Novelist Charles Johnson is best known as the only African American since Ralph Ellison to win the National Book Award. Thirty-eight years after the publication of Ellison's Invisible Man in 1952, Johnson's Middle Passage (1990) earned its author high praise from critics considering him an heir to Melville, Conrad and Swift as well as to Wright and Cleaver.

The civil rights activist Dr Martin Luther King Jr is the focus of Dreamer, Johnson's new novel, which is published next week in the UK. Set in Chicago during the last two years of King's life, Dreamer is a fictional account of King's encounter with his almost identical “double,” Chaym Smith.

Johnson's preparation for the novel was intense: he spent two years after Middle Passage researching King's sermons and collected papers and he studied documentary footage of the civil rights movement in Chicago from 1966 through to King's assassination on April 4, 1968. “I needed to understand this man better, I felt, than I did,” said Johnson in a recent interview, “so I read every scrap he managed to write from childhood forward.”

He emphasises that it is not just about King “. … it's also about doubles and the people who made possible the civil rights movement—black people prior to 1970 and going back to the period of reconstruction.” But Johnson has not ignored Yeats's admonition, “In dreams begin responsibility.” “I felt my primary responsibility,” Johnson explains, “was to deliver, particularly for those born after 1970, a portrait of this man that was not the airbrushed, canonised figure that we have come to celebrate every January 15.”

Particularly distressing to Johnson are the ways King's philosophy has been distorted. “After King's death, many people in America moved farther and farther away from his dream.” In Washington state, (where Johnson holds the Pollock chair in creative writing at the University of Washington) “we have a pro-gun group quoting King, who they say would see possession of firearms as a civil right. On the other end of the continuum we have Louis Farrakhan, who also feels free to quote King. My question is: what did this man actually say about various issues? A lot of that has been lost, as well as the scars and bruises of this remarkable man, who I think is one of the most important moral philosophers of the 20th century. I wanted to put those pores and scars and that sweat back on his brow, particularly during the last two, very difficult years of his life.”

Johnson finds it “compelling and interesting how little people across America knew this man. People know him as a civil rights leader, but they don't know him as a moral philosopher, as a man of the spirit.”

Apart from Johnson's mission to remind the world of King and his legacy, there was another factor which prompted the theme of the novel. “We began to hear in the 1980s and early '90s the tragic statistics about the situation of young black men in America,” he says, noting that in California, one in three black men between 16 and 34 are “controlled by the criminal justice system.” As the father of a son who was “in that critical age group” in '80s, Johnson began wondering, “Didn't King address these matters?”

King, he concluded, is more relevant than ever. “He said we have to fight on two fronts. One is the external battle against discrimination, injustice and segregation. The other is internal, it's looking inward, in terms of a constant, life-long effort for self-improvement and personal evolution, growth towards particular spiritual ideals. For King, you could not have success with one without having success with both.”

Johnson considers himself a philosophical novelist rather than a writer of historical fiction. Asked if the relation between the metaphysical aspects of Dreamer and its specific political milieu had been a balancing act, he answers: “King is a philosopher, so he gives me access to a broad canvas, to important moral and ontological ideas that relate to politics. I think that it's all one whole. It is a balancing act, but politics is very much a part of our lives, and I find the political realm interesting when we respond to its complexity.”

Johnson finds several of King's tenets “philosophically interesting.” Firstly, “the idea that non-violence is not just a strategy on civil rights demonstrations, but intended originally to be a way of life. Secondly, why he spoke so often of agape, or unconditional love, and why that was so important in terms of mediating racial situations in America and preventing black-white conflicts from becoming a power struggle. Thirdly, his belief, right down to the very end of his life, in integration. The way he articulates that at times demonstrates how our lives, our language, the clothes we wear, the furniture of our world are already inherently integrated.”

But American racial politics of the 1960s were, of course, bitterly defined by bifurcations. “The civil rights movement ultimately,” argues Johnson, “is about self and other. It's about black selves and white others, white selves and black others, and how we construct our identity.” So it's no surprise that fictional doubles recur in Johnson's work. “Doubles occur a lot, because the twin is our mirror, because our identity is social, it's based on a ‘we’ relationship, so the other person understands something about me I can't.”

The novel's conclusion alludes to Andrew Young's accusation that when King was shot, Jesse Jackson covered his palms with blood and then appeared bloodstained before the press. “I was haunted by the feeling,” says the young narrator Matthew Bishop, “that this act of theatre and falsity, this photo-op, would define the spirit of black struggle for decades after the minister's demise.” Asked whether this fear has been realised, Johnson looks to his exemplar: “I don't think in 30 years we've had a leader like Dr. Martin Luther King, who was a leader for all Americans, black and white. His last campaign was for poor Americans, blacks, Appalachians, Hispanics, Native Americans, everybody. I don't think we've had a leader who's spoken that way across racial divides, who has spoken so eloquently about the beloved community. I think that he was very special and that we've felt his absence as a kind of ache for 30 years now.”