Many important distinctions, which are not immediately obvious, between types of social situation or relationships may best be brought to light by an examination of the standard uses of the relevant expressions and of the way in which these depend on a social context, itself often left unstated. In this field of study it is particularly true that we may use, as Professor J. L. Austin said, ‘a sharpened awareness of words to sharpen our perception of the phenomena’.

H. L. A Hart, The Concept of Law, loc. 23