Why do authors use rhetorical devices in essays? (plato answer)

Which quote from act one scene three in the tragedy of julius caesar is the best example of foreshadowing a. why all these fires, why all these gliding ghosts, why birds and bees from quality and kind why old man, fools, and children calculate b. that heaven hath infused them with these spirits to make them instruments of fear and warning unti some monstrous state c. it is the part of men to fear and tremble, when the most mighty gods buy tokens send such dreadful heralds to astonish us d. oh he sits high in all the peoples hearts, and that which would appear offense in us his countenance, like richest alchemy, will change to virtue and worthiness