One of the most powerful
argumentative techniques in favor of some truth claim is to assert
that there is some consensus of opinion among scientists that the
claim is correct. But often such assertions are unwarranted. Quite
a few of the times that people claim that there is a scientific
consensus on something, there is no actual majority of scientists who
assert such a thing. Below are six reasons for thinking that quite
a few claims of scientific consensus are exaggerated, and are not
matched by an actual majority opinion of scientists on the matter in
question.
Factor #1: Claims of
Consensus Are Often Made Before a Consensus Is Reached
Let's imagine that there's
some theory that is starting to get traction in the scientific
community. Imagine you are some advocate for the theory, trying to
get even more people to accept it. What is your easiest route to such a
goal? It is to claim that there is a scientific consensus in support
of this theory you support. Many people will meekly fall into line
and accept your theory, as soon as they hear a claim that most
scientists have accepted the theory. The temptation to claim “most
scientists believe this” is so great that people often make such
claims even when no such consensus has been reached.
Factor #2: Most People
Who Claim a Scientific Consensus Offer No Evidence
The great majority of
statements claiming a scientific consensus on something offer no
evidence to back up for such a claim. For every time that someone
claims that most scientists agree on something, and tries to back up
such a claim by referring to some opinion poll or study of scientific
opinion, there must be ten or twenty times that someone claims that
most scientists agree on something without offering any evidence to
back up the claim.
Factor #3: There
Typically Exist No Formal Processes for Identifying the Opinions
of Scientists on Theories
Given
the fact that people
are often claiming that most scientists think such-and-such a thing,
it is rather surprising to consider that there typically exists no systematic
process for having scientists state their opinions on whether
particular theories are true. In the world of science, there is
nothing equivalent to the voting booth. For example, scientists are
not sent annual questionnaires in which they are asked to rate the
likely truth of different theories on a scale of 1 to 10, with 10
being certainty about a particular theory.
So
when people claim that most scientists believe this or most
scientists believe that, and try to back up their claims with some
evidence, they may refer to opinion polls or a survey of the
scientific literature. These are very imperfect measures of opinion,
for reasons discussed below.
Factor #4: People
Often Self-Censor Private Opinions Conflicting With Perceived Norms
In November of 2016 there
was a startling result in the American presidential election. Donald
Trump won a victory in the electoral college, despite losing the
popular vote by millions. This was despite both late election polls
showing him losing by a substantial margin, and also Election Day
exit polls showing him losing in some of the key states he won. A
reasonable idea to explain this is the idea of self-censorship. This
is the idea that when people hold opinions that differ from perceived
norms, they often never publicly state such opinions, and will only
express them in something like a secret ballot. It may be that a
significant percentage of voters planned to vote for Trump, but told
pollsters otherwise, as they regarded their support of Trump as
something that conflicted with perceived norms.
We have no idea how much
self-censorship plays a role in scientific opinion. Many a scientist
may disagree with theories that are supposedly supported by a
majority of scientists. Such scientists may engage in
self-censorship, figuring that it is not a good career move to speak
in opposition to some theory that many other scientists are
supporting. This makes it harder to determine just what the majority
of scientific opinion really is.
An example of self-censorship
Factor #5: It Is Very
Hard to Unravel the Level of Support for a Theory Based on Scientific
Papers
Since scientists have no
formal process for voting on the truth of theories, some people have
attempted to use studies of scientific papers to draw conclusions
about a scientific consensus on some topic. Such attempts can be
problematic.
An example of an analysis
of scientific papers that offers limited insight is this study, which
has been widely although inaccurately summarized as reporting a 97%
consensus about anthropogenic global warming. It is probably correct
that a majority of scientists do believe that mankind is the main
cause of global warming, although the study does not back up the
claim of 97% consensus. For one thing, the study was based only on
abstracts, those short summaries that appear at the top of a
scientific paper. Secondly the study actually reported that 66% of
the abstracts reported no opinion about man-made global warming. The
97% figure was from a second phase that sent a questionnaire to those
who had already stated an opinion in their abstract about whether
humans cause global warming. Of those people, only 14% responded; and
of those 14%, 97% supported anthropogenic global warming either
explicitly or in a weaker implicit sense. It is not correct to
extrapolate from such a fraction of a fraction and make the same 97%
claim about the scientific community in general, particularly given
the dubious business of getting that 97% by lumping together explicit
endorsements of anthropogenic global warming and merely implicit
endorsements that may be more nuanced and ambiguous.
Page 15 of this Pew poll of scientists
indicates that only 89% of them agreed that earth is warming mostly due to human activity, and that only 77% of them agreed that global warming is a
very serious problem. This suggests a consensus about this topic much
less than the 97% figure cited (I agree with the 89% on this topic).
It would also be extremely
problematic for someone to draw conclusions about a scientific
consensus based on an analysis of scientific papers on topics such as
cosmic inflation or string theory. Let us consider a physicist who
has become familiar with the arcane speculative mathematics of string
theory or cosmic inflation theory. Such a physicist learns that he
can make a comfortable living grinding out speculative papers
offering yet another twist on these theories. But suppose this scientist publishes
five papers on such a topic. Does it mean he actually believes the
theory is likely to be true? We cannot tell. It could be that the
physicist is simply interested in the mathematics, and finds that he
can fulfill his yearly quota of scientific papers by writing on the
topic. Such a thing does not tell us whether the scientist believes
such theories to be true.
Factor #6: Opinion
Polls Of Scientists Can be Misleading or Confusing Because of the Way
They Are Phrased
Pros in the political
field know that the way questions are worded can have gigantic
effects on the results. For example, if a question asking about
support for abortion is worded from a pro-choice perspective, it will
get some answer suggesting a very high support for allowing abortion.
The same question worded from a “protect the unborn child”
perspective may show a vastly different level of support for allowing
abortion.
The same principle holds
true in regard to polls of scientists about scientific theories. For
example, a Pew opinion poll asked a question of scientists that
seemed designed to produce the highest level of response: a question
asked whether they agree that “humans and other living things have
evolved over time.” That got a 98% yes response. But “evolved
over time” could mean small-scale stuff, what is known as
microevolution. A scientist believing in small-scale evolution may
answer “Yes” to such a question, even though he doesn't believe
in the origin of species from more primitive species, or does not believe that such a thing is mainly caused by natural
selection.
Very absurdly, the Pew poll question gave respondents a choice between asserting that "Humans and other living things have evolved over time" and "Have existed in their present form since the beginning of time." Such a choice forces anyone believing in a 13-billion-year-old universe to choose the first answer, since there is no option such as "Humans originated for unknown reasons about 100,000 years ago, long after the Big Bang." This is a classic pollster's goof: make it seem like almost everyone believes in choice A by offering a choice between choice A and some choice B that almost no one would accept.
Very absurdly, the Pew poll question gave respondents a choice between asserting that "Humans and other living things have evolved over time" and "Have existed in their present form since the beginning of time." Such a choice forces anyone believing in a 13-billion-year-old universe to choose the first answer, since there is no option such as "Humans originated for unknown reasons about 100,000 years ago, long after the Big Bang." This is a classic pollster's goof: make it seem like almost everyone believes in choice A by offering a choice between choice A and some choice B that almost no one would accept.
What if these questions
were asked:
Is it true that humans
have evolved from ape-like ancestors?
Is it true that humans
have evolved from ape-like ancestors mainly because of Darwinian
natural selection?
These are the questions
Pew should be answering, but it doesn't. On page 28 of this full
report, it does ask the respondent to choose between the choices
shown below:
A poll of scientists (with dubious aspects discussed above and below)
It is interesting that despite constant indoctrination to the contrary, nearly two-thirds of the public reject the claim that humans have evolved over time due to natural processes such as natural selection. It is also interesting here
that about 10% of scientists do not believe that evolution occurs
mainly because of natural processes such as natural selection. The survey was made only of American Association for the Advancement of Science members, a subset of scientists more likely to be "old guard" thinkers conforming to ideological orthodoxy. A full survey of scientists might have yielded a number greater than 10% doubting the "party line" on this topic.
Here we also have a case where there is a large chance of significant self-censorship, as the prevailing academic culture declares deviation from Darwinian orthodoxy as a taboo. The actual percentage of scientists rejecting the Darwinian explanation may be much higher than the 10% indicated in this survey, and could easily be as high as 15% or 20%. The people who responded to the Pew survey were people who responded after being mailed a letter with the AAAS masthead, signed by the head of the AAAS. That must have maximized the peer-pressure "fall in line with the majority" effect. A secret ballot without such a "Big Brother is watching" effect might have produced a very different result.
Here we also have a case where there is a large chance of significant self-censorship, as the prevailing academic culture declares deviation from Darwinian orthodoxy as a taboo. The actual percentage of scientists rejecting the Darwinian explanation may be much higher than the 10% indicated in this survey, and could easily be as high as 15% or 20%. The people who responded to the Pew survey were people who responded after being mailed a letter with the AAAS masthead, signed by the head of the AAAS. That must have maximized the peer-pressure "fall in line with the majority" effect. A secret ballot without such a "Big Brother is watching" effect might have produced a very different result.
But the poll still doesn't
tell whether there is any consensus about natural selection as an
explanation for evolution. The poll asks about “natural processes
such as natural selection,” but does not tell us what percentage of
scientists are satisfied with the "prevailing party line" claim that natural selection and
random mutations can explain the mountainous amounts of biological
complexity we observe. Is that percentage 70%? 60%? Or less than 50%?
We don't know. Although we sometimes hear claims that almost all
scientists believe the idea that Darwinian natural selection explains
the origin of species and biological complexity, we don't have polls
backing up such a claim. We don't know whether this supposed
overwhelming majority is even a 50% majority.
What about fields such as
neuroscience? Is it really true that an overwhelming majority of
neuroscientists believe that the mind is purely a product of the
brain? We don't know, because there is no institutional scientific
process for voting on such a thing.
Conclusion
From
the discussion above, two general conclusions may be drawn:
- When it is claimed that there is a scientific consensus on something, the consensus is often much weaker than is claimed, with a substantial minority rejecting the majority opinion.
- Although some claims of a scientific consensus are warranted, it is often claimed that most scientists agree on some topic, when there is actually no clear evidence that such a majority of opinion exists.
So what are you going to do, when the waters are so muddied in regard to what scientists think? The answer is simple: decide based on facts, logic and evidence, rather than following an “I'll think like most of them think” strategy. Since the insular tribes of academia are often ideological enclaves very much subject to dubious thought customs, inappropriate hero worship, bandwagon effects, sociological influences and groupthink, it's not a good idea to simply follow an “I'll go with the crowd” principle. “Follow the facts” and "follow the logic" are better principles than “follow the crowd.”
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