Classification work is however not quite as simple as it maylook, on the contrary, it is a rather tricky subject, for wemust give our classes a name, we must define them, we mustknow at any rate ourselves where they begin and where theyend. It would never do for the classes to interfere with each,other, they must be defined so that they neither overlap amongthemselves nor leave any ground of the organisation as a wholeuncovered. That is certainly a difficulty but it is not insur-mountable where patience and perseverance are brought to»bear.