[Editor's Note:
This article was adapted from a 5-part series originally published on
Evolution News & Views. The original 5 parts can be seen here: Part 1, Part 2, Part 3, Part 4, Part 5.]
Introduction
Many members of the general public who are skeptics of Darwinian
evolution are intelligent people with a decent understanding of some of
the scientific weaknesses with neo-Darwinian evolution. In fact, a
recent article in The Scientist
suggests that, "public discontent with classical evolution as an
inclusive theory stems parly from an intuitive appreciation of its
limits." (Eric Smith, "Before Darwin," The Scientist, June
2008:32-38.) But in this highly nuanced debate, such Darwin-skeptics
must avoid semantic land mines if they are to accurately, clearly, and
effectively communicate their views. I have often seen that some people
who oppose neo-Darwinian evolution are fond of calling evolution "only a
theory" or "just a theory, but not a fact." After using such a phrase,
they are immediately scolded by Darwinists, who tell them that "a
theory" is a "well-substantiated scientific explanation of some aspect
of the natural world" and that evolution should be considered "both fact
and theory."
Ken Miller just wrote a book titled, "Only a theory," basically opposing people who use such an argument. Similarly, an opinion article recently condescended:One
of the greatest misconceptions about evolution is embedded in the
misuse of the word 'theory' in its application to science. The common
antecedents that result in this misuse of the word are manifested in
either genuine ignorance, or disguised ignorance. People are either
genuinely mistaken of the word's intent, or they are well aware of the
word's scientific definition, but still use the nonscientific definition
in an effort to spawn doubt. … Evolution, because it's a theory, is a
higher form of knowledge than a fact.Similarly, the NCSE's Glenn Branch recently co-wrote an article
taking the condescending approach: it labeled those who use the
"evolution is 'just a theory' line as being "pejorative" and favorably
cited a Darwinist who scolded, "To claim that evolution is ‘just a
theory’ is to reveal both a profound ignorance of modern biological
knowledge and a deep misunderstanding of the basic nature of science."
Question 1: Are Darwinists correct to define
"theory" as "a well-substantiated scientific explanation of some aspect
of the natural world" or "a comprehensive explanation of some aspect of
nature that is supported by a vast body of evidence"?
According to the 1998 edition of the U.S. National Academy of Sciences' (NAS) Science and Creationism: A View from the National Academy of Sciences,
a theory is "a well-substantiated explanation of some aspect of the
natural world that can incorporate facts, laws, and tested hypotheses."
In 2008, the NAS released a new edition, Science, Evolution, and Creationism,
stating that a theory is "a comprehensive explanation of some aspect of
nature that is supported by a vast body of evidence." Darwinists
routinely invoke these and other similar definitions of "theory" when
scolding Darwin-skeptics for calling evolution "just a theory, not a
fact." Are Darwinists correct to define "theory" in this fashion? The
answer to this question is both yes and no.
"Theory" can have multiple definitions. When I look up "theory" in my
1996 edition of Webster's Encyclopedic Unabridged Dictionary of the
English Language (WEUDEL), the word “theory” has 7 or 8 different
entries: 1. a coherent group of general propositions used as
principles of explanation for a class of phenomena: Einstein's theory of
relativity.
2. a proposed explanation whose status is still conjectural, in contrast
to well-established propositions that are regarded as reporting matters
of actual fact.
3. Math. a body of principles, theorems, or the like, belonging to one subject: number theory.
4. the branch of a science or art that deals with its principles or methods, as distinguished from its practice: music theory.
5. a particular conception or view of something to be done or of the method of doing it; a system of rules or principles.
6. contemplation or speculation.
7. guess or conjecture. According to entry #2, "theory" can mean
"a proposed explanation whose status is still conjectural, in contrast
to well-established propositions that are regarded as reporting matters
of actual fact." Similarly, entries #6 and #7 define "theory" as
"contemplation or speculation" or "guess or conjecture." We’ll say
these comprise the soft definition of theory and represent the
definitions that the average person has in mind when they say,
"evolution is just a theory, not fact."
The upshot of the soft definition of theory is that Darwinists
who imply that the term "theory" can never mean that "conjecture or
guess" are in fact wrong, because "theory" can in fact mean conjecture
or guess. On the other hand, if you’re a Darwin-skeptic who thinks that
"theory" necessarily means "conjecture" or a "guess" and can never mean
a verified scientific explanation, then you are wrong: After listing
these entries, my 1996 edition of WEUDEL elaborates on proper usage of
the word "theory" within the scientific community:1. THEORY,
HYPOTHESIS are used in non-technical contexts to mean untested idea or
opinion. The THEORY in technical use is a more or less verified or
established explanation accounting for known facts or phenomena: the
theory of relativity. A hypothesis is a conjecture put forth as a
possible explanation of phenomena or relations, which serve as a basis
of argument or experimentation to reach the truth: This idea is only a
hypothesis.Within technical scientific discussions, the term
"theory" typically is understood to mean "a more or less verified or
established explanation." We’ll call this the hard definition of theory. But is this hard definition of theory the only way that scientists use the word "theory"?
When a Darwin-skeptic says "evolution is a theory, not a fact,"
Darwinists often pounce and assert that the colloquial or "pejorative"
(Glenn Branch's label) usage of "theory" can mean "conjecture" or
"guess," but scientists never use the word "theory" to mean
conjecture or guess. For example, Branch favorably quotes Ken Miller's
2007 edition of the textbook Biology, implying that there is a
united front and complete conformity within the scientific community
regarding proper usage of the word "theory": "In science, the word
theory applies to a well-tested explanation that unifies a broad range
of observations." Such Darwinist claims of unanimity within the
scientific community are also questionable.
While scientists do typically imply the "hard" definition when using the
word "theory," they don't always use it in that sense. If scientists
always meant the "hard" definition of "theory," then scientists would
virtually never use the phrase "new theory" because an idea does not
attain the status of a theory until it becomes well-established and
verified, withstanding many tests until it is no longer "a proposed
explanation whose status is still conjectural." Yet a quick search of
PubMed for the phrase "new theory" reveals dozens and dozens of hits
from the technical scientific literature where scientists offered "a
proposed explanation whose status is still conjectural" but called that
explanation a theory.
Three recent examples of such usage of "new theory," where theory represented an unverified idea, will suffice.
In the April, 2008 issue of the journal Medical Hypotheses,
editor-in-chief Bruce G. Charlton uses the phrase "new theory" multiple
times. The meaning implied by the term "theory" in this case was a
proposed explanation whose status is still conjectural, in contrast to
well-established propositions that are regarded as reporting matters of
actual fact. As Charlton observes:An old joke about the
response to revolutionary new scientific theories states that there are
three phases on the road to acceptance: 1. The theory is not true; 2.
The theory is true, but it is unimportant; 3. The theory is true, and it
is important – but we knew it all along. ... Theory for scientists is
like water for fish: the invisible medium in which they swim.
(Bruce G. Charlton, "False, trivial, obvious: Why new and revolutionary theories are typically disrespected," Medical Hypotheses, Vol. 71:1-3 (2008).)Charlton
goes on to say, "When a new theory is revolutionary, then it is
perceived as an observation which is incompatible with the old theory.
From this perspective either the new theory must be rejected, or else
the old theory abandoned." Clearly Charlton uses the word "theory" as
if it can, in some circumstances, mean a new idea that has not yet
undergone widespread testing and verification, and may not have
experienced widespread acceptance.
As a second example, a recent sociology paper from Archives of Suicide Research
states, "Although the study has offered some support for the new
theory, future research with more rigorous quantitative data needs to be
conducted to further test the theory on a more comprehensive level."
(J. Zhang, D. Lester, "Psychological Tensions Found in Suicide Notes: A Test for the Strain Theory of Suicide," Archives of Suicide Research,
Vol. 12(1):67-73 (2008).) Clearly this study uses the word "theory" to
describe a new idea that has not yet been fully verified nor accepted.
Finally, even within the context of evolutionary biology, theory can
mean a new idea that does not yet have widespread verification or
universal acceptance. A recent article in Current Biology entitled "Social Evolution: The Decline and Fall of Genetic Kin Recognition,"
by Andy Gardner and Stuart A. West of the Institute of Evolutionary
Biology, University of Edinburgh, contains a subheading which asserts,
"New theory confirms that genetic kin recognition is inherently
unstable, explaining its rarity." Yet the article goes on to describe a
vigorous scientific debate between evolutionary biologists about whether
kin selection is a genetically viable explanation to account for the
evolutionary origin of altruism and cooperation. According to the
article, a new study concludes that "there is relatively poor empirical
support for this mechanism in nature" because "[a] new theoretical study
of genetic kin recognition … reveals that, left to its own evolutionary
devices, this mechanism will drive itself to ruin." But other leaders
in that field disagree, implying that this theory is not "a
well-substantiated scientific explanation of some aspect of the natural
world" or "a comprehensive explanation of some aspect of nature that is
supported by a vast body of evidence."
There are many other examples from the technical literature where theory
is used in a similar sense, and it does not mean "a more or less
verified or established explanation." It should be clear that
scientists sometimes DO use the term "theory" to refer to a new idea
that has not yet undergone extensive testing and is simply "a proposed
explanation whose status is still conjectural."
In closing, we must return to the question, Are Darwinists correct to
define "theory" as "a well-substantiated scientific explanation of some
aspect of the natural world" or "a comprehensive explanation of some
aspect of nature that is supported by a vast body of evidence"? The
answer is yes, but they are not entitled to claim that such a hard
definition is the exclusively acceptable usage of theory both for
scientists and non-scientists. Darwinists are wrong to imply that
scientists always necessarily use the hard definition of theory, because
even scientists occasionally use theory as if it means new idea, or a
"a proposed explanation whose status is still conjectural."
The problem underlying debates over the proper usage of theory is that
the term can have multiple definitions, even among scientists, ranging
from "a proposed explanation whose status is still conjectural, in
contrast to well-established propositions" to "a more or less verified
or established explanation." But the upshot is this: Because the
term "theory" can mean "a more or less verified or established
explanation," it is inappropriate for a Darwin skeptic who is trying to
communicate doubts about Darwin to use the "evolution is a theory, not a
fact" line, because it ignores the truth that in many venues, theory
does indeed mean, as WEUDEL explains, "a more or less verified or
established explanation."
Question 2. Under such a strong definition of "theory," does evolution qualify as a "theory"?
It seems clear that scientists can use the word "theory" to mean
"conjecture," but it is also fair to say that typical circumstances,
when scientists say "theory," they mean the hard usage of the
term: "a more or less verified or established explanation." This thus
leads to the question, under such a strong definition of the term, does evolution qualify as a theory?
Assuming that we are using the hard definition of theory, different
people will give different answers to that question. Under such an
understanding of the term, if we define theory as "a more or less
verified or established explanation," then theory is in the eye of the
beholder. Darwin-skeptics will not agree that neo-Darwinian evolution
is "a more or less verified or established explanation." But Darwinists
will agree. So the question over whether neo-Darwinian evolution
should be called a "theory" is not the core question of this debate. A
better question would be: "Is neo-Darwinian evolution ‘a more or less
verified or established explanation’?"
Darwinists have the right to believe that neo-Darwinian is a verified and established explanation--i.e. that it meets the hard
definition of theory. But they do not have the right to insist that
Darwin-skeptics must call evolution a "theory," so defined. While
Darwinists are correct that the technical definition of "theory" means a
well-established and verified explanation, they should not insist that
evolution can never be called "just a theory." When they do this, they
are actually imposing onto the debate their conclusion that evolution
must be considered by all to be a verified and established explanation.
Were they to tolerantly allow Darwin-skeptics to dissent from the
orthodox neo-Darwinian position, Darwinists would not insist that
Darwin-skeptics entirely abandon the phrase "evolution is just a
theory."
However, given that the technical, scientific, hard definition of
theory does typically mean a well-established and verified explanation,
then it is best if Darwin-skeptics take the high road and avoid calling
neo-Darwinian evolution "just a theory." And as we shall see in the
next section, the question "is evolution a 'more or less verified or established explanation'?" is also a complex question, for it can also depend on the definition of "evolution."
Question 3. Is it correct to call evolution a "fact"?
A new article in Current Biology
about Darwin Day celebrations quoted Johnjoe McFadden from the
University of Surrey stating that "evolution is no longer just a theory.
It is as much a fact as gravity or erosion. Scientists have measured
evolutionary changes in scores of organisms." The leading 20th century
evolutionary biologist Ernst Mayr quite dogmatically (and wrongly) claimed
that, "No educated person any longer questions the validity of the
so-called theory of evolution, which we now know to be a simple fact."
Similarly, according to the ardently pro-Darwin U.S. National Academy of
Sciences (NAS), evolution is a "fact": Is Evolution a Theory or a
Fact? It is both. But that answer requires looking more deeply at the
meanings of the words "theory" and "fact."
(U.S. National Academy of Sciences, Science, Evolution, and Creationism, pg. 11 (National Academy Press, 2008).)What
these Darwinist authors miss is that the legitimacy of calling
evolution a "fact" depends on the meaning of the word "evolution."
The debate over evolution can be confusing because equivocation has
crept into the discussion. Some people use evolution to refer to
something as simple as small changes in the sizes of birds’ beaks.
Others use the same word to mean something much more far-reaching. Used
the first way, the term "evolution" isn’t controversial at all; used the
latter way, it’s hotly debated. Used equivocally, evolution is too
imprecise to be useful in a scientific discussion. Darwin’s theory is
not a single idea. Instead, it is made up of several related ideas, each
supported by specific arguments:***
The failure of developmental biology to explain why vertebrate embryos diverge from the beginning of development. (see "Evolving views of embryology" for a discussion).
But how does one simply communicate such viewpoints without getting into
semantic trouble? I don’t recommend one-liner sound-byte arguments
against evolution because they don’t communicate anything about the
content of the scientific deficiencies of neo-Darwinism. Here's why:
When someone says "evolution is just a theory," it sounds like the
speaker cannot cite actual scientific evidence against evolution, and
that the only objection the speaker can muster is based upon appealing
to postmodern rhetoric which asserts that we really can’t know if
anything is true. The truth is that science is capable of studying the
validity of historical scientific theories such as neo-Darwinism, but
the "evolution is just a theory" line makes it sound like the speaker is
not interested in studying or discussing that evidence. In the debate
over evolution, discussions of evidence are what matter most. As stated
previously, calling something a theory doesn't necessarily tell you
about the state of the evidence. The best way to express dissent from
evolution is to actually discuss its failure to explain the scientific
evidence.
The "evolution is just a theory" line can come off as if the speaker
really thinks "evolution is just a guess, so I don't have to believe it
if I don't want to." In fact, neo-Darwinian evolution as a whole is not
merely a guess and most Darwinian scientists will provide reasons why
they think it is the best explanation for the diversification of life.
If you’re like me, and you think that neo-Darwinian evolution has
scientific problems, then you should be able to provide reasons beyond
stating "it's just a theory." As noted above, the best strategy is for
you to be prepared to give a few specific scientific reasons why you
question Darwinian evolution.
But if you really must use short, one-liner sound-bytes to describe
doubts about neo-Darwinian evolution, here is my advice: As we learned
in earlier, the technical definitions of theory do indeed mean "a more
or less verified or established explanation," whereas a hypothesis has
the meaning of "a conjecture put forth as a possible explanation." In
this sense, when evolution is defined to include both universal common
descent and a driving force of natural selection acting upon random
mutation to produce the complexity of life (i.e. neo-Darwinian
evolution), for Darwin-skeptics like me, such evolution is not a theory,
nor is it fact. It is "just a hypothesis."
But as I noted above, it’s best to give more information than one-liner
sound-bytes. So I don't recommend that Darwin-skeptics go around saying
"evolution is just a hypothesis," even though such a phrase would
more-accurately use the technical definitions of "theory" and
"hypothesis." What follows is a slightly longer description of what one
might say to communicate doubts about neo-Darwinism while avoiding
semantic mistakes and communicating more than mere soundbyte arguments:When
evolution is defined as mere change over time within species, no one
disputes that such evolution is a fact. But neo-Darwinian evolution --
the great claim that unguided natural selection acting upon random
mutations is the driving force that produced the complexity of life --
has many scientific problems because such random and unguided processes
do not build new complex biological features. According to the
technical definitions of "theory," "fact," and "hypothesis," such
neo-Darwinian evolution is neither theory nor fact. It’s just a
hypothesis."Closing Thoughts
In the end, my final advice for everyone is this: Whether you think
"evolution" is "fact," "theory," or "hypothesis," or some combination
thereof, it’s important to use all of these terms carefully and if
possible, define them when you use them. It’s also important to have
patience with those who may unwittingly misuse these terms, for each of
these terms can have multiple meanings, allowing ample opportunities for
confusion and miscommunication in this highly-charged debate.
Evolution #1: First, evolution can mean that the life forms we see
today are different than the life forms that existed in the distant
past. Evolution as "change over time" can also refer to minor changes in
features of individual species -- changes which take place over a short
amount of time. We can observe this type of evolution going on in the
present and even skeptics of Darwin’s theory agree that this type of
"change over time" takes place. Evolution in this sense is "fact."
However, it is invariably the case that when Darwinists cite some
present-day observations of change within a species, they will be
small-scale changes that are not easily extrapolated to explain how
complex biological features arose.
Evolution #2: Some scientists associate the word "evolution"
with the idea that all the organisms we see today are descended from a
single common ancestor somewhere in the distant past. This claim became
known as the Theory of Universal Common Descent. This theory paints a
picture of the history of life on earth as one great branching tree.
While this meaning of evolution is not necessarily incompatible with
intelligent design, there are many scientific skeptics of evolution who
are skeptical of Universal Common Descent.
Evolution #3: Finally, some people use the term "evolution" to
refer to a cause or mechanism of change, the biological process Darwin
thought was responsible for the branching pattern. Darwin argued that
unguided natural selection had the power to produce fundamentally new
forms of life. Together, the ideas of Universal Common Descent and
natural selection form the core of Darwinian evolutionary theory.
"Neo-Darwinian" evolution combines our knowledge of DNA and genetics to
claim that random mutations in DNA provide the variation upon which
natural selection acts in a completely unguided fashion. It is this
form of evolution that is the most controversial meaning of evolution.
So is evolution a fact? If by "evolution" one simply means "evolution
#1," i.e. small-scale change over time within a species, then evolution
is indeed a fact. No one disputes this kind of "evolution." Thus when
Johnjoe McFadden states that "[s]cientists have measured evolutionary
changes in scores of organisms" and therefore evolution "is as much a
fact as gravity or erosion," he is stating the obvious because he is
simply referring to evolution #1.
But Dr. McFadden is pulling a bait-and-switch: he is using relatively
trivial examples of evolution #1 to bolster more controversial
definitions of "evolution." Thus if by "evolution" one means universal
common descent (evolution #2), or neo-Darwinian evolution (evolution
#3), where the primary adaptive force building the complexity of life is
unguided natural selection acting upon random mutations, then many
scientists would argue that such "evolution" most certainly is not a fact.
A Closer Look at the NAS’ Mistake
Finally, consider how the NAS defines evolution as a fact:In
science, a "fact" typically refers to an observation, measurement, or
other form of evidence that can be expected to occur the same way under
similar circumstances. However, scientists also use the term "fact" to
refer to a scientific explanation that has been tested and confirmed so
many times that there is no longer a compelling reason to keep testing
it or looking for additional examples. In that respect, the past and
continuing occurrence of evolution is a scientific fact. Because the
evidence supporting it is so strong, scientists no longer question
whether biological evolution has occurred and is continuing to occur.
Instead, they investigate the mechanisms of evolution, how rapidly
evolution can take place, and related questions.
(U.S. National Academy of Sciences, Science, Evolution, and Creationism, pg. 11 (National Academy Press, 2008).)I
won’t dispute the NAS's definition of fact, but it’s clear that unless
by "evolution" they mean evolution #1, then there are many scientists
who will disagree with their claim that evolution is a fact. However,
the NAS DID define evolution as evolution #3, i.e. being driven by natural selection acting upon mutation-caused variation:In
the century and a half since Darwin, scientists have uncovered
exquisite details about many of the mechanisms that underlie biological
variation, inheritance, and natural selection, and they have shown how
these mechanisms lead to biological change over time. Because of this
immense body of evidence, scientists treat the occurrence of evolution
as one of the most securely established of scientific facts. … The
atomic structure of matter, the genetic basis of heredity, the
circulation of blood, gravitation and planetary motion, and the process
of biological evolution by natural selection are just a few examples of a
very large number of scientific explanations that have been
overwhelmingly substantiated.
(U.S. National Academy of Sciences, Science, Evolution, and Creationism, pg. xiii, 12 (National Academy Press, 2008).)The
NAS is wrong. Since the NAS defines "evolution" as full-blown
neo-Darwinian evolution, there are many scientists who will not agree
that it is a fact.
Question 4. Is it best for Darwin skeptics to call evolution "just a theory, not a fact"?
In short, no. Having taken over a dozen courses covering evolutionary
biology at both the undergraduate and graduate levels, I’m a scientific
skeptic of neo-Darwinism. But I’ve long opposed using such a rhetorical
line of "evolution is just a theory, not a fact" to oppose evolution
because it gets you caught up in a semantic debate over the proper
definition of fact and theory, and communicates very little about the
most important component of this debate -- the scientific evidence.
(For an early example of my writings on this topic, see my "Response to the ACLU ID FAQ.")
I’ll start with criticism of people on my own side of this debate by
offering four reasons why I oppose using the "evolution is just a
theory, not a fact" line:
1. The statement "evolution is just a theory, not a fact," hopes to
convey some kind of skepticism regarding evolution, but it fails to
adequately define the term. As we learned in Question 3, no one doubts
evolution when it is defined as "populations of living organisms change
over time." Evolution so-defined is an unquestionable fact. But when
evolution is defined as "natural selection acting on random mutation
serves as the primary driving force that built the complexity of life"
or even "all species share a universal common ancestor" (collectively
called "neo-Darwinian evolution") then you’ve traipsed into more
controversial definitions of evolution.
2. The "evolution is just a theory" line is simply not a good way of
expressing skepticism about neo-Darwinian evolution because it assumes
that a theory is something which necessarily lacks evidentiary support.
As we learned in Question 1, the problem with this phrase is that the
word "theory" can indeed mean a scientific idea that is well-backed by large amounts of scientific evidence.
3. When someone says "evolution is just a theory," it sounds like the
speaker cannot cite actual scientific evidence against evolution, and
that the only objection the speaker can muster is based upon appealing
to postmodern rhetoric which asserts that we really can’t know if
anything is true. The truth is that science is capable of studying the
validity of historical scientific theories such as neo-Darwinism, but
the "evolution is just a theory" line makes it sound like the speaker is
not interested in studying or discussing that evidence. In the debate
over evolution, discussions of evidence are what matter most. As stated
previously, calling something a theory doesn't necessarily tell you
about the state of the evidence. The best way to express dissent from
evolution is to actually discuss its failure to explain the scientific
evidence.
4. The "evolution is just a theory" line can come off as if the speaker
really thinks "evolution is just a guess so I don't have to believe it
if I don't want to." In fact, neo-Darwinian evolution as a whole is not
merely a guess, and most Darwinian scientists will provide reasons why
they think it is the best explanation for the diversification of life.
If you’re like me, and you think that neo-Darwinian evolution has
scientific problems, then you should be able to provide reasons why
you're a skeptic beyond stating "it's just a theory." As noted above,
the best strategy is for you to be prepared to give a few specific
scientific reasons why you question Darwinian evolution.
So if we shouldn’t call evolution "just a theory, not a fact" then how
should us Darwin-skeptics refer to evolution? Theory? Fact?
Hypothesis? Something else? I’ll explore this question in the final
section of this article.
Question 5. All I wanted to say is that I’m a
scientific skeptic of neo-Darwinism. How can I convey such skepticism
without stepping on a semantic land mine and getting scolded by
Darwinists?
Great scientific claims must be backed by great scientific evidence.
When most people claim that "evolution is just a theory, not a fact,"
what they really mean is that there is not convincing scientific
evidence to justify the great claim that all life is related through
universal common ancestry and that it evolved via an process of unguided
natural selection acting upon random mutation. Doubts about
neo-Darwinian evolution might stem from:
The failure of evolutionary biology to provide detailed
evolutionary explanations for the origin of complex biochemical features
(see "Opening Darwin's black box" for a brief discussion);