Bayesian Updating

The Basic Movement

Bayesian updating moves from prior confidence through new evidence to posterior confidence. The direction and size of the movement depend on how strongly the evidence favors one hypothesis over alternatives.

The formal mathematics can be precise, but the practical habit is already valuable: start with base rates, compare likelihoods, update proportionally.

Common Updating Errors

People often update too much from vivid anecdotes, too little from statistical evidence, too much from identity-confirming information, and too little from disconfirming information. They also ignore the prior when the new evidence feels dramatic.

These are not merely math errors. They often reflect the entanglement of Deep Rationality and Core Rationality: weak tools mixed with protective motivation.

Updating as a Discipline

Updating is not a one-time concession. It is a posture of continued answerability. The rational agent remains available to evidence, but not gullible before every new signal.

Adjacent References

These are starting points rather than exhaustive citations. They connect this page to nearby work in probability, calibration, cognitive bias, and social epistemology.

• |Thomas Bayes, "An Essay towards solving a Problem in the Doctrine of Chances" (1763).
• |E. T. Jaynes, Probability Theory: The Logic of Science (2003).