 The orthodoxy on imagination and memory in the history of philosophy, however, is discontinuism, a view on which there are significant differences between imagination and memory, even if there are overlaps in their psychological mechanisms. Some philosophers find the distinction in internalist factors, such as the phenomenological difference between imagining and remembering. Most famously, David Hume sought to distinguish the two in terms of vivacity—“the ideas of the memory are much more lively and strong than those of the imagination” (Treatise of Human Nature: 1.3; but see Kind 2017). Others who have adopted a phenomenological criterion include René Descartes, Bertrand Russell, and William James (De Brigard 2017). Other philosophers find the distinction in externalist factors, such as the causal connection that exists between memories and the past that is absent with imagination. Aristotle uses the causal connection criterion to distinguish between imagination and memory (De Anima 451a2; 451a8–12; see De Brigard 2017). Indeed, nowadays the idea that a causal connection is essential to remembering is accepted as “philosophical common sense” (see the entry on  memory;  but see also De Brigard 2014 on memory traces). As such, it is unsurprising that discontinuism remains the orthodoxy. As J. O. Urmson (1967: 83) boldly claims, “One of these universally admitted distinctions is that between memory and imagination”.