 Second, Hume suggested that memory and imagination may be distinguished by the former’s higher degree of vivacity. As Pears (1990) points out, Hume’s notion of vivacity is ambiguous. It sometimes seems to refer to a property of the representation produced by the apparent memory process; the idea here would be that representations produced by remembering are more detailed than representations produced by imagining. But it sometimes seems to refer to a property of the apparent memory process itself; the idea here would be that remembering imposes itself on the subject in a more spontaneous manner than does imagining. On either interpretation, vivacity may have merit as a first-person memory marker, but it is unworkable as a third-person marker. The representations produced by remembering may be more detailed on average than the representations produced by imagining, but only on average: imagination sometimes produces representations containing a great deal of detail, and memory sometimes produces representations containing very little detail. Similarly, the process of remembering may on average occur spontaneously more often than the process of imagining, but only on average: we sometimes remember deliberately, and we sometimes—as in the familiar phenomenon of mind-wandering (Dorsch 2015)—imagine spontaneously.