According to Oxford University Press's "World Christian Encyclopedia," 84% of the world's population belongs to some form of organized religion. That equals 5.7 billion people who belong to about 10,000 distinct religions, each of which may be further subdivided and classified. Christians, for example, may be apportioned among over 33,000 different denominations. Among the many binomial designations granted our species (Homo sapiens, Homo ludens, Homo economicus), a strong case could be made for Homo religiosus. And Americans are among the most religious members of the species. A 2007 Pew Forum survey of over 35,000 Americans...