In the Letter to Birmingham by Martin Luther King, Jr. the most vivid form of appeal that he tries to persuade his audience with is emotion. Throughout the letter he wants to grab the white and black citizens not only in Birmingham, but around the nation and show them his viewpoints. In his letter he wants to show white citizens that it's time for blacks to be considered equal as whites. Dr. King uses frequently biblical passages in order to get some emotion out of the readers. Whenever someone uses a biblical passage it evokes some kind of emotion into the reader. I believe he uses the biblical passages to show whites how Jesus didn't dislike someone becuase of the color of their skin.
Another thing that Dr.King uses in his letter is his frustration. In the beginning of the letter he starts off calm, but towards the middle and end his tone turns into frustration and disappoinment. By his tone you can tell that he is at his end and he knows something needs to change know. He also, sounds tired and he knows that his time is almost complete. By him using frustration in his tone I draws the reader in and makes them want to take action.