Shakespeare, like all writers, wants to use images and figures of speech that all readers can relate to. If a writer uses images and figures of speech that readers don’t fully understand their meaning will be lost. Consider the following metaphor.
Vexed I am
Of late with passions of some difference,
Conceptions only proper to myself,
Which give some soil perhaps to my behaviors;
This is Brutus speaking to Cassius in Act I, Scene 2. Prior to this, Cassius had asked Brutus why he seemed so distant lately. Brutus is trying to explain to Cassius that he just has something on his mind that is important. The metaphor and image is created with the word “soil.” When Brutus says that his “conceptions give some soil . . . to my behaviors,” he is using a natural (in the sense that soil is something from nature) image/metaphor to express the idea that his behavior is “growing” in soil created by his ideas (conceptions). This image/metaphor would have been easy for his audience to understand. Therefore, he successfully established Brutus’ state of mind early in the play.