 Some taxonomies are merely descriptive, and they tend to be less controversial. For example, Kendall Walton (1990) distinguishes between spontaneous and deliberate imagining (acts of imagination that occur with or without the one’s conscious direction); between occurrent and nonoccurrent imaginings (acts of imagination that do or do not occupy the one’s explicit attention); and between social and solitary imaginings (episodes of imagining that occur with or without the joint participation of several persons).