Chapter 6       The First Attack On Bayesianism And How It Is Answered          Part A

The idea behind Bayesianism is straightforward enough to be grasped by nearly all adults in any land. But the idea of radical Bayesianism escapes us. All that you do, mentally, fits inside the Bayesian model, but it is very human to dread such a view of oneself and to slip into thinking that radical Bayesianism must be wrong. We want desperately to believe that at least a few of our core ideas are unshakeable. Too often, unfortunately, people do think that they have found one. But to a true Bayesian, the one truth that he believes is probably absolute is the one that says there are no absolute truths.

An idea is a mental tool that enables you to sort, and respond to, sensory experiences – single ones or whole categories of them. When you find an idea that works, you keep it. What can confuse and confound this whole picture is the way that, in the case of some of your most deeply held ideas, you didn’t personally find them. They came in a trial and error way to some of your ancestors, who found the ideas useful and then did their best to program them into their progeny, etc., and thus they were passed down the generations to your parents, who then programmed them into you.

Every new idea that you acquire gets installed as part of your mental equipment, after careful Bayesian observations and calculations, either by the process of your own noticing, speculating, and testing, or by your family and your tribe programming you with the idea because the tribe’s early leaders acquired that idea by the first process. Consciousness and even sanity are constantly evolving for all humans, all of the time. We keep re-writing our concept sets, from complex ideas like "justice" and "love" to basic ideas like "up" and "down" and even to what I mean by "I". (Individual minds can indeed be made to re-program their notions of “up” and “down”.) (1.) The barest “you” that you are is a dynamic, self-referencing system that is constantly checking your sense perceptions against your ideas about what reality should be and then updating and re-writing itself all of the time.  

And a short side note is in order here. There are also a few commonly used, species-wide ideas, or proto-ideas, that you don't "acquire" by either of the above methods because these ideas are hard-wired into you at birth. These are not programmed into a human by her tribe nor by her own life experiences so they don't fit into either of the categories just described. But they do fit inside the modern empiricist view of what knowledge is simply because in the modern empiricist view, with the models it has gained from Biological Sciences, especially Genetics, these built-in ideas are seen as genetically-acquired anatomical traits and, thus, as subjects for study by geneticists or neurophysiologists. In short, scientists can go looking for them right in the human brain, and they do.

For example, some basic ideas of language are built into all normal humans, but the genes that cause the developing fetus to build the language centers into its developing brain are still being identified. In addition, the structures and functions of these brain areas, once they're built, are only poorly understood. In our present discussion, however, these questions can be passed by. They are biological rather than ideological in nature and, therefore, outside of our present scope. These genes and the brain structures that are built from gene-coded information might someday even be manipulated, either by genetic engineering or some kinds of behavior modifications involving operant conditioning, surgery, drugs, or other technologies we cannot now even imagine.

But whether such actions will be judged right or wrong, and so will be permitted in the normal institutions of our society, will depend on our moral values. These, as we have already seen, are going to need something more at their core than what is offered by Empiricism. As its own moral guide, Empiricism has proved neither sound in theory nor effective in practice. The evidence of human history strongly suggests that Science, at least so far, can't be its own moral guide. This line of thought returns us to our task – discussion of moralities and their sources – and so back to Bayesianism.

So let me reiterate: we are nearly all, nearly all of the time, Bayesians. When an old idea no longer works, we seek, by Bayesian ways, to find a better idea.

          

This Bayesian model of how we think is so radical that at first it eludes us. The idea that I am adjusting my whole mindset all of the time, and that no parts of it, not even my deepest ideas of who I am or what reality is, are ever fully established or reliable is disturbing, to say the least. But this view is the one I arrive at when I look back over the changes that I have undergone in my own life. The Bayesian model of how a “self” is formed, and how it evolves as the organism ages, fits the set of memories that I call “myself” exactly.

            

                                                          Thomas Kuhn

   

Thomas Kuhn was the most famous of the philosophers who have examined the processes by which people adopt a new theory, model, or way of knowing. (2.) His studies focused only on how scientists adopt a new model, but his conclusions can be applied to all human thinking. His most famous book proposes that all of our ways of knowing, even our most cherished ones, are tentative and arbitrary. Under his model of how human knowledge grows, humans advance from an obsolete idea or model to a newer, more comprehensive one by "paradigm shifts", i.e. leaps and starts, rather than in a steady march of gradually growing enlightenment. You "get", and then start to think under, a new model for organizing your thoughts by a kind of conversion experience, not by a gradual process of persuasion and growing understanding. 

It is all very disconcerting. Caution and vigilance seem to be the only rational attitudes to take under such a view of the universe and the human place in it. 

  

Of course, to many people, the idea that all of the mind's systems and systems for organizing systems, and perhaps even its overriding operating system, its sanity, are tentative and are subject to constant revision seems disturbing; some prefer to label it “absurd”. But then again, cognitive dissonance theory would lead us to predict that humans would quickly dismiss such a scary picture of themselves. We don't like to see ourselves as lacking in any unshakable principles or beliefs, changing and evolving from stage to stage in life. But evidence and experience suggest that we are indeed almost completely lacking in such fixed principles or beliefs, and we do nearly always evolve personally in those ways. (Why I say "nearly" always will become clear shortly.)