Why this play is such a standard in high school curricula is initially baffling but probably explicable:
The style of the play for the most part is one of "Roman simplicity and directness" (Wells 191) and it shows the "vanity of human ambition" (Wells 193). More compelling though, and more subtly than the simplistic peer-pressure moral, and although Shakespeare may have been "obliged" to name the play after "its highest-ranking personage" (Bloom 104), the play really focuses on Brutus and the conflict between what he believes is public good vs. his personal feelings (Goddard, I 309). Shakespeare shows the phenomenon of arguing oneself into doing something one instinctively knows is wrong -- the factors involved and the aftermath.
"To Shakespeare's original audiences, a play about ancient Rome or ancient Troy was not an escapist document about a faraway world, but something very like the opposite: a powerful lesson in modern -- that is to say, current, sixteenth-century -- ethics and statecraft" (Garber 410). E.T. Clark makes a case for the play having been first shown before the Queen at Windsor on January 6th, 1582/83 (Clark 529f) and our text being a redaction of what was originally two plays -- something like "Caesar's Tragedy" and "Caesar's Revenge" (Clark 530), two of Oxford's play combined by various of Oxford's secretaries paid by Henslowe in 1602. The assassination of Caesar allegorized the attempted assassination of the Prince of Orange (Clark 531; Ogburn and Ogburn 468-469), who had been subjected to the jealousy of the nobles around him but also had been offered the crown of the Netherlands several times and had refused it. Or, it allegorizes the murder in December 1588 of Henri, Duke of Guise, who had been the leading Catholic contender for the French throne (Anderson 239). Partisans had drawn up four pages of comparisons between Guise and Julius Caesar (Anderson 240), and odd signs were reported to have occurred in association with the assassination (Anderson 239). The play may have been "reworked" in the 1590s (Anderson 240).
Also topical in 1582 was Pope Gregory's rectifying of the "Julian" calendar, which had not been adjusted since Julius Caesar (Ogburn and Ogburn 469). "At both times there was a comet which, to the superstitious, carried portents of disaster" (Clark 532). The opening scene may reflect the situation in Antwerp, where the people took the opportunity of the birthday of the Duke of Alençon (very near the Ides of March) to celebrate a faux holiday.
More pertinent, however, I think, is Oxford's involvement in Catholicism with the Howard/Arundel group and his blowing the lid off their drifting towards an assassination plot against Elizabeth. The play exposes the tactics used to seduce one into such a conspiracy. Oxford's name appeared on a 1571 list in the Vatican archives of noblemen potentially sympathetic to the Ridolfi plot and on a later document indicating "that great interest was taken in Oxford's actions" (Pearson 105).
"Hence! home, you idle creatures, get you home! / Is this a holiday?" (I.i.1-2). The play begins on the theme of not knowing one's proper place. Two Roman tribunes, Flavius and Murellus, representative of the Roman nobility, are eager to retain the status quo of the Republic under Senate rule. They encounter workmen -- or "mechanical[s]" (I.i.3) -- and are offended by the menials' disregard for sumptuary laws: going about "without the sign / Of your profession" (I.i.4-5) or, in other words, not wearing the clothes that would designate their professions clearly. The classes are forgetting their station! The caste system is jeopardized! "Reading" itself is in danger!
The tribunes try to dissuade the forming crowds from cheering Caesar's victory over Pompey's sons. Whither their reverence for Pompey the Great? One commoner, a cobbler, uses verbal wit as a cheeky tool against the insulting tribunes. First, when asked his trade, he responds, "Truly, sir, in respect of a fine workman, I am but, as you would say, a cobbler" (I.i.10-11). Why the delicacy of phrase "as you would say"? Everyone calls a cobbler a cobbler. Does he mean to emphasize the "but" -- the tribunes' classist dismissal?
The cobbler puns on words such as "sole" and "awl," and his verbal dexterity allows him to imply that he is a priest and a doctor, of sorts. This slipperiness of language may demonstrate even more worrisome havoc to the conservative tribunes, but ultimately the populace seems easily manipulable. The two tribunes plan to remove ceremonial decorations from statues too on this feast of Lupercal (a Roman fertility celebration of mid-February), lest Caesar achieve such stature that he become a tyrant "And keep us all in servile fearfulness" (I.i.75), instead of just the mechanicals kept in servile fearfulness in accord with the current system.
So the theme established is that of not knowing one's place, of people getting uppity. Shakespeare displays through the tribunes the aristocratic view towards the masses who here, as in the Henry VI plays and elsewhere, seem to be fickle, irresponsible goobers. "The battle in Caesar's time did not really involve liberty in our modern sense. On the one hand was a time-honored but distorted and corrupt senatorial government, inefficient and dying. On the other was the one-man dictatorship of Julius Caesar, intent on fundamental reform and a centralized government.... We need not be deluded, however. The senatorial notion of 'liberty' was the liberty of a small group of venal aristocrats to plunder the state unchecked" (Asimov 260).
The celebrated Caesar, already being treated like a monarch (I.ii.1), tells his wife Calpurnia to position herself so that when Mark Antony runs the Lupercal footrace he can touch her on the way by. This is an ostensible cure for sterility, so possibly Caesar has dynastic aspirations, but mingled with sad desperation if he is this superstitious. This scene is not in the Plutarch source, and it points out that, "Like Elizabeth, Caesar was a ruler without an heir of his own body" (Garber 410). A soothsayer calls out to Caesar, "Beware the ides of March" (I.ii.18); but Caesar, who is not above speaking of himself in the third person (I.ii.17), dismisses this warning: "He is a dreamer" (I.ii.24). So Caesar is or isn't superstitious? Consensus holds that he is vain and so thinks of himself as unassailable; yet he suffers from various physical infirmities. "Shakespeare decided that his play required exactly a waning Caesar, a highly plausible mixture of grandeurs and weaknesses" (Bloom 105).
Cassius feels out a brooding Brutus, an "introspective Stoic who is fond of literature and music, considerate to people from all stations of Roman life" (Carey 88), over the Caesar question: whether he'll turn into a dictator, a tyrant. Brutus, born in 85 bce and so just past the age of 40 at this time (Asimov 263), is troubled already and declares himself "not gamesome; I do lack some part / Of that quick spirit that is in Antony" (I.ii.28-29). Cassius asks if he can see his own, presumably careworn, face. "No, Cassius; for the eye sees not itself / But by reflection, by some other things" (I.ii.52-53), replies Brutus, pinpointing the theme of the elusiveness of trying to know oneself. The real dangers are in fact internal ones (I.ii.63-65). Cassius flatters Brutus, praising his "worthiness" (I.ii.57), and he claims to be hyperselective in his friendships (I.ii.72ff). Brutus acknowledges, "I love / The name of honor more than I fear death" (I.ii.88-89). Cassius refers to Caesar's weakest moments in contrast to his apparently superior demeanor now: Caesar needed Cassius' help during a swimming contest and, in the grip of a fever, Caesar was wimpy, claims Cassius.
The fault, dear Brutus, is not in our stars,Cassius "doesn't once accuse Caesar of tyrannical behavior or of cruelty; he doesn't say his reforms are wicked or evil. He concentrates entirely on Caesar's physical weakness and poor health" (Asimov 267). Cassius also refers to Brutus' honorable ancestors and that the Roman populace therefore look to him. "Age, thou art sham'd! / Rome, thou hast lost the breed of noble bloods! (I.ii.150-151). [There's a line especially relevant to Oxford's situation in the late 1570s! Cassius' appeal to Brutus' ancestral pride (I.ii.158f) also probably echoes something autobiographical.] But Brutus is uncertain how to act.
But in ourselves, that we are underlings.
Caesar returns from the games with his groupies, including Mark Antony, who, born in 83 bce, would have been 38 years old at this time (Asimov 261). "And though he [Caesar] can be very blind, his estimate of Cassius shows him to be the best analyst of another human being in all of Shakespeare" (Bloom 106). Caesar demonstrates his good instincts when he tells Antony that "Cassius has a lean and hungry look, / He thinks too much; such men are dangerous" (I.ii.194-195). Cassius also, reportedly, doesn't enjoy plays and music (I.ii.203-204)! Resentful puritanical bastard! The elder Ogburns think Cassius represents Burghley in all this (Ogburn and Ogburn 473). Caesar proceeds onwards. "Caesar, as portrayed by Shakespeare, strikes wooden poses constantly. He is like a speaking statue, rather than a human being" (Asimov 269). Another weakness, the touch of deafness, is Shakespeare's invention.
Cassius and Brutus solicit conversation with Casca, who tells them that Mark Antony thrice offered a makeshift crown to Caesar on behalf of the crowd. It was not a crown so much as a coronet -- the headgear not for a monarch but for a count, or English earl, as Clark points out; similarly, the Prince of Orange was "offered the old title of Count of Holland," lower than sovereignty (Clark 533; cf. Ogburn and Ogburn 470).
This second-hand report is usually taken by critics as Cassius, and Casca (once he sees how to grip his audience), would like. But a real coronation by the masses at a holiday racetrack is quite illogical, Captain. Surely we can suspect it was more in the nature of a satiric game, a spectacle of dramatic gesture and good humor which Casca initially calls indeed "mere foolery" (I.ii.236) with Caesar showing what a tongue-in-cheek good sport he can be about a current goofy "issue." A "coronet" suggests a dorky prop, like a Burger King crown -- so this may all have been playful until the onset of Caesar's epilectic fit. In any case, Caesar rejected this crown and afterwards fell into an epilepsy. (Some say Caesar grew wrathful when the people failed to press the point about the crown and cheered his refusals; but we don't get this obviously dramatic scene directly, so we're at the mercy of Shakespearean ambiguity and suspect that what may have been truly public fun and "foolery" is made to seem dire by paranoid and warped minds. Here again, the people get no credit for understanding wit and satire.) Cicero also said something, but "it was Greek" to Casca, literally -- now the "proverbial protestation of failed understanding" (Garber 431). The "sour" Casca also reports that Flavius and Murellus "are put to silence" (I.ii.286). Casca hints he could tell more but ekes a dinner invitation out of it (I.ii.286ff).
Afterwards, Cassius reveals in a soliloquy his plot to rope Brutus into a conspiracy against Caesar. The conspiracy needs Brutus' moral prestige. Cassius will manufacture a mandate from the people in the form of fake notes thrown in Brutus' window. The historical Cassius married Brutus' sister and was therefore his brother-in-law (Asimov 264).
A month later, at night in the streets, Casca, who declares himself "no fleering tell-tale" (I.iii.117) even though that is all he's been so far, reports omens to Cicero: a storm, a slave's burning hand, a wandering lion, an owl hanging out at the marketplace at noon, unrest of the living dead, etc. Casca didn't seem so easily spooked in the previous scene.
Cicero agrees that "it is a strange-disposed time" (I.iii.33) but also notes that omens are often force-fit to betoken events they have no connection to (and a major theme of the play involves the ability to "read" ambiguities). Cicero leaves, whereupon Cassius enters, obsessively interpreting the signs as warnings that Caesar is a threat to the Republic and foreseeing Caesar's accession as a form of "bondage." Cinna enters and joins what is becoming a group of conspirators, and Cassius sets in motion more hoaxes that will win Brutus over to the cause. A meeting is planned with other conspirators at Pompey's Porch (a theater portico built by Pompey in 55 bce). Cassius' assertions contradict earlier ones: now the omens are "like the work we have in hand, / Most bloody, fiery, and most terrible" (I.iii.129-130). But he thinks they'll win over Brutus: "Three parts of him / Is ours already, and the man entire / Upon the next encounter yields him ours" (I.iii.154-156).