King undertook the final stage of his formal education at Boston University, to which he had won a fellowship on the basis of his performance at Crozer. At BU King refined his conception of God, incorporating tenets of personalism, a theological doctrine that stressed the personal nature of God and one's relationship to God, as well as the sanctity of human personality as a reflection of God's image. King's later rhetoric often incorporated these ideas. Although some critics have argued that King's doctoral thesis, entitled A Comparison of the Concepts of God in the Theology of Paul Tillich and Henry Nelson Weiman, contained plagiarized passages, King successfully received his PhD in 1955.
One of the most important developments in King's life in Boston occurred outside the classroom. In 1951 he met Coretta Scott, his future wife, a fellow Southerner who was studying voice at the New England Conservatory of Music. Initially Coretta had hesitations about being involved with a minister, but King was forthright in his courtship; indeed, on their first date he told her she had all the qualities he sought in a wife. They were married on 18 June 1953 by Martin Luther King, Sr., on the lawn of Coretta's family home in Marion, Alabama.
When King finished his coursework at BU, he took a post as the minister of Dexter Avenue Baptist Church in Montgomery, Alabama. It was an established church of well-educated middle-class blacks with a history of civil rights protest activity. At first King had mixed feelings about the position and considered work elsewhere, possibly at a place in which he could teach as well as preach. His salary was the highest black ministerial salary in town, however, and Montgomery, as the old capital of the Confederacy and thus a bastion of racism, probably seemed a suitable testing ground for a practitioner of a social gospel. At the end of 1955 Coretta gave birth to a baby girl, Yolanda Denise, whose arrival may have contributed to the couple's decision to stay.