What does Atticus mean when he says, "Don't fool yourselves--it's all adding up and one of these days we're going to pay the bill for it"?
Atticus and Jem are discussing the Tom Robinson case in chapter 23, which involves juries, capital punishment, and the justice system in Alabama and in the United States. Atticus teaches Jem that he is not against rape being a crime worthy of capital punishment in Alabama, but he is against convicting someone of it based on incomplete and inaccurate evidence. He's also upset about Tom Robinson's conviction because it was based on prejudice and discrimination rather than truth. As a result, Atticus says the following:
"There's nothing more sickening to me than a low-grade white man who'll take advantage of a Negro's ignorance. Don't fool yourselves--it's all adding up and one of these days we're going to pay the bill for it. I hope it's not in you children's time" (221).
Atticus is saying that for hundreds of years in the South white men have taken advantage of black people and one day there will be a price to pay for it. The South already paid for slavery by fighting and losing The Civil War; it's only a matter of time before the South will pay again for the discrimination and prejudice used against blacks after that war. The year is 1935 when Atticus says this--less than thirty years before the Civil Rights movement of the 1960s. What he says is prophetic because the South is eventually forced to desegregate and play straight. Fortunately, there wasn't a second civil war, but many people lost their lives fighting for the Bob Ewells of the world to stop winning based on prejudice, and for African Americans to be treated fairly in court, in school, and in the voting booths. Atticus wants his son to know that the way things are at that point in 1935 won't be the way it is forever; and that one day the bubble will burst, but he hopes that it won't be so bad as to hurt his children in the end.
This can be found in Chapter 23. Atticus speaks these words after the Tom Robinson trial has ended and Tom has been convicted.
What Atticus says is that black people have been abused (like Tom Robinson has been) for too long. He says that the frustrations of the blacks are adding up and that there will be a rebellion some day. That is what he means by saying that one day they will have to pay the bill.
He hopes that the bill will not need to be paid in his kids' lifetime, but he says that eventually it will have to be paid.