Evangelicalism is hard to define. Is it a movement? An institution? Can it be described by a set of necessary beliefs? Historians are of many opinions; some even going so far as to deny that evangelical, as it is commonly used, is a valid term. Mark Noll of Notre Dame, in his The Rise of Evangelicalism, has some helpful thoughts:
“Evangelicalism” is too loose a designation ever to have produced a tidy historical record. To be sure, some thoroughly evangelical denominations possess well-organized and conveniently available archives. But many evangelicals have been active in mixed denominations where evangelical emphases exist alongside other convictions. Evangelicals have also established many stand-alone churches of the sort that are always difﬁcult to document. And still more evangelicals have devoted much of their energy to multidenominational voluntary societies. Difﬁculties in controlling the subject notwithstanding, it is still possible to present a coherent history of evangelicalism as deﬁned by genealogy and by principle.
By the same token, however, it is important to realize that the emphases of evangelicalism have shifted as they came to expression in different times and places. The late Canadian historian, George Rawlyk, who did so much to promote study of evangelical churches and movements in his native land, shrewdly observed on several occasions that evangelicalism has constituted a ﬂuid subject.
The four main principles identiﬁed by David Bebbington do not exist in the same proportions or exert the same effects in all times and places. Sometimes the experience of conversion takes precedence, at others the concentration on Scripture as ultimate religious authority and at still others the importance of missionary or social action. The evangelical traditions consistently maintain the major evangelical traits, but they have done so with a tremendously diverse array of emphases, relationships and special concerns.
Mark Noll, The Rise of Evangelicalism: The Age of Edwards, Whitefield and the Wesleys A History of Evangelicalism (Downers Grove, Illinois: InterVarsity, 2003), 20.