How many times have we heard this or some variation on it: “I’m no scientist so I follow the scientific consensus against intelligent design.” Or, “I am a scientist so I follow the scientific consensus against intelligent design.” That word, “consensus,” carries tremendous prestige and can be directed like a weapon against any minority view. The logic of consensus, if granted, has the power to shut down discussion of any new idea, resulting in a suffocating conservatism. If it had been maintained consistently across the history of science, we would still believe numerous fallacies held by a consensus of thinkers in the past. Science would truly be stuck.

Those who hold minority opinions argue that the consensus should not be worshipped but questioned. At a time when free speech faces increasing pressure from social media, traditional media, and other power centers, sometimes in the name of the “consensus,” minorities know well the power of groupthink. But I had not before seen a mathematical argument demonstrating the potential of a so-called consensus for abuse.

“Herd Behavior”

Two computer scientists and a mathematician, at Harvey Mudd College and Claremont McKenna College, have published a technical paper, “A Castro Consensus: Understanding the Role of Dependence in Consensus Formation.” They acknowledge the reality of “herd behavior” even among scientists. The title of the paper refers to the way Cuban elections produce landslide victories for the ruling party, by design:

In Fidel Castro’s Cuba, superficially democratic elections unfailingly produced overwhelming support for the Communist Party of Cuba. However, a lack of choices left no other option. In both municipal and national elections, potential candidates had to pass specific requirements and secure backing from government-influenced organizations to be placed on a ballot (Shugerman, 2018; Foundation for Human Rights in Cuba, 2019). Thus, the overwhelming consensus supporting the Cuban Communist Party in elections resulted from political pressure on voters and government restrictions on candidates. The consensus was neither independent nor meaningful.

I should be clear that the authors do not address the evolution debate, or intelligent design. I don’t presume to know their views on that. Instead they say, “Using mathematical modeling, we explore the influence of dependence on the formation of consensus.” Dependence in this context is just the opposite of independence. They launch into a Bayesian analysis of how the dynamic works, and why a consensus can be true or false, depending on how much it relies on pressure and coercion.

Consensus is viewed as a proxy for truth in many discussions of science. When a consensus is formed by the independent and free deliberations of many, it is indeed a strong indicator of truth. Yet not all consensuses are independent and freely formed. We investigate the role of dependence and pressure in the formation of consensus, showing that strong polarization, external pressure, and dependence among individuals can force consensus around an issue, regardless of the underlying truth of the affirmed position. Dependence breaks consensus, often rendering it meaningless; a consensus can only be trusted to the extent that individuals are free to disagree with it.

They explain:

Centuries ago, the Reverend Thomas Bayes derived his namesake theorem to answer the question of whether the testimony of a large number of independent eyewitness could ever establish the probable occurrence of an a priori highly unlikely event. He showed that even highly unlikely events become plausible once the testimony of many independent witnesses is taken into account. Bayes’ theorem has found many real-world uses, including military and medical applications (Cepelewicz, 2016). In agreement with its historical purpose, we use Bayes’ theorem to model how consensus within a population can provide evidence for or against a position. We extend our analysis to dependent models, allowing us to consider the effects of differing levels of dependence, external pressure, and hyper-polarization on the formation of consensus within our framework.

Rare to Nonexistent

They define a “Castro Consensus”: “A Castro Consensus is a near-unanimous show of agreement brought about by means other than the honest and uncoerced judgements of individuals.” 

Again, it’s a technical discussion, and you should review it for yourself, but it confirms common sense. Believing “a large number of independent eyewitness” turns upon the question of whether they are truly independent. Sometimes that’s hard to tell. Other times it’s obvious they are not. In the case of some scientific controversies, such as the one over Darwinian evolution versus intelligent design, we know that genuine independence — freedom from coercion or other social or professional pressures — is somewhere between rare and nonexistent. Evolutionary orthodoxy is maintained by a classic “Castro Consensus.” This by itself makes the Darwinian consensus questionable and in need of a fresh examination.