mass is not constant is the typical example.
No, that is not such a case. A rocket works because it spews mass out
the rear end, not because the mass is simply vanishing. The mass of
the rocket plus the stuff it has ejected remains the same; it is only
sometimes *called* a system of variable mass since the mass of the
*useful* section is changing.
Now it is true that for such a problem involving multiple unspecified
particles and unknown forces Newton's second law may be hard to apply,
and the third law is more useful, but that does not mean that mass is
simply *vanishing*. The dm/dt that shows up in the solution is just
the rate at which the mass of the useful portion is becoming
non-useful. The solution must also include the speed with which the
gas is expelled.
When I have two masses fly apart from a spring that is compressed
between them, no one would call that a system where mass is
"changing". It is no different with a rocket and its propellant.
---DPM
[snip rest]
regards,
-Mike Goodrich
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| User: "Mike Goodrich" |
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| Title: Re: "A Good Tautology is Hard to Avoid" |
29 Apr 2004 08:45:22 AM |
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David Murdock wrote:
Mike Goodrich <goodrich_ms@yahoo.com> wrote in message news:<408F9E94.2050009@yahoo.com>...
Bill Rogers wrote:
I think that you are correct that there is a danger of natural
selection becoming a tautology. But I also think you may have
misunderstood the analogy to F=ma. One could well argue that it is
tautological to answer the question "what is a force?" by saying, "a
force is something that imparts an acceleration, a, to something else
which has mass, m."
[snip]
Bill
I think you have the wrong idea about F=mA (where I am using caps to
denote vectors.)
First off in general,
F <> mA
but instead
F = (d/dt) P
where P is the momentum vector.
There is no difference.
I see this claim occasionally, but for non-relativistic classical
physics where we don't get into the idea of relativistic mass, it's
wrong. Within that context, the mass of a particle does not change
and F=ma has exactly the same content. If you've got an example of
vanishing mass for which one would even consider applying Newtonian
physics, I'd love to hear about it.
A rocketry problem where the mass is not constant is the typical example.
No, that is not such a case. A rocket works because it spews mass out
the rear end, not because the mass is simply vanishing. The mass of
the rocket plus the stuff it has ejected remains the same; it is only
sometimes *called* a system of variable mass since the mass of the
*useful* section is changing.
Now it is true that for such a problem involving multiple unspecified
particles and unknown forces Newton's second law may be hard to apply,
and the third law is more useful, but that does not mean that mass is
simply *vanishing*. The dm/dt that shows up in the solution is just
the rate at which the mass of the useful portion is becoming
non-useful. The solution must also include the speed with which the
gas is expelled.
When I have two masses fly apart from a spring that is compressed
between them, no one would call that a system where mass is
"changing". It is no different with a rocket and its propellant.
---DPM
[snip rest]
In anal;ytical mechanics there is nothing to preclude us from
considering a "system" of variable mass as a very good approximation of
a situation in which the mass which is being subjected to some applied
force is in fact changing continuously. We are also free to restrict
our attention to the mass system of interest - such as a rocket with its
remaining propellant - albeit variable, and ignore the ejected mass from
further consideration.
Thus we are lead naturally to a formulation like F = (d/dt) (MV), where
we allow for both M and V to be continously variable as the least
restrictive case, and which reduces to F = mA for "particles' which by
definition have indivisible mass and systems of particles which due
typically to 'internal' forces are held together.
There is no loss of generality to say F = (d/dt) P.
All of this speaking classically of course.
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| User: "Bill Rogers" |
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| Title: Re: "A Good Tautology is Hard to Avoid" |
30 Apr 2004 02:53:07 AM |
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Mike Goodrich <goodrich_ms@yahoo.com> wrote in message news:<408F9E94.2050009@yahoo.com>...
Bill Rogers wrote:
dford3@gl.umbc.edu (david ford) wrote in message news:<b1c67abe.0404272017.3fb911d4@posting.google.com>...
<snip>> >
I think that you are correct that there is a danger of natural
selection becoming a tautology. But I also think you may have
misunderstood the analogy to F=ma. One could well argue that it is
tautological to answer the question "what is a force?" by saying, "a
force is something that imparts an acceleration, a, to something else
which has mass, m." That law of Newton is not tautological in that it
provides motivation for a whole field of physics. It predicts that, if
you think you know what the forces acting on something are, and if you
work out what they are like, and if it still appears that f does not
equal ma, then you must be overlooking something. It is very practical
and experimentally based. The statement F=ma is, in a way, a challenge
to understand and define just what you mean by a force, be it
gravitational, electromagnetic, frictional, or what have you. It would
only be a tautology if physicists stopped work when they had measured
a body's acceleration and declared "Ah, the force is m times a, we
know what the force is. We are done."
<snip> >
Bill
I think you have the wrong idea about F=mA (where I am using caps to
denote vectors.)
No, I have a pretty good understanding of mechanics. I put the second
law in the form in which it is easiest to explain why it is not a
tautology. You are certainly free to rewrite it in vector form, or to
focus your attention on the "interesting" part of a system of masses
and consider force as equal to dP/dt, to break up a net force into
components, and even to take relativistic effects into account, if you
want. None of that affects the explanation of why the second law is
non-tautological.
Or the aptness of the analogy to survival of the fittest, which also
is not a tautology.
First off in general,
F <> mA
but instead
F = (d/dt) P
where P is the momentum vector.
A rocketry problem where the mass is not constant is the typical example.
Further A is *not defined* in terms of F which is the important point
but rather
A = (d^2/dt^2) R
where R is the position vector.
Also note that F<>0 for a *particular* force for a body for which
(d^2/dt^2) R=0.
Only the net force is zero.
Thus a *particular* force (e.g., the electrostatic force ) is *not*
defined in terms of acceleration,
Nor is accelration defined in terms of force as previously shown.
Thus F=mA is clearly not tautalogical, but is an equivalence which is
true under certain conditions.
regards,
-Mike Goodrich
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| User: "Mike Goodrich" |
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| Title: Re: "A Good Tautology is Hard to Avoid" |
30 Apr 2004 08:24:40 AM |
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Bill Rogers wrote:
Mike Goodrich <goodrich_ms@yahoo.com> wrote in message news:<408F9E94.2050009@yahoo.com>...
Bill Rogers wrote:
dford3@gl.umbc.edu (david ford) wrote in message news:<b1c67abe.0404272017.3fb911d4@posting.google.com>...
<snip>> >
I think that you are correct that there is a danger of natural
selection becoming a tautology. But I also think you may have
misunderstood the analogy to F=ma. One could well argue that it is
tautological to answer the question "what is a force?" by saying, "a
force is something that imparts an acceleration, a, to something else
which has mass, m." That law of Newton is not tautological in that it
provides motivation for a whole field of physics. It predicts that, if
you think you know what the forces acting on something are, and if you
work out what they are like, and if it still appears that f does not
equal ma, then you must be overlooking something. It is very practical
and experimentally based. The statement F=ma is, in a way, a challenge
to understand and define just what you mean by a force, be it
gravitational, electromagnetic, frictional, or what have you. It would
only be a tautology if physicists stopped work when they had measured
a body's acceleration and declared "Ah, the force is m times a, we
know what the force is. We are done."
<snip> >
Bill
I think you have the wrong idea about F=mA (where I am using caps to
denote vectors.)
No, I have a pretty good understanding of mechanics. I put the second
law in the form in which it is easiest to explain why it is not a
tautology. You are certainly free to rewrite it in vector form, or to
focus your attention on the "interesting" part of a system of masses
and consider force as equal to dP/dt, to break up a net force into
components, and even to take relativistic effects into account, if you
want. None of that affects the explanation of why the second law is
non-tautological.
Or the aptness of the analogy to survival of the fittest, which also
is not a tautology.
First off in general,
F <> mA
but instead
F = (d/dt) P
where P is the momentum vector.
A rocketry problem where the mass is not constant is the typical example.
Further A is *not defined* in terms of F which is the important point
but rather
A = (d^2/dt^2) R
where R is the position vector.
Also note that F<>0 for a *particular* force for a body for which
(d^2/dt^2) R=0.
Only the net force is zero.
Thus a *particular* force (e.g., the electrostatic force ) is *not*
defined in terms of acceleration,
Nor is accelration defined in terms of force as previously shown.
Thus F=mA is clearly not tautalogical, but is an equivalence which is
true under certain conditions.
regards,
-Mike Goodrich
F=mA is not tautological for the reasons I stated; I'm sorry you missed it.
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| User: "Ian Braidwood" |
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| Title: Re: "A Good Tautology is Hard to Avoid" |
29 Apr 2004 07:18:15 AM |
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(david ford) wrote in message news:<b1c67abe.0404272017.3fb911d4@posting.google.com>...
I don't particularly care about the tautology objection to the theory
of natural selection. However, the essay below deals with a T.O. FAQ
and might be of interest.
Eric Anderson, "A Good Tautology is Hard to Avoid"
http://www.evolutiondebate.info/A%20Good%20Tautology%20is%20Hard%20to%20Avoid.htm
Critics of evolutionary theory have long argued that the concept of
natural selection is a tautology. John Wilkins seeks to counter this
argument in his article "A Good Tautology is Hard to Find" on the
site, The Talk.Origins Archive.
Wilkins' discussion, found at
http://www.talkorigins.org/faqs/evolphil/tautology.html, contains two
points that I would like to address. The first is Wilkins' contention
that the concept of natural selection is not a tautology. The second
is his contention that natural selection rules out many possibilities,
which adds to its substantive explanatory power. Let's examine each
of these points in turn.
Tautology
In his article, Wilkins states:
"The simple version of the so-called 'tautology argument' is this:
Natural selection is the survival of the fittest. The fittest are
those that survive. Therefore, evolution by natural selection is a
tautology (a circular definition).
The real significance of this argument is not the argument itself, but
that it was taken seriously by any professional philosophers at all.
'Fitness' to Darwin meant not those that survive, but those that could
be expected to survive because of their adaptations and functional
efficiency, when compared to others in the population."
In other words, according to Wilkins, Darwin used fitness to mean not
those that did survive but those that were expected to survive. Thus
Wilkins implies that we will not have a tautology if we reword the
definition as follows: "Natural selection is survival of the fittest.
The fittest are those that are expected to survive." If natural
selection is properly doing its job of selecting, which we are assured
it always does, then those that are expected to survive will be those
that will survive. So if we take what would otherwise be a tautology
and change the verb tense, then it is no longer a tautology?
The problem is that under Wilkins' approach, natural selection will
mean nothing more than survival of those that are expected to survive,
and we are still left with a tautology. We haven't gotten anywhere by
shifting the focus from those that did survive to those that are
expected to survive. In fairness, there is a way out of the tautology
problem, as I will discuss below, but natural selection needs to be
formulated much more carefully than just proposing that we should
focus on expected survival rather than actual survival.
Anderson has missed the point here by ignoring why those who survive
do so. It is as if biologists were arguing that there is some mystical
quality of 'survivability', which of course they don't propose at all.
Those who are expected to survive will do so, because they have an
adaptaion which confers an advantage in relation to those individuals
who lack it. Thus there are independent critria by which fitness can
be defined and this saves Natural Selection from tautology.
In the peppered moth example, the darker coloured moths survived
because their colouring provided better camouflage where there were
high levels of pollution; similarly, the lighter forms flourished
where pollution was less severe. So here, fitness is defined as 'best
camouflaged' and the fact that the moths did proliferate in the
environments to which they were best suited supports Natural
Selection.
In flying insects preyed upon by bats, camouflage provides no
advantage and so can be no part of the definition of fitness, however
the ability to detect ultrasound would confer an advantage and
examples are found in nature.
Lacewings can detect bats' ultrasound. They stop beating their wings
when they hear the mammal approach and fall out of the bat's grasp.
Some moths go a step further, by actually emitting a powerful
ultrasound sigal of their own, effectively jamming the bat's sonar.
Sometimes, camouflage is the last thing you need. If you're an insect
which stores plant toxins in your body as a defense, then you need to
warn any potential predator that you're poisonous and so conspicuous
colouration is what you need.
It's clear from these examples that, depeding on context, camouflage
can aid, be irrelevant to, or actually detrimental to an organism's
fitness; so fitness means different things in different circumstances.
The word fitness is a generalisation for any quality or characteristic
which confers an advantage and its precise meaning is dependent on the
environment in which the organism in question lives.
If biologists merely accepted that any survivor had some mystical
quality of 'fitness', then the charge of tautology would be justified.
However they don't, they specify a particular characteristic which
confers an advantage to the survivour.
Regards,
(-: Ian :-)
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| User: "Ken Shaw" |
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| Title: Re: "A Good Tautology is Hard to Avoid" |
28 Apr 2004 07:57:44 AM |
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david ford wrote:
I don't particularly care about the tautology objection to the theory
of natural selection. However, the essay below deals with a T.O. FAQ
and might be of interest.
Eric Anderson, "A Good Tautology is Hard to Avoid"
http://www.evolutiondebate.info/A%20Good%20Tautology%20is%20Hard%20to%20Avoid.htm
<snip of copyrighted material>
Did you obtain permission to quote this essay in full?
So if you don't care about this nonissue why waste everyone else's
bandwidth with this essay?
Ken
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| User: "Thomas H. Faller" |
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| Title: Re: "A Good Tautology is Hard to Avoid" |
29 Apr 2004 08:17:30 AM |
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david ford wrote:
I don't particularly care about the tautology objection to the theory
of natural selection. However, the essay below deals with a T.O. FAQ
and might be of interest.
Eric Anderson, "A Good Tautology is Hard to Avoid"
http://www.evolutiondebate.info/A%20Good%20Tautology%20is%20Hard%20to%20Avoid.htm
<snip>
In other words, according to Wilkins, Darwin used fitness to mean not
those that did survive but those that were expected to survive. Thus
Wilkins implies that we will not have a tautology if we reword the
definition as follows: "Natural selection is survival of the fittest.
The fittest are those that are expected to survive." If natural
selection is properly doing its job of selecting, which we are assured
it always does, then those that are expected to survive will be those
that will survive. So if we take what would otherwise be a tautology
and change the verb tense, then it is no longer a tautology?
The problem is that under Wilkins' approach, natural selection will
mean nothing more than survival of those that are expected to survive,
and we are still left with a tautology. We haven't gotten anywhere by
shifting the focus from those that did survive to those that are
expected to survive.
So "those we observe to survive" survive is a tautology, and "those we
predict to survive according to our theory" survive is also a tautology?
What about "I get X from my experiment, according to my prediction"?
That isn't a valid way to determine if a theory is successful? I think that
Anderson has warped words to please himself, not to get at the truth.
<snipping fruitless quibble>
Ruling Out
Wilkins states:
"However, there is another, more sophisticated version [of the
tautology argument], due mainly to Karl Popper (1976: sect. 37).
According to Popper, any situation where species exist is compatible
with Darwinian explanation, because if those species were not adapted,
they would not exist. That is, Popper says, we define adaptation as
that which is sufficient for existence in a given environment.
Therefore, since nothing is ruled out, the theory has no explanatory
power, for everything is ruled in.
This is not true, as a number of critics of Popper have observed since
(eg, Stamos (1996) (note 1)). Darwinian theory rules out quite a lot.
It rules out the existence of inefficient organisms when more
efficient organisms are about. It rules out change that is
theoretically impossible (according to the laws of genetics, ontogeny,
and molecular biology) to achieve in gradual and adaptive steps (see
Dawkins (1996)). It rules out new species being established without
ancestral species."
What Wilkins is saying in effect is that because genetics, ontogeny,
molecular biology, etc. are testable hypotheses, and because natural
selection is presumed not to violate them, then natural selection
rules out violations of those natural laws, which adds to its
explanatory power.
First of all, Popper was no doubt making a practical point about the
substantial challenge of pinning down a working definition of the
causative element, and thus the practical difficulty of natural
selection teaching us anything useful. No doubt Popper would agree
that violations of natural law are not available to natural selection.
Second, with apologies to Dawkins, whom Wilkins cites, I believe a
moment's reflection will tell us that natural selection does not rule
out violations of genetics; genetics does. It does not rule out
violations of molecular biology; molecular biology does.
Bait and switch. He didn't say NS rules out violations of genetics.
He said that if genetic change is not possible in _gradual_ and
_adaptive_ steps to get from one species to another, NS will not
allow it. If you have to get from dragonfly ancestor to dragonfly
through a genetically possible intermediate with twelve wings
annd no mouth or legs, it won't happen, even if it is consistant
with genetically possible changes.
<snip more blather based on incorrect premises>
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| User: "howard hershey" |
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| Title: Re: "A Good Tautology is Hard to Avoid" |
28 Apr 2004 11:24:26 AM |
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david ford wrote:
I don't particularly care about the tautology objection to the theory
of natural selection. However, the essay below deals with a T.O. FAQ
and might be of interest.
I agree that the tautology objection to the observation that natural
selection exists is silly and is largely based on a definition that one
rarely uses or even sees anymore in standard texts (except to discuss
its defects, starting with its use of the superlative -est ending rather
than the comparative -er ending). But so is the denial that natural
selection exists as a fact of nature (based on equally silly
misunderstandings) that you express regularly and regularly conflate
with 'evolution by the mechanism of natural selection'. One does not
need to think that evolution happens to recognize that natural selection
does. Natural selection was well recognized prior to Darwin.
Natural selection is a frequently observed feature of the *interaction
between organisms and their environment*. It is the observation that
the *environment* (which is unintelligent) in which organisms live often
can, but does not inevitably do so, discriminate (in a stochastic
fashion) between *different phenotypes* of an organism living in that
environment, favoring one phenotype over the other and specifically
favoring phenotypes that are better adapted to life in that particular
environment. When it does so, the phenotype which is favored will (in
the stochastic sense of 'be more likely to' rather than the inevitable
causal sense 'must') have *greater reproductive success* than the
alternate phenotype; that is, greater reproductive success is a
consequence of being better adapted to a particular local environment.
[Of course, for evolution to be a consequence of natural selection, the
phenotypic differences that the environment discriminates between must
be a consequence, at least in part, of genetic differences. However, we
are talking solely about natural selection at this point. And natural
selection occurs just as relentlessly and ruthlessly (and
unintelligently) if the phenotypic differences are due to accident or
environment or developmental abnormality. The unintelligent
environment, as it relates to and interacts with life as a dog, will
favor the dog with four good legs and discriminate against the one with
none regardless of whether the legless condition is due to genetic
defect, accident, or developmental abnormality.]
Note the basic requirements for determining whether natural selection
has occurred: There must be *different phenotypes* that are interacting
with the *environment* relevant to that organism. Natural selection,
when it occurs under these conditions, is an observational consequence
of a comparison. Natural selection is a population phenomenon and is a
comparison of *phenotypes* and not *individuals*. Thus, one can talk
about the fitter *phenotype* but not the fitter *individuals*. The
survival of any single individual in a population may be a simple
anomoly (the environment only provides a stochastic bias, not a virtual
certainty). To declare that one *phenotype* is *fitter than* another,
one must be looking at a population average, not an individual.
Although a comparison of *different phenotypes* and their interaction
with a particular *environment* is the basic requirement for determining
whether natural selection has occurred, merely having two (or more)
different phenotypes in an environment does not guarantee that natural
selection will occur (or will have occurred). *Natural selection* is
only said to occur when one of the two phenotypes has a *statistically
significant* difference on the metric of reproductive success.
Phenotypes which do not affect nor produce a statistically significant
difference in the metric of reproductive success are *selectively*
neutral wrt one another.
******By convention, and in accordance with the common useage of the
term "fitter", the phenotype which has the significantly greater
reproductive success is called the *fitter* phenotype in that particular
enviroment. That is because reproductive success is the only
recognizable universal "goal" of or metric upon which to compare living
organisms. [You are, of course, quite free to disagree with the use of
this metric and claim that the less reproductively successful organisms
should be declared to be 'fitter'.]******
[I emphasized the above paragraph, because it is, in fact, crucial. If
one wants to argue against natural selection, one must argue against
this point. I am claiming that the only *apparent* or *scientifically
detectable* or *empirically useful* universal "goal" of *all* life on
earth is, empirically if not theologically, maximal reproductive
success. This makes reproductive success the only valid metric for
measuring natural selection and defining 'greater reproductive success'
as 'fitter' is indeed consistent with common understanding of the term
'fitter'. If one agrees with the validity of using differential
reproductive success as the metric for determining whether natural
selection occurs (or has occurred), then anytime that one observes
differential reproductive success of one phenotype relative to another
significantly greater than can be accounted for by random genetic drift,
one is observing an event due to natural selection -- that is, a
difference due to the local environment discriminating between
phenotypes. That means that even if Kettlewell had not done his
experiments, industrial melanism in moths would *still* be an example of
natural selection.]
So let's summarize: Natural selection is said to have occurred when, in
any comparison of two phenotypic variants in an organism in a specific
environment, there is a significant average difference in reproductive
success of organisms with alternate phenotypes in that environment. By
convention, the phenotype which leads to greater reproductive success is
called the 'fitter' phenotype.
It is important to realize that observing a phenotypic difference does
not, by itself, tell us which, if either, phenotype is 'fitter' in any
particular environment. One can certainly use standard engineering
reasoning (by recognizing that the goal is greater reproductive success)
to make educated guesses, but must be prepared for surpises. [For
example, longevity, if it interfers with net reproductive success as is
the case in C. elegans and many other organisms, can be less 'fit' than
quick burnout due to high reproduction early on.]
OTOH, because of the definition of 'fitter' given above, if one observes
a case in nature where one phenotype is observed to have *significantly
greater* reproductive success than an alternate phenotype, one can
reasonably infer that natural selection is involved in determining the
relative numbers of the two phenotypes both now and in the future (so
long as the environment remains constant) and look for reasons why the
local environment dumbly and unintelligently significantly favors one
phenotype over the other.
IOW, the alternative to natural selection are simply cases where there
is no selection at all. Those are the only two alternatives that exist
in nature*: No selection or selection (in a specific environment). To
say that natural selection does not occur, like you seem to, is contrary
to observed reality.
*One could, I guess, make a claim that every example of the environment
discriminating between phenotypes currently ascribed to *natural*
selection is actually *artificial* selection guided by some unknown and
unobservable intelligent agency other than man. But since all examples
of natural selection involve phenotypes that are deleterious (some to
the state of being lethal, and all in the sense of affecting
reproductive success) and show consistency with engineering principles
of better by the metric of reproductive success, I see no reason for
unnecessarily multiplying the causitive agencies and explanations here.
One of the many reasons why "Survival of the fittest." is a poor
definition of natural selection (and has been recognized as a poor
definition since Darwin's time) is that it can be (and often is) falsely
interpretable as being a description of an individual property divorced
from environment rather than a comparative description of the
interaction of a phenotype in a population with a particular
environment. That is in addition to 'survival' not being the
appropriate metric by which selection is measured.
*When* natural selection is used as biologists use it, it is an
observational fact about how organisms interact with their environment.
Namely, we say that natural selection occurs when there is a
significant difference in the metric of reproductive success because the
local environment discriminates (unintelligently) between two variant
phenotypes in an organism.
[snip stuff based on the poorest of definitions of NS]
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| User: "Ferrous Patella" |
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| Title: Re: "A Good Tautology is Hard to Avoid" |
28 Apr 2004 01:35:46 PM |
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news:b1c67abe.0404272017.3fb911d4@posting.google.com by
(david ford):
Conclusion
The concept of natural selection as proposed by Darwin, and as often
applied today, is likely a tautology. The only way for us to keep it
from failing as a tautology is to carefully define fitness in terms of
characteristics that are independent of survivability.
I do not see how NS can be a tautology. NS only claims that the more fit
*are more likely* to survive. For it to be a tautology the fitter must
*always* survive and reproduce.
We can observe that the obviously less fit do sometimes survive by sheer
dint of luck. Very fit specimens are brought down by the same.
As a thought experiment, picture a herd of antelope. One genetically
sickly member is trailing behind. Out of nowhere, a bolt of lightening
zaps the herd's alpha male. The sickly member has no superior fitness to
survive that lightening bolt (unless you want to argue that he had some
hidden ability to not ***** off Thor), yet he survived.
So there you have it. The fit do not always survive. "Survival of the
fittest" is not a tautology
--
Ferrous Patella
"Great is the guilt of an unnecessary war."
--John Adams, letter to Abigail, 1797
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