This paper does not evaluate theories of evolution or
creation.
Instead, it examines principles of logic, and develops guidelines
for how theories about origins should be compared & evaluated.
1. Comparisons and Definitions
2. The Many Meanings of
Evolution
3. The Many Meanings of
Creation
4. Comparisons that are
Logically Valid
5. Shifts of Meaning (how & how,
and why)
1. Comparisons and
Definitions
Logical Comparisons
An important principle for scientific
evaluation, logical comparison, is illustrated
by asking whether a theory proposing that John is an Olympic Weightlifter
(OW) is supported by observing that John can lift a hat and place it on his
head. Yes, the OW theory predicts that John can lift the hat, and he
does. But plausible alternative theories — like "John is a weakling" or "John
has average strength" — are also compatible with this result, so the
observation offers little support for OW.
When we see John lift a hat, the appropriate
response is "So what?" To justify a response of "Wow!", the evidence
must be more relevant (for comparing OW with competitive theories) and more
impressive. For example, if we saw John lift a heavy weight, close
to the world record, this would provide strong evidence for the plausibility
of OW, since this observation is much less compatible with the alternative
theories. The principle of logical comparison says, "To distinguish
between these competitive theories, we must focus on their differences (they
disagree about John's ability to lift the near-record weight), not their
similarities (they all agree that John can lift the hat)."
This principle of logic is often ignored
when origins theories are evaluated. Instead of using logical comparisons,
scientists and educators often claim support for evolution because "it can
lift hats" instead of focusing their attention on questions that are more
challenging (for evolution) and more useful (for evaluation). A framework
for logically comparing origins theories is outlined in Section 4.
Precise Definitions
We cannot logically compare theories
unless each theory is precisely defined. In science and education,
we can improve the accuracy of our thinking and communication by using two
important words — evolution and creation — with precision and
consistency. Since each of these words can have many meanings, confusion
is possible. But if we decide that confusion is undesirable, we can
use precise definitions that minimize the possibilities for confusion and
misunderstanding. This worthy goal is the focus of Sections 2 and 3:
The Many Meanings of Evolution, and The Many Meanings of Creation. Then,
building on this foundation of conceptual clarity, a framework for logically
comparing origins theories is outlined in Section 4.
notes:
The
perils of imprecise definitions are illustrated by a sneaky
car salesman who buys your seat cover for $1000 and sells you a new
Porsche for $5000. Did
you get a good deal?
The "Olympic
Weightlifter" illustration
is borrowed from a prominent philosopher, Elliott Sober, who is a critic
of Intelligent Design.
2.
The Many Meanings of Evolution
To logically evaluate evolution, we
must carefully define each concept that is called "evolution" and critically
examine the relationships between these concepts.
In general, evolution is any
process of gradual change. In biology, evolution (E)
is a change in the gene pool of a population. But "evolution" can
also refer to fossil progression, common
descent, micro-E within a species, macro-E to
produce a new species (*), neo-Darwinian subtheories proposing
that E occurs by specific mechanisms — involving the production of
genetic variation,
expression
of
genetic variation in individuals, change of gene frequencies
in a population, and
production of new species, plus macro-evolutionary scenarios (details) — or
a Total
Macro-E claim that all biodiversity and biocomplexity was produced
by the cumulative effects of natural macro-E. { In addition,
a nonscientific meaning of E is a claim — made by some atheists
(Richard Dawkins,...) and some Christians — that "evolution
is inerently atheistic" so theistic
evolution is impossible. }
* macro-evolution can range from minor
macro-E (which occurs, for example, when two groups within a species
become isolated from each other, then evolve independently until they can
no longer interbreed, thus forming two species that are very similar) to major
macro-E.
In our pursuit of conceptual clarity,
one option is to replace the word "evolution" (which has many meanings) with
many words (each with one meaning), as I've done above. In this context
the goal of conceptual clarity is to be certain, each time "evolution" is
discussed or evaluated, that the meaning is precise and clear.
In Section 4, we'll examine four
types of evolution that can be components in an origins theory: 1)
small-scale E (micro-E and minor macro-E); 2)
an old
earth with fossil progressions; 3)
full common descent; 4) Total
Macro-E by natural mechanisms.
3.
The Many Meanings of Creation
In a common cultural stereotype, there
is one Judeo-Christian theory of creation.
In reality, four basic creation theories
are compatible with a basic Judeo-Christian doctrine of theistic creation:
In young-earth
creation (yeC), everything in the universe was miraculously created
in a 144-hour period less than 10,000 years ago. Later, most of the
earth's geology and fossil record were formed in a global flood.
In old-earth
creation (oeC),
also called progressive creation, at various times during a long history
of nature (spanning billions of years) God used miraculous-appearing theistic
action
to create. There
are two kinds of oeC: oeCindependent proposes
independent creations "from scratch" so a new species would not necessarily
have any relationships with previously existing species; oeCmodification proposes
creation by an extensive modification (by changing, adding, or deleting)
of the genetic material for some members (or all members) of an existing
species. Each type of oeC proposes a history that combines miraculous-appearing
creations (independent or by modification) with natural-appearing evolution.
In theistic
evolution (TE),
also called evolutionary creation, natural evolution
was God's method of creation, with the universe designed so complex life
would naturally evolve. Theistic
Evolution
and Theology
A design
theory is
not a creation theory. A theory of intelligent design, which claims that
a particular feature was produced by design-directed
action rather than undirected natural process,
is restricted to claims that that can be scientifically evaluated. A
basic design theory does not claim that, based on scientific analysis, we can
distinguish between supernatural design-action (in creation)
and natural design-action (in non-creation),
it just claims that "design-directed action did occur." All theories
of divine creation propose
some type of intelligent design, but in our current culture a theory of Intelligent
Design usually
has
a
narrower
definition,
as explained in Four Types of Design.
Here is a simple
analysis of relationships between the narrow-definition
Intelligent Design (in science) and creation (in theology):
• a creationist can accept a
totally
natural
evolution
with non-Design (science) and propose evolutionary creation (science + theology),
or
• a creationist can reject a
totally
natural evolution and accept Design
(science) and propose progressive creation (science + theology), or
• a person can reject a totally
natural evolution and accept Design
(science) and say "I don't know" or "I'm not going to tell you" when
asked about
creation (theology).
What is my position? I'm flexible and willing to change, but currently I think the most plausible creation theories in biology are "independent creation of the first life, then old-earth creation by genetic modification," because the most credible scientific theories include some design-directed action. But the purpose of this page is to show how all theories, not just my own, should be logically compared and evaluated.
4.
Logical Comparisons of Origins Theories
The table below lists four components
of evolutionary theory (described in Section 2) and shows whether each creation
theory affirms this component (YES) or denies it (no). This lets you
see the similarities and differences between neo-Darwinian "totally natural
evolution" (atheistic, agnostic, or theistic) and three modern creation theories,
plus outdated creation theories from two centuries ago.
theory components (for each type of E, does a theory say yes or no?) |
totally natural evolution |
old-earth creation by modification |
old-earth independent creation |
young-earth independent creation |
creation theories of 1800 |
micro-E and minor macro-E | YES | YES | YES | YES | no |
old earth with basic fossil-E | YES |
YES |
YES |
no |
no |
full common descent |
YES
|
YES | no | no | no |
natural Total Macro-E | YES | no | no | no | no |
This table uses accurate
definitions of 4 modern theories, and allows logical
comparisons:
All modern theories agree (YES YES YES
YES) about "micro-E and minor macro-E" so evidence for micro-E and minor
macro-E does not help us distinguish between neo-Darwinian evolution and
any of the three modern creationist theories. And evidence for an old
earth (with evolutionary fossil progressions) is not evidence against the
two old-earth theories, which say "YES YES".
Similarly, evidence for common descent
(such as homologous adaptations of previously existing structures, vestigial
structures, "molecular clock" analyses, and a sharing of pseudogenes, Hox
genes, and genetic code) can count against one old-earth theory (with independent
creation) but not another (with creation by genetic modification). {
All modern creationists accept partial common descent,
but some say "no" to a claim about full common
descent. } Are design and descent compatible?
Obviously, logical comparison
is important. To
distinguish between two theories, we must focus on evidence about disputed
components (where one theory says yes and the other says no), not shared
components (where both say yes, or both say no). For example, the table
above shows that most "evidence for evolution" (for minor macro-E, old-earth
fossil progressions, and full common descent) is not evidence for Total Macro-E
when
it is compared with old-earth creation by genetic modification.
In this table the information above is arranged in a different way, to clearly show — for each comparison of two theories — the disputed components (in black) that should be the focus of attention, and the shared components (in gray) that are not relevant:
What
ideas should
(and should not) be compared in each two-theory comparison? |
The two theories
that are being compared
agree about the GRAY components, but disagree about the BLACK components. |
|||
evolution |
oeC-mod
|
oeC-indep
|
yeC-indep
|
|
evolution:
totally natural evolution of all organisms |
o
|
micro-E
old earth descent total E |
micro-E
old earth descent total E |
micro-E
old earth descent total E |
oeC-modification:
old-earth creation (by macromutation of genetic material) |
o
|
micro-E
old earth descent total E |
micro-E
old earth descent total E |
|
oeC-independent:
old-earth creation (with independent creations) |
o
|
micro-E
old earth descent total E |
||
yeC-independent:
young-earth creation (with independent creations ) |
o
|
note: This table oversimplifies some relationships. For example, oeC-independent and yeC-independent will disagree in some details of their theory-based predictions (about data that is currently unknown) and retroductions (to explain data that is already known) regarding minor macro-E, but "micro-E" is GRAY because the existence of micro-E (and minor macro-E) is consistent with either theory.
5. Shifts of Meaning (how & how, and why)
How to Produce a Shift
• evolution-shifts: Often,
support is illogically shifted from a strongly supported meaning of evolution — such
as basic "old earth" progressions in the fossil record, micro-E changes (like
those that produce drug-resistant bacteria), or minor macro-E (that produces
a new-yet-similar species) — to a less strongly supported meaning (like
Total Macro-E).
• creation-shifts: Evidence
against young-earth creation is often shifted onto old-earth creation. {
What are the practical results in education? } And
the important scientific differences between two old-earth theories — independent
creation and genetic modification — are
ignored.
With an evolution-shift the implied
support for evolution increases, and with a creation-shift the implied support
for creation decreases. But in each case the shift (and associated
implication) is not logically justified.
How to Avoid a Shift
• minimizing evolution-shifts: Each
evolutionary sub-theory (as described in Section 2) is
supported by different evidence, and should have different plausibility. We
need conceptual clarity; the sub-theories of evolution should be precisely
defined and their relationships should be carefully analyzed, because if
there is only "evolution" it is easy to assume that evidence for some aspects
of evolution necessarily provides strong support for other aspects. When
we estimate the plausibility of an extrapolation from micro-E to Total Macro-E,
there should be a rigorous evaluation for each step connecting the intermediate
levels. This evaluation should be based on tight logic, not loose language
that allows a transfer of support from one level to another. { Perhaps
advocates of evolution can make a strong case for moving from lower levels
of E to Total Macro-E, but the process of "extrapolating between levels" should
be explicitly recognized. }
• minimizing creation-shifts: We
should understand what each creation theory proposes, then compare these
theories with each other and with theories of evolution, to see where they
agree and disagree. In a comparative evaluation we should focus on
the differences between competitive theories, instead of wasting time on
questions where both theories agree. When we ask, "Does this evidence
really matter?", we see that most of the evidence typically proposed in
support of evolution is irrelevant when comparing Total Macro-E with old-earth
creation by genetic modification or with a basic theory of intelligent design.
strong
support for Total Macro-E requires strong answers (but not proof) for tough
questions:
1. For each step in a macro-E
scenario, how many mutations and how much selection would be required, how
long would this
take,
and how
probable
is it? {more about rates and
complexity}
2. Could a step-by-step process
of evolution produce systems that seem irreducibly
complex (because
all parts seem necessary for performing the system's function) since there
would
be no function to "select for" until all parts are present? Are
questions allowed?
another
question, related to irreducible complexity, is even more challenging:
X. Could a nonliving system
naturally achieve the minimal complexity required
to replicate itself and thus become capable of changing, in successive generations,
by neo-Darwinian evolution? For the past
five decades,
scientists have been learning that what is required for
life seems much greater than what is possible by
natural
process. { This question is "X" because it's separate
from neo-Darwinian theory, which simply assumes the existence of an organism
that could reproduce,
and doesn't try to explain
how the first living organism became alive. } { more
about the first
life }
Why do shifts occur?
Shifts of meaning can arise from an
intention to mislead, inadequate understanding of concepts, lack of communication
skill, or (in one type of shift) a narrow focus on the most vocal form of
creationism.
But value judgments (about the relative
importance of various evaluation criteria) can also provide a logical reason
to ignore distinctions between theories. For example, if a young earth
is all that matters, all old-earth theories will be opposed with equal vigor
because their differences will seem less important than their old-earth similarities. And
for someone whose main goal is to avoid any implication that God has "interfered
with nature," all creationist theories are equally guilty.
Value judgments are an essential part
of making decisions, but they should be logically analyzed to determine whether
they are contributing to inaccurate scientific evaluations.
The Main Theme
of Sections 1-5
The quality of our thinking and evaluating,
in science and education, will improve when we use precise definitions and
logical comparisons, when we accurately understand all theories, explicitly
acknowledge their similarities and differences, and use this knowledge in
our evaluations and communications.
This page
is a condensed summary of an
older full-length page and is further condensed in FAQs: basic & medium &
short.
APPENDIX Precise
Definitions mechanistic
theories of evolution propose specific natural causes of evolution. In neo-Darwinian
theories, Darwin's basic ideas are combined with modern genetics,
mathematical population analysis, and molecular biology; modern
neo-Darwinism is a broad umbrella of scientists who disagree about
some questions (such as gradualism versus punctuated equilibrium) but
agree on major concepts. neo-Darwinian theories of evolution
propose mechanisms for: Is
DESIGN defined by DESCENT? Is
EVOLUTION defined by
DESCENT? Is
proof possible in science? Young-Earth
Creationism: |
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Logical
Evaluations of Evolution Critical Thinking about Evolution in Public Education and from a variety of authors, |
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http://www.asa3.org/ASA/education/origins/logic.htm
Copyright © 2002 by Craig Rusbult, all rights reserved