Why does Shakespeare include the ghost of Caesar in Julius Caesar? What is he trying to tell the audience?

Explain the effect of the rhetorical questins for the below paragraph."i pinched myself: was i still alive? was i awake? how was it possible that men, women, and children were beiing burned and that the world kept silent? no. all this could not be real. a nightmare soon i would wake up with a start, my heart pounding, and find that i waas back in the room of my childhood, with my "