Think of them as the three laws of spiritual physics when it comes to the demographics of faith. The bottom line is that religious groups thrive when:
* Believers have children.
* Believers pass their faith on to their children, the children retain that faith and some of these children even embrace vocations as clergy or workers with the faith.
* Believers reach out to others and spread the faith in service and evangelism.
As we like to say here at GetReligion: Demographics is destiny, and so is doctrine.
You could certainly see these factors at play in the recent "Global Catholicism: Trends & Forecasts"(.pdf copy here) conducted by the Center for Applied Research in the Apostolate at Georgetown University.
The bottom line: Catholicism is on ice in Europe and on fire in Africa and Asia. You can read some of the details in my "On Religion" column this week, but here's the bottom line: It's hard for a faith to survive, let alone thrive, when it isn't producing children, clergy and new believers. Heed these thoughts from CARA's Mark Gray: