The idea of religious liberty is sometimes thought to be necessary precisely because people will not agree on religious opinions. Yet the American tradition of religious freedom is grounded in the reality of both revealed religion and natural religion. While revealed religion, which is more contentious, is most often the subject of First Amendment cases, religious liberty need not presuppose that all religious knowledge is impossible. Instead, the Declaration of Independence famously affirms natural religion: that some things about God, human nature, and individual rights are knowable by reason. This chapter considers areas of natural religion, reason, and presuppositional thinking in order to show how knowledge is possible and how greater agreement can be achieved concerning religion.