It is Cassius' cleverness that comes to the fore now. In order to convince Casca of the worth of his cause, Cassius does just as Cicero, the great orator, has suggested men would — he interprets and manipulates the omens for his own purposes. In his hands, all of these frightening events are happening because the heavens "hath infus'd them with these spirits, / To make them instruments of fear and warning / Unto some monstrous state." The monstrous state, Casca is meant to believe, is Caesar's Rome. Cassius tells Casca that there is a man who is "most like this dreadful night, / That thunders, lightens, opens graves, and roars / As doth the lion in the Capitol." Casca asks directly if Cassius means Caesar but, not wanting to reveal himself too quickly and not wanting to leave the possibility open that his words could be turned against him, Cassius allows Casca to draw his own conclusions. Having established the problem, Cassius comes up with a solution. He points out that Caesar is just a man, not a god, and that all of these terrible visions can be overcome by a true, idealized Roman who calls on the spirits of his ancestors for strength and perseverance. Once again, Cassius has found the best way to persuade his listener — in this case, he has called on Casca's image of himself as a noble and loyal Roman, and given him an opportunity to act on it.
Casca joins the plot and the conspirators' faction is enlarged, but to be successful, the person they really need is Brutus. Brutus is well-regarded, wields a great deal of power and, after Caesar is overthrown, has the strength to manage that chaotic and potentially dangerous group, the people. "O, he sits high in all the people's hearts; / And that which would appear offence in us, / His countenance, like richest alchymy, / Will change to virtue and to worthiness." Act I ends in gloom and darkness with the state beginning to splinter. The daylight that Cassius perceives on the horizon is, paradoxically, a light that will show the cracks all the more clearly.
