American history is a contentious subject, familiar terrain for culture wars that dispute the meaning of the past and what it says about the nature of our country. Who gets to write our history? How should it be written? What do we accept as evidence? Which historical voices should be deemed legitimate? These questions are particularly fraught when one is dealing with past atrocities, like America’s racially based system of chattel slavery. Guilt, denial, shame, anger, and fear are just a few of the emotions that permeate discussions of the topic, as the legacies of slavery continue to shape the race relations and political structure of our nation.

Then there is history’s cruel irony: the individuals who bore the brunt of the system—the enslaved—lived under a shroud of enforced anonymity. The vast majority could neither read nor write, and they therefore left behind no documents, which are lifeblood of the historian’s craft. The voices that we would most like to hear—the voices that we most need to hear—are silent. This is why the narratives of the relatively few enslaved people who managed to tell their story loom large: Olaudah Equiano, in the eighteenth century, and Henry Bibb, Frederick Douglass, Harriet Jacobs, and Solomon Northup, in the nineteenth century.

Northup’s narrative, “Twelve Years a Slave,” which the director Steve McQueen has brought to life on the big screen, to stunning effect, vividly conveys the realities of life within the peculiar institution. Northup’s story deviates from the typical narrative in which the slave gains freedom and then tells his or her story. He was a New Yorker who went from freedom to slavery after being abducted in 1841 and sold down the river, in Louisiana. Readers of the narrative and viewers of the film, as free people, can immediately understand what Northup, a cultured man who made his living as a violinist, lost. Northup eventually regained his freedom and, with the keen eye of an outsider, shared his intimate view of the day-to-day workings of a plantation in the Deep South.

As powerful as they are, slave narratives are often said to raise special concerns as items of historical evidence. One argument goes as follows: White abolitionists, who almost always had a hand in helping to prepare and disseminate the narratives, hoped to destroy slavery by highlighting the more shocking aspects of the institution—the whippings, the separations of families, and the sexual abuse of enslaved women. As a result, the argument continues, the narratives adhere to a literary convention in which all of these events must play a prominent role, raising questions about the veracity of the stories. This seems a rather odd complaint, given that we know from other sources that whippings, separation of families, and sexual abuse were endemic to the institution. It would be more incredible, quite frankly, if Solomon Northup had spent twelve years on a slave plantation in Louisiana without encountering all of these things.

Another concern centers on the nature of the relationship between white sponsors and black narrators. Given the racial power dynamics, could blacks speak freely to the abolitionists and, later, to the white interlocutors who gathered stories for the Work Project Administration (W.P.A.), during the nineteen-thirties? If points of conflict arose, whose view would prevail? It has also been noted that the W.P.A. interviewees were children during slavery. A number of them painted almost benign pictures of the institution of slavery. Was this done to please their white interviewers, who were, after all, agents of the government, or were they just remembering a world through the eyes of children, without the heavy burdens that their parents had known?

There are other issues with slave narratives, but the simple fact is that every form of historical evidence has its own set of problems. The historian’s task is to recognize this truth, figure out what problems are inherent to each form of evidence, and find ways, if possible, to surmount them. Take that most cherished of historical documents, the family letter. Letter writers often used the medium to create a pictures of what their families were like, and to illustrate what role they played in the family. Sometimes the picture was good. Sometimes it was bad. But the family letter is always subjective, and carries with it the problems that go along with all subjective judgments. We must be wary of them—not reject them out of hand but, rather, recognize their limitations.

What do we do to satisfy ourselves that any critical or important information contained in a family letter, or in any letter, is reliable? We look for evidence outside of the document, preferably created by someone other than the letter writer, to support what it says. If the letter presents information that we have no good reason to question—if the writer is not saying anything that is fantastical, or which contradicts other known information—we tend to accept its assertions. There is only so much time in the day and in life. The same process can be, and has been, followed with slave narratives. As a result, one important aspect of Equiano’s narrative—that he was born in Africa—has been called into question. On the other hand, important aspects of Northup’s narrative have been confirmed.

Another problem hovers over the slave narrative as a literary genre: the role that race and status played in the reception of stories told by members of a disfavored—or despised—racial group. It is one thing for a Solomon Northup to speak about individuals who are, in historical terms, unimportant in order to indict a system that most people recognize as abhorrent. It is another thing when a narrative presents information that many whites might not wish to hear or to accept.

I wrote an entire book about this issue, “Thomas Jefferson and Sally Hemings: An American Controversy,” examining in minute detail one historical controversy as it plays out in family letters and slave narratives. There was, I found, a double standard in the treatment of the recollections of a powerful slave-holding family, which were memorialized in their personal letters, and those of the people enslaved on their plantation, which were given to an interviewer. It would have been a simple matter to recognize the unique concerns raised by each item of evidence and then research around the dispute to determine which version was more likely. Instead, the power that the letter writers had in life, and the relative powerlessness of those who gave the interviews, was simply reconstituted in the pages of history.

With that said, the writing that has been done in the past sixty years on slavery is, I believe, the crown jewel of American historiography. But as much good work as has been done, there is even more to do. It will be wonderful if “12 Years a Slave” not only introduces millions to Solomon Northup but propels them into libraries and bookstores to read the stories that have been told about the institution that haunts us to this day.

Annette Gordon-Reed, is a professor at Harvard University and the author of “Thomas Jefferson and Sally Hemings: An American Controversy” and “The Hemingses of Monticello: An American Family.”

Photograph courtesy of Fox Searchlight.