Throughout the entire trial of poor, innocent, "mockingbird" Tom Robinson, Atticus Finch essays to cure Maycomb of its "usual disease." For, after his daughter Scout has won a small victory against the mob at the jail when she touches the conscience of Mr. Cunningham, Atticus feels that there exists the chance, the small chance, of awakening in the jury a social conscientiousness.
Atticus affirms at the end of Chapter 20 that he is not idealist who believes in the integrity of the courts in America, because
"a court is no better than each man of you sitting before me on this jury. A court is only as sound as its jury, and a jury is only as sound as the men who make it up. I am confident that you gentlemen will review without passion the evidence you have heard, come to a decision, and restore this defendant to his family. In the name of God, do your duty."
Knowing that Mr. Cunningham, an uneducated man from the country has been capable of reasoning without allowing his prejudices to interfere, Atticus builds upon this confidence in Mr. Cunningham. Thus, he appeals to the conscience and the reason of the members of the jury, hoping that others will feel the prick of their consciences,too.
"Our courts have their faults, as does any human institution, but in this country our courts are the great levelers, and in our courts all men are created equal."
Here Atticus is trying to remind the jury that the jurors are responsible to put aside prejudice and listen carefully and objectively to the evidence because Tom Robinson, as well as any other American, deserves a fair trial. Atticus knows that this will likely fall on deaf ears; he is more than aware that the odds of Tom Robinson getting a fair trial are slim to none, but he gives 100% anyway, and works as hard for Tom Robinson as he would any other client.