We talk and think about our beliefs both in qualitative terms – as when we say that we believe A, or disbelieve A, or are agnostic about A – and in quantitative terms, as when we say that we believe A to a certain degree, or are more strongly convinced of A than of B. Traditionally, analytic philosophers, especially epistemologists, have focused on categorical (all-or-nothing) beliefs, to the almost complete neglect of graded beliefs. On the other hand, the Bayesian boom that started in the late 1980s has led many philosophers to concentrate fully on graded beliefs; these philosophers have sometimes rejected talk about categorical beliefs as being unscientific and as therefore having no place in a serious epistemology.