The Bayesian way of thinking about our own thinking requires us to be willing to float all our concepts, even our most deeply held ones. Some are more central, and we stand on them more often and with more confidence. A few we may believe almost, but not quite, absolutely. But in the end, none of our concepts is irreplaceable.

For humans, the mind is our means of surviving. It will adapt to almost anything.

We gamble heavily on the concepts we routinely use to organize our sense data and memories of sense data. I use my concepts to organize the memories already stored in my brain and the new sense data that are flooding into my brain all the time. I keep trying to acquire more concepts – including concepts for organizing other concepts – that will enable me to utilize my memories more efficiently to make faster and better decisions and to act increasingly effectively. In this constant, restless, searching mental life of mine, I never trust anything absolutely. If I did, a simple magic show would mesmerize and paralyze me. Or reduce me to catatonia.

When I see elephants disappear, women get sawn in half, and men defy gravity, and all come through their ordeals in fine shape, some of my most basic and trusted concepts are obviously being violated. But I choose to stand by my concepts in almost every such case, not because I am certain they are perfect but because they have been tested and found effective over so many trials and for so long that I’m willing to keep gambling on them. I don’t know for certain that they are sure bets; they just seem like the most promising options available to me.

                           

                                                    Harry Houdini with his “disappearing” elephant, Jennie 

                                                                           (credit: Wikimedia Commons)

Life is constantly making demands on me to move and keep moving. I have to gamble on some things; I go with my best horses, my oldest, most successful and trusted concepts. And sometimes, I change my mind.

This mental flexibility on my part is just life. Bayesianism is telling us what Thomas Kuhn said in The Structure of Scientific Revolutions. We are constantly adjusting all our concepts to try to make our ways of dealing with reality more effective.

And when a researcher begins to grasp a new hypothesis and the model or theory it is based on, the resulting experience is like a philosophical or religious “awakening”—profound and even life-altering. Everything changes when we accept a new model or theory—because we change. In order to “get it,” we have to change. We have to eliminate some of the old beliefs from our familiar background set.

And what of the shifting nature of our view of reality and the gambling spirit that is implicit in the Bayesian model? The general tone of all our experiences tells us that this overall view of our world and ourselves, though it may seem scary or perhaps, for more confident individuals, challenging—is just life.

We have now arrived at a point where we can feel confident that Bayesianism gives us a good base on which to build further reasoning. Solid enough to use and so to get on with all the other thinking that has to be done. It can answer its critics—both those who attack it with real-world counterexamples and those who attack it with pure logic.

So here is a good place to pause to summarize our case so far in a new chapter devoted just to that summing up.

Notes

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