The poem which follows Pearl in the Cotton Nero manuscript presents a number of peculiar difficulties, including, for editors, the problem of what to call it. In the very first line, it announces its subject: ‘clannesse’. ‘Clene’, ‘clanly’, and ‘clannesse’ do indeed recur throughout as keywords; yet they cover a range of meanings which the same words in modern English cannot match. They denote in the poem a variety of physical properties, including freedom from dirt on such things as clothes and dishes, smoothness of surface, and high polish; but they also denote a variety of moral and spiritual conditions, including freedom from sexual sin. Richard Morris, the first editor of the poem, called it ‘Cleanness’, a decision followed by most recent scholars. However, that title, for a modern reader, leans heavily towards the physical meanings. The alternative, adopted by Menner in his excellent 1920 edition, is to call the poem ‘Purity’; but here the modern word leans too far towards the moral and spiritual side. This is more than a mere dilemma for editors: their terminological difficulty reflects the fact that the poem displays a particular complex of interrelated ideas, physical and moral, which has largely broken up in modern times. Indeed, some recent critics, as we shall see, have turned to the anthropologists in order to make sense of it. In the circumstances, for lack of a properly comprehensive term, one might as well follow the poet's own usage, and that generally favours the vernacular ‘clean’ and its derivatives rather than the Franco-Latin ‘pure’. ‘Cleanness’ does, as a title, sound odder than ‘Purity’; but then the poem itself is rather odd.

Cleanness differs from the other poems in the manuscript most of all in its structure. Pearl, Patience, and Sir Gawain all confine themselves strictly to a single, continuous sequence of events; but Cleanness attempts no such unity of action. It draws upon the Bible for a number of distinct stories, taking narrative examples mainly from the Old Testament to illustrate its argument. These biblical episodes are selected to display God as a preserver and destroyer of men, and most especially as the destroyer of those who behave ‘uncleanly’. The three central stories are: Noah's flood, Sodom and Gomorrah, and Belshazzar's feast.