In act 5, scene 1, lines 73–88 of William Shakespeare’s Julius Caesar, Cassius discusses with Messala about the battle they will fight later that day. The armies that he and Brutus command will meet up with Antony and Octavius’s forces. The conversation with Messala directly follows a meeting among the four generals, in which Octavius vowed to avenge Caesar’s murder.

Mentioning that today is his birthday, Cassius shares with Messala his reluctance to fight on this day because he has observed some bad omens. Formerly, he did not believe in such omens, but he has changed his mind. In presenting this altered opinion, Cassius refers in lines 83–85 to Epicurus:

You know that I held Epicurus strong,

And his opinion. Now I change my mind,

And partly credit things that do presage.

Epicurus was a Greek philosopher who lived from 341 to 270 BCE. Overall, he advocated for a rational, empirically based understanding of life and for rejecting superstition. One of his claims was that the gods did not influence or control human lives, and so there was no reason for humans to fear them.

Cassius now partially believes that the “things … [he has seen] presage” their defeat in battle. The specific signs that he mentions are birds. Earlier he had seen eagles calmly eating out of the soldiers’ hands, which was a good sign, but they have flown away. The birds that now fly over their camp—“ravens, crows, and kites”—look at the men as if they “were sickly prey.” Cassius sees the birds as a dark canopy that indicates the deaths of their troops.