In this section, we see that Bob Ewell has become threatening, and that he has attacked Atticus. As Atticus was leaving the post office, Bobe Ewell approached him, spat on him and cursed him. However, we learn that Atticus is not scared. In fact, Atticus explains that Ewell has lost all credibility due to Atticus, and he wants to take revenge. Moreover, he tries to think of the type of person Ewell is, and what he might be thinking he can do in order to save face. This shows that Atticus is very empathetic, and is also very good at understanding other people's feelings and motivations.
