 Second, it is remarkably difficult to find a suitably neutral positive characterization of what thick concepts are, beyond the idea that they somehow combine evaluation and non-evaluative description. Williams characterizes the application of thick concepts as both “action-guiding” and “guided by the world”: their application depends on the way the world is, but also “if a concept of this kind applies, this often provides someone with a reason for action” (Williams 1985: 140; see also Moore 2006; Heuer 2012; Smith 2013: 102–5). By contrast, the application of thin evaluative concepts is supposed to be purely action-guiding and not world-guided. But moral realists presumably think that the application of thin concepts is also world-guided: whether a thin concept truly applies depends on how the world of objective values lies. Other existing characterizations either suffer from similar problems in failing to characterize thick concepts, or else are either not very informative or too theory-laden (see, e.g., Gibbard 1992, Dancy 1995, Scanlon 2003, Kyle 2020, and for critical discussion Eklund 2011).