Brutus, unable to sleep, paces in his orchard. He talks to himself, reasoning that he has nothing against Caesar personally. However, kingship might change Caesar, leading him to abuse his power. Caesar, then, should be regarded as a “serpent’s egg” that must be crushed before it has the chance to hatch.
Ironically, Brutus is the first character in the play to explicitly state that Caesar must be killed. Unlike the other conspirators, he isn’t concerned about the personal repercussions of the act, but about whether killing Caesar is the right thing to do for Rome.
Lucius, a servant, brings Brutus a letter he found on the windowsill. Brutus reads the letter by the light of whizzing meteors. It says, “Awake, and see thyself! Shall Rome, etc. Speak, strike, redress!” Brutus interprets this to mean that he, like his ancestors who drove out the Tarquin, should act to prevent Rome from falling under the sway of a king.
Meteors, even in Shakespeare’s time, were believed to herald important events. By Cassius’s design, the letter contains gaps which Brutus fills in—without his supplied interpretation, it would be meaningless. The “Tarquin” refers to Lucius Tarquinius Superbus, the final king of Rome, whose overthrow in 509 B.C.E. led to the establishment of the Republic.
Brutus has asked Lucius to confirm the date; Lucius checks the calendar and says that it is indeed the 15th of March. As Lucius answers a knock at the door, Brutus reflects that he hasn’t slept since Cassius spoke to him of the conspiracy. While anticipating the assassination, Brutus feels as though there is a rebellion in the “little kingdom” of his body.
The “ides of March,” the day that the soothsayer warned Caesar about, has come. The unsettled state of Brutus’s body and mind, brought on by a crisis of conscience, symbolizes the restless state of Rome at large.
Cassius has arrived, and Lucius reports that he is accompanied by others who are concealed in their cloaks. As Lucius lets the group in, Brutus reflects on the “monstrous” nature of conspiracy. When Cassius comes in, he introduces the other conspirators: Trebonius, Decius, Casca, Cinna, and Metellus. Brutus shakes hands with them, but when Cassius proposes an oath, Brutus objects that the corruption of the times should be motivation enough to follow through on their plot, and that Romans should be able to trust one another’s word.
Brutus’s commitment to killing Caesar is motivated by his sense of moral duty, so he is disturbed by the secretive, underhanded behavior of his co-conspirators—hence his rejection of an oath.
Cassius suggests that Cicero be included in the plot, and the others agree, Metellus pointing out that Cicero’s age and rhetorical skill will win others to the cause. Brutus rejects this idea, saying that Cicero isn’t a follower.
Cicero was one of the most revered, eloquent orators in the history of Rome, so the conspirators’ desire to use his influence makes sense. However, Brutus’s objection, along with his previous rejection of an oath, shows that he’s emerging as a leader of the conspirators. It also further illustrates his commitment to principle rather than mere populism.
Cassius suggests that Mark Antony be killed as well, since he’s so close to Caesar. Again, Brutus objects, arguing that they must be “sacrificers, but not butchers.” They must kill Caesar “boldly, but not wrathfully.” Anyway, he concludes, Antony will be powerless—like a limb without a head—once Caesar is dead.
In a heavily consequential decision, Brutus rejects the idea of murdering Mark Antony on the grounds that it’s motivated not by duty to Rome (like their murder of Caesar), but by blind wrath and bloodthirst. Ironically, his insistence on moral restraint will lead to his own death.
The clock strikes three. Cassius says that it’s doubtful whether Caesar will go to the Capitol today—he’s grown so superstitious lately. Decius offers to make sure Caesar goes. They discuss bringing Caius Ligarius into the conspiracy, and Brutus says he will take care of this. The conspirators part for the night.
The striking of a mechanical clock is an anachronism, as such clocks didn’t exist in ancient Rome. Shakespeare likely included this detail not only to give the audience a sense of pacing and immediacy, but to make the action seem more in sync with to the contemporary time period when the play was performed. The conspirators’ plans go forward, albeit amid much uncertainty—will Decius’s and Brutus’s errands succeed? The outcome seems to rest on more than abstract Fate.
Portia enters, asking Brutus about his strange behavior lately—he’s been so restless and distracted. She pleads with Brutus to tell her what is bothering him and who the visitors were. She says that although she is a woman, she is Cato’s daughter and Brutus’s wife, and therefore she is stronger than women in general. In fact, she has wounded herself in the thigh to prove her strength and loyalty. There is a knock at the door, so Brutus promises he will unburden his thoughts to her later.
Portia’s speech uses logic to prove her trustworthiness. She uses her relationships to noblemen—her father (the Roman statesman Cato) and Brutus himself—to demonstrate her strength, taking for granted the contemporary belief in women’s weakness. Her self-injury shows that “masculine” strength was associated with self-sacrifice and the ability to withstand violence and pain.
Caius Ligarius enters. He is sick but eager to be involved in the plot—“a piece of work that will make sick men whole.” He and Brutus set off together in Caesar’s direction, the sound of thunder in the background.
The metaphor of bodily sickness symbolizes the illness of Rome itself; killing Caesar will “heal” the body politic. Thunder continues to be a portent of the ominous deed to come.