Now, the belief that these are the mainline denominations simply won't go away. Everyone keeps pretending that these are the folks that count. But the fact is: that's ancient history.

Back in 1972, a marvelous man named Dean Kelley -- he was an executive in the National Council of Churches -- wrote a book in which argued that something really remarkable is happening: the mainline denominations are shrinking. More remarkably, the conservative churches are growing. It isn't as though religion is going out of style; it's just that people are going to different churches.

He was pilloried for that book and its claims, but it was all true. And of course, these denominations have continued to lose members at an incredible rate, and they're tiny now compared to what they were, say, in 1960. Yet one keeps hearing about the "mainline" denominations and this "periphery" called evangelicalism. Well, the periphery is now the mainline, and the mainline is the sideline.

I also decided to write this book partly because of the misperception that this transformation began in the 1960s. The 1760s may be more accurate, and certainly the 1860s, but it didn't start in the 1960s. The 1960s is just when it began to be noticed.

What was really happening was this. As denominations got liberal, they started to shrink. Which means that the Methodists started to shrink much later than the Congregationalists, the Episcopalians, and the Presbyterians. But rapid population growth masked this decline for many, many decades. So at the end of every year, the Congregationalists and Episcopalians would look around and notice that they had more members than the year before. But through this whole period, their share of the market was declining. When you calculate that, you suddenly see a very different picture. These groups had been going downhill for a very long time.

What happened in the 1960s is that finally their declines became so extended, and so rapid, that for the first time there were fewer at the end of the year than at the start of the year. That's what prompted a book like Kelly's in the 1970s, because for ten years or more the old mainline had noticed that they were losing membership in an absolute and not just a proportional sense.

If the timeline for the decline is shifted, how does that affect our understanding of the reasons that brought about the decline in the first place?

Once you realize that the decline didn't start in the 1960s, you end up having to go back well into the 19th century in search of the reasons, and you find two. The first is modernist theology. The theology that prevailed in the mainline churches changed dramatically. If you take Paul Tillich's view of God, in which God is essentially something imaginary, then why do you bother to hold a church service in the first place? If there's nothing there to pray to, why do it? The liberal clergy lost their faith, but they continued to hold church.

The second factor was, when the clergy in the mainline denominations decided that they could no longer save souls -- because there were no souls to save -- they decided that they should save the world instead. They switched from religion to politics, and that was a politics of Left-wing radicalism.

It's fine, of course, to be a Left-wing radical. But it was far out of step with the people in the pews. The people in the pews still believed in God, and the people in the pews did not believe that they needed a socialist government next week. Consequently, they stopped sitting in those pews and started going to other pews.