#rationality #mathematic #probability # [[Epistemic status]] #shower-thought # Related - [[Philosophy/Rationality/Probability is an useful illusion]] - [[Mathematic/Causality/Probability/Nonpsychological probability]] - [[Philosophy/Rationality/Decision theory]] - [[Philosophy/Rationality/Models/Conjunction fallacy]] # Probability theory >Let "P (such-and-such)" stand for "the probability that such-and-such happens," and P(A, B) for "the probability that both A and B happen." Since it is a universal law of probability theory that P(A) > P(A, B), the judgment that P(Bill plays jazz) is less than P( Bill plays jazz, Bill is an accountant) is labeled incorrect. To keep it technical, you would say that this probability judgment is non-Bayesian. Beliefs and actions that are rational in this mathematically well-defined sense are called "[[Bayes theorem|Bayesian]]." >~ [[Eliezer Yudkowsky]]