Over here, Davey Henreckson has an intriguing synopsis of Grant Wacker’s Heaven Below, an examination of the growth of early Pentecostalism. I haven’t read Wacker’s book myself, but his argument (as per Henreckson), that Pentecostalism gained traction as a result of two emphases (pragmatism and primitivism) strikes me as accurate. By pragmatism, I assume Wacker is referring to the great adaptability and free experimentation with church form that characterizes so much of Pentecostalism. Rather than drawing on a set liturgy or church authorial structure, Pentecostal churches vary widely in their size, location and organization. By primitivism, Wacker means the sense that in the Pentecostal movement, we are returning to the original teaching of the apostles and the life of the Church in Acts (especially Acts 2). These two emphases, combined with the oft-noticed appeal of Pentecostalism’s focus on heavenly reward, gets at much of what the movement was about in the early 20th century. Of course, in the latter half of that century the movement spread and became more diffuse in its influences and emphases, but that is another book.