In debates with climate change deniers and creationists, it is often claimed that consensus of scientists is not enough to establish a position beyond dispute. Examples of the problem with consensus are geocentrism, species saltation, ambiogenesis, eugenics, racists theories, etc. These were all theories believed by a large majority of scientists at the time, that were overturned by a few scientists, and often did not become widespread until long after their introduction.

So, is this a fair claim by deniers and creationists, that scientific consensus by itself is not a good standard for considering a position beyond dispute?

  • $\begingroup$ The question itself does not seem to be about the history of science or mathematics. Although historical examples might be given as evidence, the question seems to be about the current state of science and not about the use of phrenology to identify criminal types or scientific racism, etc. $\endgroup$ – Michael E2 Jan 4 '17 at 1:00
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    $\begingroup$ @MichaelE2: The question seems to me to be clearly about the history of science. It just happens to have a topical motivation. $\endgroup$ – Ben Crowell Jan 4 '17 at 1:06
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    $\begingroup$ A question with "ever" in it ... the answer is of course "yes". $\endgroup$ – Gerald Edgar Jan 4 '17 at 15:21
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    $\begingroup$ No genuine scientist would ever claim that a scientific hypothesis is "beyond dispute". That would just be silly, since a fundamental principle of science is that results are always open to revision. Where the deniers etc. go wrong is in their insistence on absolute certainty- itself a non-scientific, essentially religious notion. $\endgroup$ – mobileink Jan 10 '17 at 21:03

There are all kinds of scientific claims, and I don't think they can necessarily be lumped together. One example of an incorrect scientific consensus is the theory of the luminiferous aether. Another false claim was that margarine was healthier than butter. I don't think there is any conceptual tent big enough to cover both of these examples and allow us to say anything meaningful.

Examples like geocentrism going to heliocentrism and aether theories being killed off by relativity were huge revolutions in the foundations of entire sciences. If modern cosmology were to be completely overturned, as I suppose some creationists would like, it would probably require an equally momentous revolution. Historians of science such as Popper and Kuhn have had very different ideas about examples like these.

In Popper's description, scientific theories are falsifiable, meaning that at least in principle, there is some experiment or observation that could disprove it. Popper was trained as a psychologist in the 1920's, when Freudianism was still taken seriously. He would have considered Freudianism not to be a scientific theory, since it was not falsifiable. According to Popper, when an old theory is falsified, what usually happens in the physical sciences is that we find the old theory to have been a good approximation under certain circumstances, which were the circumstances under which it was tested, but a bad approximation under other circumstances. For instance, Newton's laws are an excellent description of the trajectory of a baseball, but a bad description of a subatomic particle moving at half the speed of light. Sometimes this is called the correspondence principle: the old theory wasn't wrong, within the circumstances where it had been accurate, and the new, broader theory has to be backward-compatible with it.

In Kuhn's description, we have paradigm shifts, in which an accumulation of anomalies ends up causing a certain scientific world-view to break down and be replaced by a new one. According to Kuhn, there are periods of normal science, when things are boring and you just go around collecting beetles, and then there are revolutionary periods. Critics seem to see Kuhn as attacking scientific realism, the notion of scientific truth, and the authority of science.

When it comes to climate change, I don't think it would require a scientific revolution to disprove it. It simply looks very unlikely right now that it's wrong. In that sense, it might be more like the margarine-butter example, although probably much less inherently uncertain because the physical sciences don't tend as much toward fads and junk science as does medical science.

I don't think either Popper or Kuhn would have suggested that a consensus among scientists is the right way for scientists to determine what is true in their own field of expertise. I think both were clearly aware of examples like geocentrism and aether theories where the consensus was wrong. If scientific consensus has a place, it's in guiding people who are not scientists, and who therefore can't weigh the published evidence directly or do experiments and observations of their own.

Here are some questions to ask a creationist or climate change denier:

(1) If they don't want to be guided by scientific consensus in matters of science, what alternative guide would they like to use?

(2) What standard of proof do they think is appropriate, and why? In the case of climate change, we're talking about a global crisis, so even if it's only a 99% chance that it's right, it seems to me to make sense to take strong action to keep from driving our planet off a cliff.

(3) On the issue being discussed, is there an alternative theory that fits the evidence? In cosmology, for example, we really don't have a viable alternative right now to a hot big bang.

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  • $\begingroup$ Even if "only" a 99% chance it is right? That is an odd manner of arguing. Do you mean "if only" a 1% chance? $\endgroup$ – KCd Jan 5 '17 at 3:04
  • $\begingroup$ Re: margarine/butter -- was there ever any "science" to "support" it, or was it merely rooted in Depression / wartime propaganda to make butter shortages more palatable? $\endgroup$ – Spencer Jan 5 '17 at 10:59
  • $\begingroup$ @KCd: I say if it's only a 99% chance, because I suspect that an objective analysis by an expert would make it more like 99.9% or 99.99%. $\endgroup$ – Ben Crowell Jan 5 '17 at 15:30
  • $\begingroup$ @Spencer: Interesting question. See hsm.stackexchange.com/q/5547/466 $\endgroup$ – Ben Crowell Jan 5 '17 at 17:36

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