Afew ideas for your essay might be to focus on Atticus' courage in taking Tom's case.... the courage that comes from knowing you're doing the right thing.
As far as faith, Atticus never loses his faith in humanity.... he truly believes that there are people listening.... that maybe, just maybe, the jurors will see the truth rather than the color of a man's skin.
Lastly, we have conscience. Throughout the novel, Atticus models appropriate behavior for his children. He will not act in a way that fails to teach them right and wrong. His conscience leads him to show his children the right way, to act in a way that he himself can be proud of.