History is given to us. We are born in a given time, and place. We can, though, change our personal , and social consciousness. If we do not, nothing will. That is the purpose, and meaning of life. We are here to construct the Universe's Consciousness. Lincoln tells his inner circle, the time is now, we must pass the Thirteenth Amendment in our time.
The movie tells the story of Lincoln, and his family, at the same time tells the story of the Civil War. For me the most poignant moment was Thaddeus Stevens Speech defending the Amendment. He was taunted by his adversaries to come in defense of African Americans in court, instead he chose to attack their character.
People like Lincoln and Stevens, constructed the Social Consciousness of the United States of America (USA). This process will only end when the USA cease to exist.