There’s a fateful moment early in Julius Caesar when Brutus, in soliloquy, decides Caesar must be killed:

It must be by his death: and for my part
I know no personal cause to spurn at him
But for the general. He would be crowned:
How that might change his nature, there’s the question.
It is the bright day that brings forth the adder,
And that craves wary walking. Crown him that,
And then I grant we put a sting in him
That at his will he may do danger with. (2.1.10-17; Arden edition)

The first phrase is firm but unclear. What is the antecedent of “It”? We know “his” refers to Caesar, but Brutus doesn’t name him. “Must”: that is, to be obliged to; compelled, commanded, required.

“It must be by his death”: this might seem a line that would conclude a soliloquy such as this, but Shakespeare puts it at the beginning. Brutus isn’t thinking toward a conclusion. He has reached it already, and the thinking he now does follows from it.

We hear the implication of role-playing and performance in “my part,” which Shakespeare accents by locating the word with the iambic pentameter stress at the end of the line. We pick up, too, Brutus’s admission that he has no “personal” charge or accusation to make against Caesar, only a “general” one.

There’s also the strong verb “spurn,” which means to strike, tread, or push away with the foot, to reject with disdain or contempt. It’s given further force in the 1623 First Folio (F) text, which inserts a comma after “cause,” calling for a hesitation that encourages the voice to actuate the discharge in “spurn.”

“He would be crowned” is ambiguous. It’s something that might happen to Caesar or that (with volition) he seeks to make happen himself. “Bright day” is hopeful, but only for an instant, and then the adder appears, the viper, a venomous snake. In F, “adder” is capitalized, looming even larger. The metrical stress falls on “that” to clinch the connection: “And that craves wary walking.”

“Craves,” not stressed, is followed by the tentative and cautious “wary.” The alliteration in “wary walking” intimates how vigilant we must be to evade peril. “Wary” evokes the need for watchfulness, and in the theater, when we hear the word rather than read it, it may convey weariness, wary/weary, the tiredness coming from lack of sleep, for Brutus has been kept awake by his night-time ruminations.

Shakespeare could have moved from “He would be crowned” to “Crown him that.” But he wants the “adder” image to show Brutus picturing a threat that’s familiar to him, one he knows is there and that, visualized, he reminds himself about. With the meter putting a stress on “sting,” this image reassures Brutus that his brooding is to the point, for there’s a toxic presence in the world he and we must guard against.

If “he” is crowned, we’ll be obliged to acknowledge that we have inserted the sting, injected the poison, made the menace. The bind Brutus finds himself in is that he can’t identify any crimes and abuses of power the adder has perpetrated. The indictment Brutus prepares can only be based on speculation about the future, not on the present:

Th’ abuse of greatness is when it disjoins
Remorse from power; and to speak truth of Caesar
I have not known when his affections swayed
More than his reason. But ’tis a common proof
That lowliness is young ambition’s ladder
Whereto the climber upward turns his face;
But when he once attains the upmost round
He then unto the ladder turns his back,
Looks in the clouds, scorning the base degrees
By which he did ascend. So Caesar may.
Then, lest he may, prevent. (2.1.18-28)

Brutus can’t be certain that Caesar will misapply power. This might occur; it might not. The counterforce, meanwhile, is in the word “prevent,” with the stress on the second syllable made robust by the period, the pause in the middle of the line.

“Prevent” is late Middle English, “act in anticipation of”; from the Latin praevent, “preceded, hindered,” from the verb praevenire, prae “before” + venire “come.” Renaissance punctuation is loose, not stable, but for “prevent” to receive the emphasis it should, I prefer the F printing: “So Caesar may; / Then lest he may, prevent.” The semi-colon after the first “may” is a bit more open than a full-stop period. There’s no comma in F after “Then,” which gives the phrase a flow that “prevent” halts.

Shakespeare could have ended with “prevent.” Brutus has said all he needs to justify the action he plans to take. But Shakespeare starts a new sentence with the conjunction “And,” as if the previous sentence, which seemed stopped by the period, were still in motion:

And since the quarrel
Will bear no color for the thing he is,
Fashion it thus: that what he is, augmented,
Would run to these and these extremities.
And therefore think him as a serpent’s egg
Which hatched, would as his kind grow mischievous,
And kill him in the shell. (2.1.29-35)

Some scholars have rebuked Brutus for failing to comprehend what he’s saying. They maintain he’s self-deceived, unaware he’s seeking to justify a choice he has already made, the decision he started with. There’s no “we must” or “we will” or “I must and will” in Brutus’s closing line. “Kill him” could not be more deadly and purposeful, but the killing is without an agent, not assigned to anyone.

Caesar must be assassinated. This is the non-negotiable element of the story that Shakespeare is dramatizing; he can’t show Brutus renouncing the murder plot. Yet it’s more than that: this is Brutus thinking in a form that may be fault-ridden but that’s also all-too-human. On issues both serious and slight, most of us have thought at times as he does. We decided to do something, and we then searched for and seized on arguments, plausible phrases, and expedient images to rationalize it.

Shakespeare could have given us an earlier soliloquy where we would witness Brutus’s decision being made. We’d see the moment of choice, the thinking that preceded the thinking that Brutus now does when he says, “Yes, as I have already decided: it must be by his death, and here are the reasons why.”

What led Brutus to decide to kill Caesar? He feels he must; he knows he will. He has already decided to make the decision he announces here: the argument comes after it, in a way as an after-thought. Shakespeare understands that decisions are often a leap of faith. We judge them retrospectively, by their consequences.

William E. Cain is Mary Jewett Gaiser Professor of English at Wellesley College, where he enjoys teaching courses on Ralph Waldo Emerson, Henry David Thoreau, and other American writers. His recent publications include essays on Edith Wharton and Ernest Hemingway.