Frederick Douglass – runaway slave, radical activist, brilliant orator and writer, tireless advocate for his race, political office-holder – lays claim to being the most influential African-American of all time. Certainly, no other black American life has been more remarkable or significant, and few other lives, black or white, have lent themselves, as did Douglass’s, to the publication of three separate and bestselling autobiographies, each of them an essential source for a biographer. In his mid-twenties, newly established as an abolitionist celebrity, he wrote Narrative of the Life of Frederick Douglass, a dramatic account in simple but vivid prose of his twenty years as a Maryland slave; further autobiographies, published in 1855 and 1881, stylishly recorded his activities as a campaigner for emancipation and racial equality both during the civil war that secured black freedom and in its aftermath, when the halting steps towards black civil rights faltered.

Douglass was born Frederick Augustus Washington Bailey. After escaping to freedom in 1838 he took the name by which he would achieve national and international fame, an act of self-creation inspired by Walter Scott’s poem Lady of the Lake. It was just one metamorphosis in a life of dramatic transformations. Slaves were denied education, yet Douglass would win a reputation as a literary genius. The physical courage he demonstrated as a young man – in a celebrated fight with a professional slave-breaker, confrontations with white workers in the Baltimore shipyard and escape from bondage – gave way to intellectual power; radical thought, gifted oratory and campaigning journalism became his characteristic weapons. Lacking a close-knit family as a boy – separated from his mother and unsure of his white father’s identity, he called himself a ‘wounded soul’ – he became the patriarch of a vast, dependent and often troubling family of sons, daughters and grandchildren. Subjected to cruelty by Southern Christians, he would satirise those who invoked the Bible to justify slavery and found personal and political meaning not by rejecting religious faith but by immersing himself in the Scriptures. Douglass the radical outsider, an admirer of the insurrectionist John Brown, after the Civil War became a Republican Party insider, serving in political and diplomatic posts. After the death of his wife of forty-four years, Anna, a freeborn but illiterate black woman, he shocked the conventions of his age by marrying Helen Pitts, a well-educated white activist schooled in abolitionism and women’s rights. In later life, he put aside the bitterness he felt for his former owner, Hugh Auld, and reached out to his family; remarkably, among the altar display at Douglass’s funeral were flowers sent by the Aulds.

Douglass has not lacked sympathetic biographers, but none has served his subject with such authority and eloquence as David Blight in this Pulitzer Prize-winning study. A major challenge is to get behind the self-made public hero of the autobiographies and pin down the private man. Blight handles with great sensitivity the tensions between the two sides of his life. The precise nature of the strains placed on Anna Douglass, not least by her husband’s absences on his Herculean speaking tours, has to remain a matter of intelligent speculation. There is, though, no doubt of the important friendships and lasting intellectual companionship that Douglass developed with white women, including Julia Griffiths, a radical English abolitionist who crossed the Atlantic to manage his publishing and business affairs for several years, and Ottilie Assing, a feminist and German immigrant who translated his works for a German audience, lived in his home for long periods and possibly entered into an emotionally intimate relationship with him.

During their twenty-eight-year friendship, the freethinking Assing tried unsuccessfully to convert Douglass to atheism, her hopes no doubt raised by his lifelong scorn for white supremacists’ religious hypocrisy. But she failed to understand how much her hero’s understanding of the world was coloured by his belief in God’s intervention in history. The narrative of Exodus, the warnings of Jeremiah and the wisdom of Isaiah fundamentally shaped his personal and political creed, to a greater extent even than the secular Enlightenment and natural-rights traditions did. When Blight labels his subject the ‘prophet of freedom’, he means it in a biblical sense. Douglass turned to Holy Scripture and the Hebrew prophets to understand the meaning of African-Americans’ exile and suffering, the abolitionist crusade that culminated in the bloody carnage of civil war, the raising of black regiments to crush a rebellion, and the pursuit of renewal and cleansing in the reconstructed nation. The apocalyptic and millennialist tenor of his speeches gave Douglass his power as a latter-day prophet whose duty was to goad the public conscience while holding out the promise of a new Jerusalem.

Although these ideas influenced Douglass right up until his death in 1895, the prophetic themes had less straightforward purchase following the collapse of the rebel Confederacy in 1865. The mission of African-Americans was no longer the expunging of a calamitous sin through a single act of emancipation, but the creation of a racially equal society in the face of messy economic and cultural realities, political betrayal and the violence of lynch mobs. Unlike the radical abolitionist William Lloyd Garrison, who thought his job was done with the passage of the emancipatory Thirteenth Amendment, Douglass understood that a new chapter of his life was beginning. He would have to decide whether to remain the uncompromising outsider or, rather, to use the opportunities that his standing opened for him to serve in public office.

Had Abraham Lincoln survived to shape national reconstruction, he would have made ‘my friend Frederick Douglass’, as he called him, one of its agents. Of this we can be certain, for already in the summer of 1864 the president had sought his aid, asking him to take a lead in organising bands of black scouts to penetrate enemy lines, spread the word of emancipation and guide slaves to freedom. Exhilarated and daunted by the request, Douglass softened his previous view of Lincoln as a ‘heartless’ pragmatist. The challenge gave him a taste of what it would mean to engage in practical policymaking (though events made this particular liberation project redundant) and was a herald of what was to come: a postwar career as a Republican Party functionary, including service as marshal of the District of Columbia and US minister to Haiti. While discussing this, Blight takes his readers into new territory, exploring what he calls the ‘psychic dilemmas’ facing the ‘outsider-to-insider’ as he sought to influence policy from within the citadels of power.

Aware of Douglass’s shortcomings – he could be vain, occasionally arrogant and thin-skinned – and alert to his largely uncritical acceptance of such then-dominant ideas as self-reliance and the Native American ‘retreat’ from civilising modernity, Blight does not shy away from hard judgements. He exposes an inevitably more complex and flawed figure than the hero of the autobiographies. Yet by revealing the thorough humanity of one of the nation’s greatest voices for freedom, this rich portrait leaves Douglass with his greatness actually enhanced. Quite a feat.