 Philosophers generally distinguish among three main kinds of memory. In early treatments, Bergson ([1896] 1911) and Russell (1921), for example, distinguished between habit memory and recollective memory, while Broad (1925) and Furlong (1951) further distinguished between recollective memory and propositional memory (cf. Ayer (1956; D. Locke 1971)). These distinctions align reasonably well with those drawn by a taxonomy which, originating in psychology, has increasingly become standard in more recent philosophy.