“What would it mean for Christians to rediscover their faith not as a problematic system of beliefs but as a just and generous way of life, rooted in contemplation and expressed in compassion?” McLaren asks in “The Great Spiritual Migration.” “Could Christians migrate from defining their faith as a system of beliefs to expressing it as a loving way of life?”

That would be a migration away from religious bureaucracy and back to the moral vision of the founder, and it would be an enormous challenge. But religion can and does migrate.

“Because I grew up in a very conservative Christian context, we were always warned about changing the essential message,” McLaren told me. “But at the same time, we often missed how much actually had changed over time.” Christianity at times approved of burning witches and massacring heretics; thank goodness it has evolved!