Growing up on the rough-and-tumble western frontier, Abraham Lincoln's youth was a masterclass in the value of hard work. Yet as he ascended the ranks of society from unschooled farmer to lawyer to president, he was acutely aware that much of his success was due to the American commitment to ensuring that people from all backgrounds had the opportunity to advance. Holzer and Garfinkle argue that Lincoln's guiding principle for entering the Civil war was a commitment to defending equality of economic opportunity for all Americans rather than the eradication of slavery or the defense of the Union.