 The doctrinal, taxonomic and (various) sociological concepts of law do not exhaust the possible concepts that might be useful. Obviously, we require, for instance, an evaluative concept of law that identifies the value of legality. Similarly, some legal philosophers, such as Raz and Coleman, understand the inquiry as an investigation of a folk concept of law that underlies ordinary usage of the term. This folk concept will differ from the other concepts of law but it may be influenced (or perhaps tainted) by the others, particularly the doctrinal and evaluative concepts. Kornhauser [forthcoming] offers an achievement concept of law according to which law is a contingent achievement of a functioning governance system in specific circumstances. It realizes some value of legality. This view is elaborated at greater length in section 3.3. 