The Bayesian Model
Chapter 2 introduces the Bayesian Model of rational credence. The mathematical properties of classic probability are explained—their linearity, cardinality, and so on—as well as the use of probability functions to model mental states. A game with balls is created and diagrammed to make visually vivid how probability works. Venn diagrams and truth-tables are used to illustrate everything for the absolute beginner. Conditional Credence is explained with intuitive examples, and the standard ratio formula is introduced. A game with marbles is then created and diagrammed to pump intuition about change of probability, which leads directly to Jeffrey-style kinematics. The chapter closes by describing a notionally possible agent, Creda, whose psychology matches the Bayesian Model.