Marcus Caelius Rufus (c. 88–48 bc) is the author of seventeen letters to Cicero preserved in Book 8 of Cicero's Epistulae ad familiares, totalling thirty pages in the Oxford Classical Text. We also possess nine letters of Cicero to Caelius (Fam. 2.8–16, eighteen pages OCT), three of which are reactions to preserved letters of Caelius. I will be concerned with those letters that were exchanged between the two when Cicero was proconsul in Cilicia (fifteen letters by Caelius – total number of words 5,275 – and eight by Cicero – 2,011 words), written between May 51 bc and November 50 bc. The size of the two corpora is large enough and the circumstances in which they were writing were sufficiently stable to see whether there are differences between the language of the two men.

Caelius had a good reputation as orator, as is testified by Cicero himself and by Quintilian: