nec liber ut fieret, sed uti sua cuique daretur
littera, propositum curaque nostra fuit.
postmodo collectas utcumque sine ordine iunxi:
hoc opus electum ne mihi forte putes.
da ueniam scriptis, quorum non gloria nobis
causa, sed utilitas officiumque fuit.
(51-56)
Ovid's explanation is reasonable enough, and is confirmed by the speed with which he composed the first three books of the Ex Ponto once he knew that it was safe to name people in his verse. The first three books of the Ex Ponto, like the Tristia, were written with the single objective of securing Ovid's recall, and this naturally caused a certain repetition of subject-matter.
By the time Ovid wrote the poems that would form the fourth book of the Ex Ponto, he had lived in Tomis for six or more years, and it must have been clear to him that his chances of recall were slight. The result of this is a diminished use of his personal situation as a theme for his verse. Often he introduces his plight in only one or two distichs of a poem, subordinating the topic to the poem's main theme. The result of this technique can be seen in such extended passages as the descriptions of the investiture of the new consul (iv & ix), the address to Germanicus on the power of poetry (viii), or the catalogue of poets that concludes the book. In all of these passages Ovid's desire for recall is only a secondary theme.
The mixing of levels of diction
As well as variety of subject, the fourth book of the Ex Ponto shows a variation in style that is typical of Ovid's letters from exile. The poems use the metre and language of elegiac verse. But at the same time they are letters, and are strongly influenced by the structure and vocabulary of prose epistles. This influence is naturally more obvious at some points than at others; and even within a single poem there can be a surprising degree of variation in the different sections of the poem.
Some poems tend more to one extreme than the other. The eleventh poem, a letter of commiseration to Gallio on the death of his wife, is extensively indebted to the genre of the prose letter of consolation; this prose influence is evident in such passages as:
finitumque tuum, si non ratione, dolorem
ipsa iam pridem suspicor esse mora
(13-14)
At the opposite extreme is the final poem of the book, a defence of Ovid's poetry; as this was a traditional poetic subject, the level of diction throughout the poem is extremely high, particularly in the catalogue of poets that forms the main body of the poem.