Bayesianism can coherently express what minds do, if first we accept that such things as minds exist. Bayesianism can’t pin down in an infallible definition what a mind is. In the rough Bayesian view, the mind is a program capable of data processing, manipulation, and storage, running on a constantly active, probability-calculating platform system, deciding second by second which applications to use and which files to open, always aimed at prime objectives of self and species perpetuation. It manifests itself in the material world, specifically in the chemistry of my brain, whenever I physically see, hear, feel, smell, or taste a bunch of sense data and then spot a pattern in them. Sometimes, in events around me, I even see a new pattern and experience what is usually called a causal connection. This brain chemistry change is experienced subjectively as an “Aha! moment.” It is a trait of life, and most especially, of human life. No computer program, so far, can imitate it.

However, Bayesianism does not pretend to say in any more precise detail what a mind is.

The human mind is ultimately its own greatest mystery. Or rather, as nearly as minds can make out, the mind is one of the most successful manifestations of that greater mystery, life itself. It is an entity whose precursors are built into the human genome. Once the basic neurological structure is built, once the baby is born, the brain is stocked with cultural programming authored by the ancestors of that human’s society. The being that results is driven by its very nature to seek a healthy direction, from the molecular level on up to cells, organs, the individual, her family, her society, and her species, to learn and grow. Why? We don’t know. Life’s love of itself is an unanalyzable given.

A miracle, by definition, is an event that seems incorrigibly to defy all rational and empirical explanation. For us today, old-style miracles likely are over. But the most amazing phenomenon that a modern human mind will ever encounter, but never truly know, is itself. You are your own greatest wonder.

In furthering our goal of constructing a moral code that is founded on our best understanding of reality, these last three chapters have served only one purpose. They have left us with a model of the mind—and what it does as it thinks and “knows”—called Bayesianism.

The most paralyzing confusion in my mind about how to best realize my prime directive occurs when I am trying to decide between the preservation of myself and that of others outside myself. Even deeper than our minds is the basic programming of sex and reproduction. We’re built to love our kids, and since we want them to survive so much, we learn to be motivated about the survival of our tribe. Gradually, as we mature, we learn to expand this circle of moral consideration to our nation. Our most interesting literature dramatizes situations that portray heroes trying to sort through choices between their own survival and that of their friends, families, or nations. We find them challenging and fascinating. In such literature, we are seeking models to guide us through possible future situations in which we may have to choose between saving ourselves and saving our children, our nation, or our species. I, like all my fellow humans, want to live. But I want my kids and my country and its way of life to survive too. 

Bayesian decision processes get confused in such dilemmas. We feel this confusion as what we call “anxiety”.  

Shakespeare’s Hamlet still holds the stage for exactly this reason. Hamlet can’t see any point in this life of treachery in which the bad succeed by being bad. But in the end, he realizes he is willing to die for the restoring of order in his beloved country, Denmark. The rest he will leave for God to sort out.

There are, of course, no neat, simple answers to such questions, no unfailingly reliable guides. Reality is uncertain, subtle, complex, and frightening. No sets of programs we can devise will ever enable us to live in reality without running into anxious challenges and rude surprises. 

Still, the bottom line is that reality is where we must live. Therefore, in our universe, it is sad but true that a moderate but constant anxiety is the natural human condition. Anxiety is the downside for us of surviving in the probabilistic real world. The upside is freedom. If we are brave enough, we learn to relish life as challenge.

As far as this book is concerned, the important point to be made about Bayesianism is that the Bayesian model of the human mind is the one on which this book is founded. For each of the further points I argue in this book, I will try to show that they currently appear to have the best odds of working in the future, not that any one of them is irrefutably logical. To aim for logically irrefutable conclusions is to violate the spirit of Bayesianism—and to waste one’s time. In this life, any search for perfect confidence in any belief is either deluded or doomed to cycle after cycle of circularity, frustration, and failure.

Therefore, we must aim to adopt beliefs that, when they are used to construct arguments, make our conclusions look increasingly probable the more we check those conclusions against wider observations of physical evidence. Higher levels of probability are what we want, probabilities that appear to keep climbing the more of the real world we explore and successfully cognize.