"97% of scientists agree that climate change is caused by humans - if 97% of scientists told you a plane was going to crash, would you get on it?"

Arguments about the existence of climate change aside - is there a logical fallacy of some sort being employed in the statement above?

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    We should note that 97% of scientists telling you that a plane is going to crash doesn't prove it will, but still makes it a bad idea to get on it. – gnasher729 Oct 23 '14 at 14:13
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    You're getting lots of answers that hem and haw about the validity of the argument because it's a hot political issue. Leaving aside the existence of climate change, as per your question, there is clearly and argument from authority (of scientists) and equivocation (between completely separate fields of science/engineering) in the argument. – Aaron Golden Oct 23 '14 at 19:13
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    97% of what scientists? If the 97% are all, say, anthropologists (whether or not the remaining 3% are as well), I wouldn't consider their opinion of the plane's airworthiness relevant. If they are, instead, metallurgists or aerospace engineers, I'll consider delaying my flight. (I think this is the point alanf makes in his answer as well.) – chepner Oct 23 '14 at 19:19
  • If they were materials scientists or maybe meteorologists who said the plane would crash, sure, I'd consider it. But I'd rather trust the aeronautical engineers on that one. – Joe Oct 23 '14 at 19:26
  • @chepner: the figure is from a poll of scientists - the 97% is of currently active climatologists. – naught101 Oct 24 '14 at 0:58
up vote 6 down vote accepted

We could quite reasonably say that there is a logical fallacy of "argument from authority". However, we should then also say that "argument from non-authority" is probably a much worse fallacy (assuming that something must be true because some minor celebrity having not a clue of the subject says it's true, which happens often enough).

And the logical fallacy doesn't make it wrong. It's not proven, but most things in life are not proven, and in the absence of proof we cope by using probabilities. If 97% of scientists agree on something that is within their area of expertise, then the probability that it is right is quite high.

If you insist to act only on things that are 100% proven, then consider that "climate change is not created by humans" is only supported by 3% of climate scientists, and therefore much less proven than the opposite statement.

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    "The logical fallacy doesn't make it wrong." Absolutely true. A logically flawed argument of itself tells us nothing about the truth or falsehood of a statement. You can't judge the validity of a proposition by the weakest arguments made for it; you must judge by the strongest. Of course if the ONLY arguments made to support an idea are flawed, then we'd have to say that the idea is weak. – Jay Oct 23 '14 at 19:22
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    I don't necessarily consider argument-from-authority to be a fallacy. Sure, it's not the strongest argument you could make, but in this case we're asking people who have far more experience and knowledge than us. Argument-from-authority just says we should respect that.¶ I also am not sure this is exactly argument-from-authority, though. This is more argument-from-experience or argument-from-superior-knowledge-that-would-take-too-long-for-me-to-explain-to-you-fully. – imallett Oct 23 '14 at 19:54
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    It's more obvious if you consider that health scientists employed by tobacco companies know ten times better than we do whether smoking damages your health or not, and they say it doesn't - the problem here is that I don't trust them. So you need authority and reasonable trust. Or authority and verification. – gnasher729 Oct 23 '14 at 20:16
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    @GraphicsResearch See my comment on the question for why this is not really an argument from authority. – Pont Oct 24 '14 at 13:14
  • May not be a considered factor in this question as the OP has posted it, but in the actual poll, it's worth noting that it was 97% of the papers taking a position. The amount of papers taking a position were much less than the total number of papers on the topic. See the question on skeptics for more. Just realized @Pont is pointing out a similar argument – DoubleDouble Oct 24 '14 at 17:23

Suppose that a person advises you to do something, such as accept some idea or other. Whether you should do it depends on whether the person in question can refute objections to the course of action he is advising.

The fact that somebody happens to have called the person in question a scientist doesn't change that.

Some people seem to think that it makes a difference, but it doesn't. Scientific knowledge is created by conjecture and criticism, see "Realism and the Aim of Science" Chapter I by Karl Popper.

The idea that you should drop your standards of criticism when somebody says the word "scientist" is anti-rational and anti-scientific. That is, adopting or advocating such an absence of standards is a threat to science and rationality.

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    So, we should treat all opinions as if they were equally useful? The label "scientist" doesn't just tell us the job that a person does. It also indicates that they have some level of experience and expertise in their area of study. – naught101 Oct 24 '14 at 1:02
  • @naught101 Alan didn't say you should treat all opinions equally - that's a notion of Greek philosophy, not science. He just said that you shouldn't turn off your "criticism circuits" just because you heard that the claim was presented by a scientist. The prevalence of this fallacy is well seen on how many people accept claims by scientists out of their fields of expertise. Not to mention that this also means the general public tends to ignore claims made by engineers, who should be trusted way more than people who abstract on spherical cows, so to speak :D – Luaan Oct 24 '14 at 8:29
  • @naught101: No. The label "scientist" tells you precisely one thing, that somebody has called that person a scientist. Some people who are labelled in this manner are not scientists, e.g. - creation scientists. Now, if somebody who has good ideas about science identifies somebody as a scientist I may be inclined to pay attention to the scientist's opinions about matters of fact of which they have knowledge. That is, I will read what they have written about the issue, take it seriously as an explanation and treat it accordingly: I will either accept or reject it. – alanf Oct 24 '14 at 8:41
  • @naught101: You say that the scientists have experience. Merely having long acquaintance with some issue does not make a person's opinion about it correct. What matters is whether that experience has been used to come up with ideas that can be tested or criticised, and whether problems with their ideas have been spotted and removed. Long experience of having a wrong idea counts for nothing. – alanf Oct 24 '14 at 8:48

To be fair, the question is obviously intended rhetorically and rhetoric is in part about persuading people to make leaps of faith. From that perspective, this argument is probably a good one -- but if you wanted to answer it with rhetoric of your own from an apparently more sceptical position:

is there a logical fallacy of some sort being employed in the statement above?

There might be if the point is to not get on the plane, because this would be a classic fallacious argument from authority:

  1. Scientists are (valid) authorities WRT science; but note this is really excessively general. In this instance presumably what we mean is, climate scientists are experts on climate science.
  2. You should trust such scientists when 97% of them agree.
  3. If 97% of them say a plane is unsafe, then it must be so.

Number 3 is the genuine non-sequitur but it rides a bit on 2 of course.

However, the statement isn't about the plane, and there are a number of other "bad faith" interpretations in the above critique making it an intentional misinterpretation ("playing semantics"). In other words, this argument is unlikely to be taken seriously by anyone.

A reasonable, literate, and disinterested observer would probably say what was really meant was (i.e., a "good faith" interpretation):

Aerospace engineers are recognized experts on planes. If 97% of aerospace engineers said not to get on a plane, you would not get on the plane. Climate scientists are the recognized experts on climate, so when 97% of them say something about the climate, why don't you believe them?

Fleshed out like this, though, we begin to see the outlines of the problem alanf identified, namely that this might be a dubious argument from authority. It might even be considered fallacious in the same sense as the first example here albeit in a more round about way. The expertise of the aerospace engineers is more certain because aerospace engineers design planes, whereas climate scientists do not design climates, they just analyse them. Because of this, aerospace engineers have much more experience with trial and error, etc., and if 97% of them said a plane was unsafe, they're probably right.

The analogy to climate and climate scientists is a bit weak; I would call it dubious and not fallacious. The point is still clear, so again, as rhetoric, this works, and it is hard to counter in that sense.

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    Sure, I took it for granted that the intent of the analogy was "97% of aerospace scientists". But even at that, I'd say "that depends". If, say, this is a new experimental aircraft, it may be that the designer is a genius, and 97% of aerospace scientists are wrong because they are stuck in old ways of thinking. And who conducted this poll? If Foobar Airlines announced that 97% of scientists agree that Plugh Airlines planes are unsafe, I wouldn't accept that uncritically. Etc. That's why the argument from authority is weak: there are a million reasons why the experts could be wrong. – Jay Oct 23 '14 at 19:27

I do not see this way of presenting things as a logical fallacy. This short two sentence summary is not a formal proof, and it's not intended to be. It's intent is to get you to agree to one of the premises of a subsequent argument: that in cases where there is scientific consensus you can/should use that information in guiding your decisions.

That implication is not directly argued for or justified in any manner, and thus there are various ways to diffuse it; alanf has already presented one. Another would be that scientific consensus about climate change is a different beast than scientific consensus about whether a plane is flightworthy, and thus even if you accept the second sentence, it need not affect your thoughts w.r.t. climate change. You can also pick apart features of "which scientists" and "where did this 97% number come from" etc.

Merely presenting things in a manner that seems to lead to an obvious conclusion does not make the presentation fallacious.

This is the logical fallacy known as "recourse to authority". It says that you should believe something, not because the writer has presented any actual evidence to back it up, but simply because some expert says it is so.

If the expert believes that something is true because he has evidence to back up his assertion, then he should present the evidence. In that case you will be convinced by the evidence (assuming that the evidence is, in fact, convincing), and not by the fact that an expert said so.

If the expert does not have any evidence, then his opinion is no more well-informed than any random person's off the street.

Either way, you should be convinced by the evidence, not the fact that an expert said so.

In recent years I've heard some try to justify this sort of flawed argument by renaming the fallacy, "recourse to INAPPROPRIATE authority", and claiming that if the authority has the right credentials, that you should believe them. A little thought will show that this is a hollow distinction. OF COURSE anyone who says that you should believe something because an expert said so will claim that the expert's credentials make him authoritative. Who would say, "Bill Smith says that X is true. Of course Bill Smith knows absolutely nothing about the subject, but you should just believe him anyway." They're always going to say that Bill Smith is an expert on the subject. People who make this argument are trying to divert you into an argument about Bill Smith's credentials instead of the subject at hand. But even if Bill Smith has a master's degree in a relevant field and has worked in this field for 30 years, if he has no evidence to back up his claims and is just tossing out unsubstantiated opinion, what difference does his degree and experience make?

I'm not going to get into the debate about global warming per se here, that's a whole 'nother subject. But to embrace the analogy:

If someone told me that 97% of scientists say this plane is going to crash, I would likely ask who this person is who is telling me and who the 97% of scientists are.

How did he get this statistic? Did he really poll an unbiased collection of relevant scientists? It's quite possible that the statistic is from a biased poll, or that he just made it up. On controversial, politically charged subjects, that's not uncommon.

What is his definition of a "scientist"? Everyone with a PhD in science? But what would someone with a degree in biology or astronomy know about the reliability of an airplane? Their opinion is unlikely to be any more informed than any random person off the street. They're probably just repeating what they've heard from others.

Often when you hear statements that some large majority of experts agree that X, it turns out that they are defining X to only include people who agree with them. Like, "We asked the scientists who work for Foobar Airlines, and 97% of them agreed that planes from Whatsit Airlines are dangerous and will probably crash." Or, "We asked scientists who really know about the dangers of air travel -- that is, the scientists who are members of the Man Will Never Fly Society -- and 97% agreed, etc."

Experts are human beings, too. They can be biased by their political or social beliefs. A scientist who makes his living studying X is unlikely to say that X is totally bogus. And scientists who have no specific knowledge of the subject in question can fall into the "everybody knows that ..." trap just as easily as the general public.

For example, a number of years ago the president at the time called a conference of economists to evaluate his economic plan. And I saw many stories in the news about how all the economists who attended the conference agreed that the president's plan was basically a good idea, the only question was whether it went far enough. Well, duh. They said that like that proved something. But surely he didn't invite economists who he knew would say he was going in the wrong direction.

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    Not all arguments from authority are fallacious, but an argument from authority can be fallacious; generally the later is when the realm of authority is inappropriately extended ("Cops stand to know a lot about fitness."). This is by no means a "recent re-interpretation" either, that's what it has always meant. You've implicitly indulged the inductive fallacy (note: induction is not always fallacious either): "These apples are green, therefore all apples are green". – selfConceivedAsEvil Oct 23 '14 at 13:59
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    BTW I might point out that nowhere in my post did I use an argument from induction. I did not say, "In cases X and Y it turned out that the experts were wrong, therefore experts are always wrong." Quite the contrary, I used a deductive argument, questioning what the statement of an expert proves in the absence of evidence. Your argument is an example of a sort of straw man, refuting an argument I didn't make and claiming that that somehow disproves the argument that I did make. :-) – Jay Oct 23 '14 at 14:20
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    I'll agree an argument from authority is weaker than, e.g., an argument from pure logic, etc., but it is not no argument at all. People take weather forecasts seriously even if they are sometimes wrong, and a weather forecast is mostly an argument from authority with minor bits of empirical evidence thrown in. What I'm objecting to is your first sentence: This is the logical fallacy known as "recourse to authority". Recourse to authority is not a fallacy, but it may be fallacious. – selfConceivedAsEvil Oct 23 '14 at 14:21
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    Besides, you must accept that the recourse to authority is a logical fallacy, because Aristotle described it as a logical fallacy, and Aristotle is the greatest philosopher and logistician in history. :-) – Jay Oct 23 '14 at 14:21
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    Presuming the expert isn't lying, it's proof of the fact the expert believes it, that's all. As you say, it can't be used to contradict empirical evidence. But it would be impossible to live a normal life if you rejected all arguments from authority as fallacious: you would have to become an expert on everything that concerns you, and on top of that do an absurd amount of work applying your expertise in investigation of everything. – selfConceivedAsEvil Oct 23 '14 at 14:35

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