In a previous post, I demonstrated how Bayes formula can be used to show the decomposition of a posterior into a likelihood and a prior. By thinking of a probability as the strength of a belief, we can use this formulation in a loose, non-rigorous sense to describe how a person forms an opinion about intelligent design, creationism, or Darwinism.

Initially, a person has some set of prior deep-seated beliefs. These beliefs can be altered once that person encounters new evidence; in essence, the prior belief evolves to the posterior belief. However, the level of alteration depends on the two factors that we see in the formula: 1) the strength of person's prior belief; 2) the likelihood of the new evidence (which measures how probable the new evidence is, given the person's set of beliefs).

For this post, let me give some examples of prior beliefs.

Creationism:

Christian creationists hold the prior belief that the Bible is true. The strength of this prior belief can depend on how this belief was established (note that even a prior can be decomposed into a previous likelihood and a previous prior). Maybe the belief in the Bible was formed during childhood in Sunday School. A stronger prior belief could be formed by studying Biblical apologetics. Creationists generally also have a respect for science, and they hold a prior belief that science and the Bible can be tightly harmonized.

Darwinism:

Evolutionists hold the prior belief that the origin of life should be explained naturalistically. This prior belief may have been instilled from youth by well-intentioned parents, or it may have been developed in high school or in the university. For instance, Dr. Behe in Darwin's Black Box states:

"Many students learn from their textbooks how to view the world through the evolutionary lens. However, they do not learn how Darwinian evolution might have produced any of the remarkably intricate biochemical systems that those texts describe" (183).

Evolutionists generally believe that any sort of higher power is superfluous to the origin and diversification of life. Some evolutionists also have the prior belief that science and theology should always be separate.

Intelligent Design:

What prior beliefs does an intelligent designist (and one that is not a creationist) bring? The ideal design-theorist should probably have an uninformative prior. In other words, the designist is open to ideas from both Darwinism and creationism. An uninformative prior belief does not prejudge or put prior weight on any position; rather, the evidence leads where it may. Consequently, this position does not rule out the possibility of design in nature. In reality, the typical intelligent design theorist probably has a prior belief that includes a notion of a Designer, but this prior belief is not as strong or as far-reaching as the prior beliefs of creationists.

Other Prior Beliefs:

There are also some unfortunate prior beliefs that are shared by some creationists, IDists, and evolutionists alike. Some are conditioned by popularizers to believe that the other side is always either ignorant, closed-minded, or mendacious. Thus, even before any evidence is presented, a person's mind is already closed. Sometimes, certain labels, like "Young Earth Creationist" or "Atheist," convey connotations that conjure up these unfortunate prior beliefs. Consider a famous saying by Richard Dawkins:

"It is absolutely safe to say that, if you meet somebody who claims not to believe in evolution, that person is ignorant, stupid or insane (or wicked, but I'd rather not consider that)."

In order to have a meaningful dialogue, it is important to remove these unfortunate prior beliefs.

A prior belief that would probably enhance and civilize this dialogue is a belief in fairness and open-mindedness to new ideas. This prior belief essentially undergirds the fundamental purpose of virtually every university. People should be able to present new evidence in a fair environment.

Conclusion

A glance at the formula reveals that the prior holds considerable weight over the strength of the posterior. And it certainly seems like prior beliefs are formed at a young age. Thus, the political controversy between ID and evolution mostly centers around the curriculum in the public school, which is probably the child's primary agent of influence on this issue of origins. The side that is able to most influence the curriculum will probably be the side that wins over the generation. Note that, in one iteration of the formula, the prior has equal weight to the likelihood.

But what if the prior beliefs of a person are already formed and hardened? What can be done to reverse it? In an upcoming post, I will try to look at likelihoods as a way to erode a prior. Of course, this analysis is strictly analogical and non-rigorous.