1. He shows courage when he stands up against the mob. He is Tom Robinson's attorney, and he believes Tom is innocent. When the children show up at the event, Scout says that
"A flash of plain fear was going out of his eyes....." and "He put the newspaper down very carefully adjusting its creases with lingering fingers. They were trembling a little" (pg 152)
Atticus realized that the mob was very dangerous, but he had to protect Tom Robinson. It was one man against many others who had worked themselves into a frenzy and meant to hang Tom Robinson.
2. Atticus shows courage in the fact that he represents Tom Robinson. Miss Maudi explains to the children,
"There are some men in this world who were born to do our unpleasant jobs for us. Your father is one of them." and asks Jem, "Did it every strike you that Judge Taylor naming Atticus to defend that boy was no accident?" (pg 215)
It took someone with courage to take the job. He knew he could not win, and he knew that he could not change the racist minds of the people of Maycomb. He says,
"There's something in our world that makes men lose their heads----they couldn't be fair if they tried. In our courts, when it's a white man's word against a black man's, the white man always wins. They're ugly, but those are the facts of life." (pg 220)
3. After the trial, Bob Ewell spits in Atticus's face and threatens to kill him. Atticus does not rise to the challenge, and he tells the children
"I destroyed his last shred of credibility at that trial....The man had to have some kind of comeback...So, if spitting in my face and threatening me saved Mayella Ewell one extra beating, that's something I'll gladly take." (pg 218)
Bob Ewell also accuses Atticus of taking his job when he gets hired and fired. He upset the welfare lady so much that she told Atticus about it. Atticus just told her that
"....if Bob Ewell wanted to discuss Atticus's 'getting his job' he knew the way to his office." (pg 248)
Atticus's courage is the strong, silent type. He knows what he believes, and he stands up for what is right.