M. Caelius Rufus to Cicero in Cilicia, written from Rome around the twelfth day before the Kalends of October (roughly 20 September) 50 BC (manuscript dateline Scr. Romae circ. xii K. Oct. a. 704 (50)). Caelius is now curule aedile; the games of section 3 ("at my games at the Circus") are the Ludi Romani of mid-September, which he is presiding over for the first time. The letter is given over entirely to a single grievance: the campaign of his old patron, the censor Appius Claudius Pulcher, against him. Appius — whom Cicero had succeeded in Cilicia, and whose daughter Caelius had once been about to marry — has refused to pay the kindnesses he owes to Caelius, has tampered with the augural college, and has put up a stooge prosecutor to indict him under the Lex Scantinia, a sumptuary statute covering acts contra naturam. Caelius’s reply has been to serve Appius, in his capacity as censor, under the same law.

The voice throughout is Caelius’s at his most direct: short clauses, colloquial scorn ("that ape"), the relish of the political man who has just landed a public counter-blow ("nothing could have fallen out better"). The closing paragraph turns from grievance to the slow communications that have held this letter back forty days, to the looming consular elections (Domitius, who has thrown in with Appius and against him, is dreading them), and to a personal appeal: Caelius asks Cicero to grieve for his injuries as Caelius has been used to grieve for Cicero’s, and to avenge them. The wider crisis — Caesar, Pompey, the provinces — is not in this letter; Caelius will return to it four days later in Ad Familiares 8.14.