Cicero to M. Junius Brutus, written from Rome on 14 April 43 BC — Perseus dateline Scr.\ Romae xviii K.\ Mai.\ a.\ 711 (43), confirmed by the closing subscript XVIII Kalend.\ Maias and matching the meta date. The letter is among the most politically weighted of the surviving correspondence with Brutus: a manifesto and a reproach, written in the brief window between the news of Forum Gallorum (the battle fought on 14 April outside Mutina, in which Antony was checked but not yet broken) and the news of Mutina proper (21 April). The Ides of April scene Cicero describes in sections 3 and 4 — the surprise reading-out of letters from both Brutus and Antony, the latter styled Antonius proconsul — is the political crux of the letter: an attempt by some intermediary, here Celer Pilius, to draw the Senate into recognising Antony’s continued proconsular standing while the war was still being fought.

The letter’s argument runs in two arcs. Sections 1 and 2 are the apologia: Cicero recalls that he and Brutus agreed on the end — the liberty of the commonwealth — but differed on means after the Ides of March, when Brutus chose to spare Antony and Cicero (he says) wanted the kingship abolished along with the king; “which choice would have been better we felt then to our great pain, we are feeling now to our great peril.” The intervening sentence on Octavian — nisi Caesari Octaviano deus quidam illam mentem dedisset — gracefully credits the young Caesar with the heaven-sent inspiration that has saved them from Antony, with no hint of the misgivings Brutus already entertains and will soon urge in reply. Sections 3 and 4 are the narrative of the Ides of April scene, told in the clipped paragraphs Cicero reserves for political theatre: Pilius’s entrance, the reading of the two letters, the Senate’s astonishment, Cicero’s own hesitation, Sestius’s intervention, and Labeo’s clever forensic objection. Section 5 is the political climax: Cicero presses Brutus to abandon his characteristic clemency, in the sentence that has been quoted ever since — “the right place and time for clemency belong, and should belong, to other circumstances and other seasons.” What is at stake, Cicero insists, is not the persons of Antony or Dolabella but the existence of the republican order itself: nec quicquam aliud decernitur hoc bello nisi utrum simus necne. Section 6 closes with a single sentence about young Marcus, on Brutus’s staff. The register is high: it is one of the few letters in which Cicero writes a public-political doctrine to a correspondent on the equal footing of statesman to statesman.