Most people never attempt to be as precise as Brian, preferring to stick with what they know, which is the two- or three-setting mental model. That is a serious mistake. As the legendary investor Charlie Munger sagely observed, “If you don’t get this elementary, but mildly unnatural, mathematics of elementary probability into your repertoire, then you go through a long life like a one-legged man in an ass-kicking contest.”23
