Chapter 8      How Pervasive Is Bayesianism?

   

   

                                              girls learning sign language 

                              (credit: David Fulmer via Wikimedia Commons) 

The idea behind Bayesianism is straightforward enough to be grasped by nearly all adults in all lands. But radical Bayesianism escapes us. The radical form of Bayesianism says all we do fits inside the Bayesian model. But it is very human to dread such a view of ourselves and then to slip into thinking Bayesianism must be wrong. We want desperately to believe that at least a few of our ideas are unshakable. Too often, unfortunately, people think they have found just such an idea. But a true Bayesian believes that probably the only absolute truth is the one that says there are no absolute truths. However, we use familiar ideas and beliefs to interpret, reason, and act in the world because we have to. 

An idea is a mental tool that enables you to sort, and respond to, sensory experiences – single ones or whole categories of them. ("Ah. Balsamroot. Tasty.) (Yipe! Over here, poison ivy. Stay away.") ("Now that's real courage.")

When you find an idea that enables quick, accurate sorting, 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, deeply programmed ideas, you didn’t personally find them. They came in a trial-and-error way to some of your ancestors, who found the ideas so useful that they then did their best to program these ideas into their children. Then, they were passed down the generations to you.

Many ideas you consciously acquire are added to your mental toolkit after careful Bayesian analysis, by the process of your own noticing, considering, and testing them. Then, mostly unconsciously, you pick up many more ideas that come to you from your family and tribe. This cultural programming is being instilled in you because people of your tribe acquired, tested, and affirmed that idea by the first process. 

Observe, hypothesize, test, adjust, test some more: these are the marks of Bayesianism on the individual, tribal, and species-wide scales.

Culture, consciousness, and even sanity are constantly evolving for all humans, all the time. Each of us keeps rewriting beliefs, from complex ones like justice and love to ones as basic as up and down. (Individual minds can indeed be made to reprogram their notions of up and down.¹) I is a dynamic, self-referencing system that is constantly checking its perceptions of reality against models and concepts of what it believes reality should be, then updating itself.

A short side note is in order here. This is the place to admit that a few widely shared concepts are not acquired by either of the above methods, but instead are hardwired into us in our genes. These are not programmed into us by our tribes nor by our own experiences, so they don’t fit into either of the categories just described. But they do fit inside the Empiricist view because they can be studied by scientists using Empiricist methods, for example, by people like neurologists. We can find the spots in the brain where certain very widely held concepts reside.

For example, some basic ideas of language are built into all normal humans. We also innately fear snakes and heights. Some of the genes that cause language centres to develop in the fetus’ brain are still being identified. The brain areas holding these innate ideas are also only partially understood. But they are being found and studied (e.g. Broca’s area). They are not Rationalist-type mysteries.  

In our present discussion, however, we can pass these innate concepts by. They are biological rather than philosophical – hardware rather than software – so they are outside of our present scope. These genes, and the brain structures that are built from the information coded in them, could even be manipulated one day, for a whole range of possible ends, by genetic engineering, behavior modification, drugs, surgery, or even other technologies we cannot now imagine.

But for our purposes here, in our search for a universal code of moral values, neurophysiology’s usefulness at this point runs out. Whether techniques for manipulating the human brain will be judged right or wrong and whether they will be allowed in our society will still depend on values already programmed as “software” into future tribes of humans. Values like freedom and human dignity. These values, as we have already seen, are going to need something more at their core than what is offered by our current Science.

I repeat: Empiricism, as a moral guide, has proved unreliable in theory and practice. In short, so far, Science has failed at being its own moral guide.

Even in the branch of Science called neurophysiology, the structure of the human brain cannot tell us how human brains should be used. By drawing an analogy between Computing Science and neurophysiology, we see that brains are hardware while moral codes are software. What we should program into the hardware is not made clear by studying the hardware. That whole line of thought requires that we examine the fit between our software – our moral codes – and the higher order reality, i.e. the world. Do our morals work? Do they lead us to live healthier, wiser lives and, most of all, to survive? In the end, that is the only important test of any moral code. This line of thought returns us again to our discussion of the foundations of moral codes – and so to Bayesianism. 

The Bayesian model of how we think is so radical that at first it eludes us. To each individual, the idea that she must continually adjust her entire mindset, and that no parts of it, not even her most deeply held ideas of who she is or what reality is, can ever be fully trusted is disturbing to say the least. Doubting our most basic concepts is a kind of flirting with mental illness. Even considering the possibility is upsetting. But this radical Bayesian view is certainly the one I arrive at when I look back honestly over the changes 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 my “self” exactly.

Thomas Kuhn is the most famous of the philosophers who have examined the processes by which people adopt a new theory, model, or way of knowing. His works focused only on how scientists adopt a new scientific model, but his conclusions can be applied to all thinking. His most famous book proposes that all our ways of knowing, even our most cherished ones, are tentative and arbitrary.² Under his model of how human knowledge grows, humans advance from an obsolete idea to a newer, more effective one by paradigm shifts – by leaps, rather than in a steady march of gradually growing understanding. We “get”, and then start to think under, a new model not by gradual learning, but by a kind of conversion experience very like a religious conversion.

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. To many people, the idea that all the mind’s routines, all its systems for organizing its sense data, and then the more general systems that enable it to organize other systems, and perhaps even the mind’s operating system – i.e. its sanity – all are tentative and subject to constant revision …this idea seems more than disturbing; it seems absurd. 

But then again, cognitive dissonance theory leads us to predict that we would dismiss such a scary picture of ourselves. We don’t want to see ourselves as incapable of forming any solidly reliable beliefs. However, both experience and History suggest we are indeed almost completely devoid of any unshakable concepts or beliefs. (Why I say almost completely will become clear shortly.) 

To conclude this chapter then, we can say that our way of thinking in all matters is ultimately always Bayesian; in our real existence, there is no other way.

At this point in the discussion, opponents of Bayesianism begin to marshal their forces. Critics of Bayesianism give several varied reasons for continuing to disagree with the Bayesian model, but I only want to deal with two of the most telling – one is practical and evidence-based, and the other is theoretical.

So let us now deal with the attacks from the anti-Bayesians, the evidence-based attack in the next chapter, and the theoretical one in the chapter after that.

Notes

1. Jan Degenaar, “Through the Inverting Glass: First-Person Observations on Spatial Vision and Imagery”

Phenomenology and the Cognitive Sciences 12, No. 1 (March 2013).

2. Thomas Kuhn, The Structure of Scientific Revolutions (Chicago: University of Chicago Press, 3rd ed., 1996).