The non-cognitivist approach may already be found in Hume's "Is-ought problem", but received its most influential analytic formulations in works of A. J. Ayer, C. L. Stevenson, and R. M. Hare, who focused on abstract or "thin" ethical concepts such as good/bad and right/wrong. These allegedly had special practicality or link to action that could not hold a "matter of fact". The non-cognitivists or emotivists so argued that corresponding expressions are not employed to affirm something true of a thing in question, but rather to express an emotion or an imperative in Hare's case. Clearly, the form of an imperative can apply to any description of action irrespective of content. So "morality" and "the facts" are quite independent of each other.