Respuesta :
He is saying along the lines of that the north doesn't enslave but the south does angering the blacks wanting to free themselves.
In this passage, the theme, or the main idea of the text is that slavery caused the Civil War.
In these lines, we learn that Lincoln believes "all knew that this interest was somehow the cause of the war." In other words, everyone knew that the war had started because of the issue of slavery. He tells us that the South wanted slavery to spread to other states, while the North wanted to limit this. Their disagreement eventually led to the war, and the conflict became so big that slavery ended before the conflict could be solved.