This makes sense provided astrology in general does.
Caesar does not go so far as to scorn astrology, but he does scorn fear in a pair of famous lines:
—Act II, scene ii, lines 32-33
Nevertheless, Calphurnia continues to beg and eventually Caesar is sufficiently swayed to grant her her wish and to agree to send Mark Antony in his place.
It is morning by now, however, and Decius comes to escort Caesar to the Capitol. The news that Caesar has changed his mind and will not come staggers him. Quickly, he reinterprets all the omens and hints the senators will laugh. Not only does he make use of the threat of ridicule, but he also says:
—Act II, scene ii, lines 93-96
This seems true enough. Caesar is trying to pull off a coup that runs counter to the deepest Roman prejudices and it was bound to be a near thing. He had failed, at the Lupercalian festival, to gain a crown by popular acclamation. If he now missed a chance to force the Senate to give him one, he would be giving his opponents a chance to mobilize their forces and the whole project might be ruined. The historic Caesar won many successes by striking when the iron was hot and it isn't likely that he would let such a crucial moment pass.
Caesar changes his mind once again and makes the fateful decision to go.
Caesar's progress toward the Capitol is attended by further warnings, according to Plutarch's story, which Shakespeare follows. The soothsayer is there and Caesar tells him ironically that the ides of March are come (presumably implying that all is well). To which the soothsayer answers, portentously:
—Act III, scene i, line 2
Another man, Artemidorus, attempts to give Caesar a warning. According to Plutarch, he was a Greek professor of rhetoric from whom a number of the conspirators had been taking lessons. (In those days, rhetoric, the art of oratory, was indispensable to a public career.) He had picked up knowledge of their plans, presumably because they spoke carelessly before him, and he was anxious to reveal those plans to Caesar (perhaps out of pro-Caesarian conviction or perhaps out of the hope of profiting by Caesar's gratitude).
In any case, he passes a note of warning to Caesar, telling him of the plot. According to Plutarch, Caesar tried several times to read the note but was prevented from doing so by the press of people about him. Shakespeare makes it more dramatic, showing Caesar, by his arrogance, bringing his fate upon himself.
Artemidorus, in an agony of Impatience, cries out, as other petitions are handed Caesar:
—Act III, scene i, lines 6-7
But Caesar answers grandly:
—Act III, scene i, line 8
And thus he condemns himself.
In what follows, Shakespeare follows Plutarch very closely. The conspirators crowd around Caesar on the pretext that they are petitioning for the recall of the banished Publius Cimber, the brother of Metellus Cimber. Caesar refuses, in a fine oratorical display of unyieldingness, saying:
—Act III, scene i, lines 60-62
The Northern Star (Polaris) does not itself move. Rather, all the other stars circle about it as a hub (in reflection, actually, of the earth's rotation about its axis, the northern end of which points nearly at Polaris). Caesar's picture of himself as the unchanging Northern Star about which all other men revolve is an example of what the Greeks called hubris ("overweening arrogance") and it is followed quickly by what the Greeks called ate ("retribution"). It is the biblical "Pride goeth before… a fall."
The conspirators have now surrounded him so that the onlookers cannot see what is happening, as each approaches on pretense of adding his own pleas to the petition. When Brutus makes his plea, Caesar is embarrassed. The Dictator has repulsed Metellus Cimber haughtily but he cannot use similar language to the beloved Brutus. All he can say is an uneasy:
—Act III, scene i, line 54
Then, later, when Decius begins his plea, Caesar points out that he cannot do it even for Brutus, saying:
—Act III, scene i, line 75
At which point Casca strikes with his dagger, crying:
—Act III, scene i, line 76
According to Plutarch, they each proceed to strike at Caesar, having made an agreement among themselves that each conspirator must be equally involved in the assassination. No one of them must be able to try to escape at the expense of the others by pleading he did not actually stab Caesar.
Caesar tried vainly to avoid the blows until it was Brutus' turn. Brutus, according to Plutarch, struck him "in the privities." That was the last straw for Caesar. When Brutus lifted his weapon to strike, Caesar cried out, "Thou also, Brutus!" and attempted no further to avoid the strokes. His outcry, in Latin, was so famous that Shakespeare made no attempt to translate it, but kept it as it was, a small patch of Latin in the midst of the play:
—Act III, scene i, line 77
So died Julius Caesar, on March 15, 44 b.c., hacked to death by twenty-three stabs. Brutus had earlier made an apparently noble speech to the effect that they not "hack the limbs" and that they "be sacrificers, but not butchers" (see page I-279). He had meant it figuratively with reference to the possible death of Mark Antony, but now that speech takes on a grislier aspect, when it turns out that Caesar has, deliberately, been hacked and butchered to death.