The question of expertise—its nature, scope, and application—is one of the most urgent issues in the modern world. The recognition of expertise as an important issue and the analyses of its problems are firmly embedded in the Western tradition. Plato's discussions of techné and of the difference between philosophy and sophistry, for instance, are best characterized as discussions of expertise. "When Socrates seeks moral knowledge," Julia Annas writes, "it is only to be expected that this will be seen on the model of practical expertise, since this is the model for knowledge in general" (Annas 2001, p. 245).

In its modern usage, the word expert derives from the Latin expertus, the past participle of experiri, "to try"; an expert is one who has been tested and become skilled or knowledgeable through experience. Although this definition seems straightforward, in the real world experts are not always easy to identify...