M. Brutus to T. Pomponius Atticus — not to Cicero — written from somewhere in Brutus’s eastern command, in May or June 43 BC. The Perseus dateline reads Scr. m. Maio, ut videtur, a. 711 (43), “written in the month of May, so it appears,” 43. The meta entry’s year-precision placeholder of 6 October must be corrected to mid-43; the letter has nothing to do with the autumn proscriptions and predates them by months. It belongs in Ad M. Brutum only because, alone among Brutus’s letters to Atticus, it survived in the same archive as the Brutus–Cicero correspondence and was inserted into the book on textual rather than chronological grounds.

This is the most politically charged document in the surviving corpus of Brutus. The occasion is Atticus’s report that Cicero is hurt at Brutus’s silence on his political conduct; Brutus, under Atticus’s pressure, writes out at last what he really thinks. The criticism is comprehensive. (1) Cicero has irritated the young Caesar’s appetite for power rather than checked it. (2) Cicero’s strategy of cultivating Octavian as the counterweight to Antony has been not merely a mistake but a folly: he has stood forth as the avenger of one evil only to become the founder of another whose roots will go deeper. (3) The triumph voted to Octavian, the soldiers’ pay he has authorised, the decrees encouraging him not to “be ashamed of coveting the fortune of the man whose name he has taken up” — this is not the conduct of a consular, of Cicero. (4) Cicero, like all old men who have property, children, and honours, is afraid of the three evils Brutus lists with a Stoic philosopher’s unflinchingness: death, exile, poverty. Out of that fear he has come to think it the worst of all evils to lose what he has, and so will tolerate servitus, if only it is honourable. (5) The famous taunt of the central section: “We do not boast of the Ides of March at every hour, as Cicero has the Nones of December always on his tongue,” contrasts Brutus’s tyrannicide and Cicero’s suppression of the Catilinarian conspiracy on equal historical footing — and Brutus on the better side of the comparison.

The letter is dated by its political content to the weeks when news from Italy made the trajectory clear: Octavian had been refused the consulship in the spring, the Senate had begun showering him with extraordinary honours rather than concede the office, and Brutus had begun to see what that combination of refusal and flattery would yield. The closing section, with its solicitous question about Atticus’s daughter Attica’s betrothal and its concern for Brutus’s wife Porcia, gives the personal frame: Atticus and Brutus are the closest of friends, and the letter is an attempt to enlist Atticus in the cause of restraining Cicero. The attempt failed. Within a year, Brutus’s prediction — that Cicero would fall under the proscriptions of the master he had helped to make — came true. The text in section 6 carries an unresolved crux at “Antonius,” here preserved.