Atticus believes that all people are created equal and the justice system should treat them that way.
In his closing arguments, Atticus reminds the jury that the Declaration of Independence says that all men are created equal, and in a courtroom it is their duty to uphold that.
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 … and restore this defendant to his family. (ch 20)
Atticus asks the jury to believe Tom. He knows that they will have a difficult time taking the word of a black man over the word of a white woman. This is because in Maycomb, blacks and whites are not treated the same. Yet Atticus hopes that they will see the responsibility as a jury.
Unfortunately, they don't. The convict Tom, but they do deliberate longer than anyone thought they would. Atticus made some progress. He got them to imagine the world a different way, and consider for a moment what was right.