Fates, we will know your pleasures: / That we shall die, we know; 'tis but the time / And drawing days out, that men stand upon. Cassius is worried that friends of Caesar might attack, and people are running about as though "it were doomsday," but Brutus is not afraid of death. He knows that he will die (because all people die); he (like everyone else) only wonders just when he will die, and how long he has before it happens. If death comes to him, it will be something that happens at the pleasure of the Fates, not a punishment for killing Caesar.