William Lloyd Garrison, who was the editor of the abolitionist newspaper The Liberator, wrote the Preface to the Narrative of the Life of Frederick Douglass to vouch for Douglass's veracity. Some people at the time doubted that Douglass, a former slave, could have written such an eloquent autobiography, so Garrison was supposed to assure the public that Douglass was truly the author of the narrative. It was a sign of the racism of the era that Douglass needed a white man to vouch for him.
In the Preface, Garrison recalls having seen Douglass give a speech at an anti-slavery conference in Nantucket in 1841. Garrison says that Douglass's speech received great applause. He writes that what made Douglass such a powerful speaker was the discrepancy between his incredible intellect, eloquence, and morality on one hand and his degradation as a fugitive slave on the other. Garrison writes of Douglass that he is "Capable of high attainments as an intellectual and moral being [but] by the law of the land, by the voice of the people, by the terms of the slave code, he was only a piece of property, a beast of burden, a chattel personal, nevertheless!" In other words, Douglass shows that slavery can degrade a person who is capable of great achievement and who has superior intellect and morality. Garrison says that Douglass's speech made him hate slavery more than he ever had in his long career as an abolitionist.