A thorough, textured analysis of the sources and strategies of Martin Luther King's preaching and rhetoric. Lischer (Homiletics/Duke Univ. Divinity School) argues that focusing on King's thought as expressed in his ``derivative'' academic work scants the ``stunning creativity'' of his achievement in articulating the values and aspirations of the civil rights movement. Thus, in trying to locate King's true voice, Lischer relies on sources that he says many biographers overlook: audiotapes and unedited transcripts of King's sermons and speeches. He traces King's development as a ``preacher's kid,'' inheriting the Baptist Church's mixed heritage of resistance and faith in otherworldly relief. At Morehouse College, King found another influence in the intellectual idiom of the school's president Benjamin Mays; later, at Crozer Seminary and Boston University, he drew on broader religious traditions but never lost his grounding in the black community and church. Thrust into prominence at 26 as a Montgomery, Ala., church leader, King responded with his rich intellectual and spiritual resources; in one of several insightful critiques, Lischer shows how the preacher galvanized his audience by using repetition of the word ``tired'' to connect historical black grievances with contemporary humiliations. The author demonstrates how King drew on an enormous range of material--poems, gospel formulas, paragraphs from speeches of popular white preachers--and inserted them ``like numbers on a jukebox'' for maximum effect. Lischer also shows how King was able to speak authentically to blacks, yet also reach the larger society by linking social reform with the country's dominant Christianity. He concludes with analyses of King's choices of biblical preaching texts, his ``first draft'' style of preaching, and, fascinatingly, his powerful voice at mass organizing meetings. Lischer argues that King was able to frame a broadly based rationale for racial equality in a historical moment that has since passed. Worthy stuff, but more detail than most readers will want.