(This is a revision of something I wrote three years ago.)
“With respect to science, the assumption behind consensus is that science is a source of authority and that authority increases with the number of scientists. Of course, science is not primarily a source of authority. Rather, it is a particularly effective approach to inquiry and analysis. Skepticism is essential to science; consensus is foreign.”
“With respect to science, consensus is often simply a sop to scientific illiteracy. After all, if what you are told is alleged to be supported by all scientists, then why do you have to bother to understand it? You can simply go back to treating it as a matter of religious belief, and you never have to defend this belief except to claim that you are supported by all scientists except for a handful of corrupted heretics.”
– Richard S. Lindzen, “Climate Alarm: Where Does it Come From?”, lecture presented to the Marshall Institute on 1 December 2004
The second of these two paragraphs is sort of true, in the sense that as a practical matter most of us defer to the consensus reached by scientists rather than going to all the trouble of retracing each and every one of their steps by which they reached that consensus – i.e., we’re too busy or too lazy or (sometimes) insufficiently trained to repeat their work, to confirm it by the same repeatable methods involved in their peer review, which led to the consensus, and thus we “must”, in a sense, “take it on faith”, despite the fact that we could in theory confirm it ourselves.
But the trouble with Lindzen’s argument overall is that it conflates evidence with those who present it. It’s the preponderance of evidence, gathered collectively via the scientific method, that should be convincing, not the preponderance of scientists themselves, simply as an aggregate of individuals. Thus I have to disagree: it is indeed science that is the source of authority, just not the scientists themselves. This IS a meaningful distinction.
It’s their method that matters, a method which has the skepticism to which Lindzen refers built into it already, not their numbers. Reality is independent of the percentage of people who see it, whether that percentage is large or small, and the scientific method has been shown time and time again to be our best means to approach that reality. It’s true enough that you shouldn’t necessarily believe something to be true just because a majority or even a totality of a group of people believe it (something that is the bulk of the persuasive force of religion, for instance), but in the case of science and scientists, it is NOT simply a matter of belief. Thus, consensus is NOT merely “a sop to scientific illiteracy”; that assertion is a slippery, and, I think, borderline dishonest bit of rhetorical sleight-of-hand:
Lindzen posits a curious, and I think unwarranted, opposition between skepticism and consensus, one which ignores the temporal sequence in which they operate, one in which they operate complementarily. As I imply in my title, scientific consensus is NOT merely belief en masse. It’s not merely possible, but highly probable and necessary for a group of scientists to come up with a consensus – one which, like all scientific conclusions, is provisional, open to revision – which is itself the product of a long process involving skepticism at every step of the way. The better that a group of scientists practices the scientific method, the more skepticism will be involved in the formation of whatever consensus is reached. It’s very likely they will have engaged in very sharply critical debates along the way, but at some point, consensus IS reached. Science doesn’t just consist of endless arguments; agreements are reached as well. Otherwise, no advances would ever be made! The scenario that Lindzen seems to be implying here, of conclusions being reached en masse with little or no skepticism involved, whereupon the brave (and presumably vastly in the minority) skeptics step in to question it all, is just silly. It’s just not the way it works. Scientists are already plenty skeptical. It’s just that their skepticism has a goal: the reaching of a well-founded consensus. It’s absurd to say that “consensus is foreign” to science. Actually, good consensuses (consensi?) are the main POINT of science. They are always open to revision, but that doesn’t mean that they aren’t valid at all.
(The deniers who call themselves skeptics also have a goal, but it is not the honest one of reaching a well-founded consensus. Their goal is usually the defence of their status quo. They use the terminology of the scientific method to make their armchair critiques seem thoughtful and constructive, but closer examination reveals a lack of the kind of critical efforts in which real scientists must and do engage. They don’t do their homework; a hallmark of their debating techniques is to throw the burden of proof onto whomever challenges them, asking for citations, etc., when they’ve already had plenty of opportunities to seek out the documentation themselves, to come to the debate already having done the relevant research of readily available sources, IF they were truly sincere.)
Lindzen asks, “if what you are told is alleged to be supported by all scientists, then why do you have to bother to understand it?” Well, the point he omits is that you CAN understand it, should you take the trouble and time to do so. The scientific method is just as available to you as it is to them. You can read their papers; you can follow their reasoning. Science works, and works best, by open review. If you bother to make the effort, you can read the IPCC reports. They’re freely available. If you don’t, that’s your problem. It’s not a valid critique of the reports to say that they are the result of some mass collusion to agree on some pre-arranged, politically motivated conclusion, as many deniers (who incorrectly call themselves skeptics) do. How would you know that unless you read them and checked them out yourself? You have no prior reason to believe that such a nefarious conspiracy exists – other than your own resistance to having to re-examine your own comfortable existence – and that’s insufficient. Skepticism in good faith (so to speak; I’m not invoking faith in the sense of unsupported belief), as opposed to emotional resistance to one’s pre-existing assumptions (“It’s just sunspots! I can go on driving my Hummer!”) being challenged, involves taking a serious look at the evidence whenever a scientist raises an alarm based on his analysis of it. Skepticism is NOT merely thinking, oh, well, they must be conspiring, therefore I don’t need to look at what they’re presenting. One has a responsibility to meet scientists on the common ground of the scientific method if one’s critique of their conclusions is to have any validity.
A scientist may certainly believe in a conclusion once he or she is satisfied that the criteria required by the scientific method have been met, but belief, whether individual or en masse, is not the source of the conclusion’s truth; rather, it’s a consequence of it. It should be kept in mind that the methods that individual scientists use are independent of the contingent facts of who they are; another person equally well-versed in those methods should be able to and will reproduce the same results, the same conclusion from the same evidence, to the degree that their efforts aren’t clouded by prejudice and unwarranted assumptions and what Richard Feynman referred to as one’s tendency to fool oneself first of all.
Thus, it is the scientific method itself which is the source of authority, not the scientists who wield it. The consensus we speak of – e.g., the IPCC reports – is a consensus of facts and their implications (what we call a “theory”, which is not the same as a mere guess), not merely a consensus of a group of people’s opinions. The authority resides only in the well-formulated and well-tested theory, and not at all in whoever comes up with it. (If someone other than Newton had come up with the laws we refer to as his Three Laws, they would be just as valid.) If a scientist who has produced a good theory before comes up with a clunker on her next attempt, the validity of the earlier theory does not magically accrue to the new, flawed one. The new one has to stand on its own, and in no case does any authority reside in the scientist per se. It resides in her results to the degree that they are the product of good methods.
If you ignore what it is that is unique to the practice of science, then yes, it’s possible to make the mistake of saying that accepting what a majority of scientists say is no different than accepting what a majority of priests say. It IS different, and it is the independent scientific method which makes it so.