What is the main conflict in This Fiery Trial: The Speeches and Writings of Abraham Lincoln by Abraham Lincoln?

This Fiery Trial is a collection of the speeches and writings of Abraham Lincoln, as selected and edited by William E. Gienapp. They span the entirety of Lincoln's public service career, from 1832 when Lincoln was considering public office in Sangamo County, to April 11, 1865, three days before Lincoln was assassinated.