One of the foundation stones of a mere Christendom has to be a root and branch rejection of Darwinism. The reason for this is not hard to ascertain — Darwinism is one of the chief cornerstones of the secular state.
We are acquainted with the standard liberal metaphor of the Constitution as a “living document,” which means, when translated, that the Constitution never gets in the way of what they currently want to do. This makes sense if the universe actually is that way — if it is the kind of place where anything is capable of evolving into anything else. In a universe in which everything morphs, where everything is in flux, it only makes sense. But if a republic is a republic “after its kind,” then it can only be dishonestly morphed into something else by men who deny that. One of the cheapest and easiest ways of making a republic do the shape-shifting thing is by changing the kind of universe everybody thinks they are living in.
When our republic was founded, Darwin’s Origin was still well off in the future. After Darwin, aspirants to the throne of God were delighted to find out that the world was a just a giant vat of PlayDough, and that they could take gobs of it into their two hands whenever they wanted, and make whatever they wanted. Turns out one of the things they wanted was lots of power for the state, and no heaven above them. Just imagine it. Easy if you try.
In a Darwinian world, the reestablishment of any kind of Christendom would be a vain enterprise, because you couldn’t look away for ten minutes. This is why countries where the Christian faith is established have been able to become just as secular as countries without an establishment. Evolution knows how to work around things. Some turtles have to learn how to fly with the shell, and some don’t.
I have a younger brother who is the black sheep of our family — he was the one who became a scientist. He has a phrase I like, which is, “Intelligent Design: The Understatement of the Century.” But as grateful as I am for the work of the first wave creationists, and as happy as I am about how the ID folks are giving the academy fits, we will not ready for mere Christendom until evolution, in all its forms, is simply a laughingstock. Just as Jesus said that certain demons could not be driven out except by prayer and fasting, so certain intellectual errors cannot be gotten to except by means of the horse laugh.
This whole issue, incidentally, exposes the posturing of virtually all those who call themselves postmodernists. Modernism is thoroughly dependent on Darwin, and so it is not possible to be a real postmodernist without being a post-Darwinist. And if you are really a post-Darwinist, then that makes you a post-secularist, making you, in turn, a theocrat. Somehow this is a line of argument that eludes Brian McLaren.