Every other entry of this kind in the atlas can point to a document: a confession, a council, a papal constitution, a synodical decree. Evangelicalism has none, because it is a movement across churches rather than a church, with no synod that could adopt a confession and no membership that could be bound by one. The definition in general use was therefore supplied by a historian describing the movement from outside it.
David Bebbington, writing Evangelicalism in Modern Britain in 1989, identified four persistent marks: conversionism, the conviction that a life must be changed and that the change can be spoken of; biblicism, a particular regard for the Bible as the authority to which appeal is made; crucicentrism, a concentration of doctrine and devotion on the atoning death of Christ rather than on the incarnation or the church; and activism, the expectation that belief issues in preaching, mission and social effort. The four marks were taken up with unusual speed, by evangelical institutions and their critics alike, and they now function as the movement's working self-description, which is a curious fate for an outsider's analytic tool. Their value is that they identify something real. An evangelical Anglican, an evangelical Baptist and an evangelical Pentecostal disagree about baptism, bishops and the gifts of the Spirit while recognizing one another immediately by these four emphases, and the recognition is what makes the transdenominational institutions of the movement possible.