Ernie is a law-producing machine who churns out legislation at random. People put things into Ernie and Ernie puts things out. Ernie does not always connect two things put in on different occasions. Ernie does not put the law out in order. Ernie has not thought much about classification. How can classification help Ernie? Or does Ernie need help ? This paper started life because it was thought that if Ernie reflected on the process in which he is engaged he might improve his ways. Sornetimes in the past Ernie has shied away froni introspection, perhaps because he remembered the fable of the centipede who became paralysed when he started to wonder how he co-ordinated his legs. Sometimes Ernie has merely been impatient of theory. ln this paper we are concerned with sorne general aspects of classification as a preliminary to detailed discussion of specifie problems. We do not know whether the ideas put forward will be of much immediate practical value to Ernie, but there need be no fear (nor hope) that Ernie will grind to a haIt through worrying about his production methods.