Pottenger says these three factors form an interlocking foundation of modern cultures:
1) The world should be understood through rational and empirical examination;
2) Individuals should develop personal ethics, as through conscience;
3) Society should not simply grant religious toleration to non-favored religions, but religious liberty to all.
In this book the third point is the one he works the most with. He is argues that liberal democracy must fight against its tendency to institutionalize the majority faith. It would be easy to elevate the faith of the majority, and only tolerate the other faiths. It is particularly tempting to enshrine the founding faith of a society as the permanent basis of its culture, no matter what changes later in the composition of the population or the culture of the world.
What liberal democracies must do, he argues, is establish religious liberty for all, not just religious toleration. This is an interesting idea, and certainly has many consequences for politics. He considers Christian Reconstructionism, old-time Mormonism, and Uzbekistan's embrace of Islamic nationalism as all bad moves away from religious liberty toward mere toleration.
I think Pottenger makes some important mistakes. In particular, he does not credit the difference between changing the culture by religiously converting individuals, and changing the state by religiously changing the laws. He is right in criticizing the Christian Reconstructionism of Rousas Rushdoony as trying to do the latter. He is wrong in treating garden-variety evangelicals, who do aim at individual conversion within a secular state, as doing the same thing as the Reconstructionists.
Nonetheless, I think Pottenger does a service to the religion and politics discourse by making a clear distinction between religious liberty and religious toleration.