First, the founders did believe that religious people made good citizens because they knew how to sacrifice their own interests for something greater, namely their god. But the founders did not believe that religion, or particularly Christianity, was the only source of virtue. Metaxas is wrong when he says that “virtue and morality divorced from religion was unthinkable” to the founders (p.60). Most of the founders, including John Witherspoon, the evangelical Presbyterian clergyman who was the only minister who signed the Declaration of Independence, believed that virtue could stem from the conscience or the “moral sense.” Granted, many of them–whether Christian, Deist, or something in-between–believed that the conscience or moral sense was instilled in human beings by God, but they did not believe that a religious experience, the practice of a a specific faith, or the imbibing of particular religious doctrines was necessary to live a virtuous life.Three thoughts from me:
On p.66. Metaxas states that the “religion” that the founders thought was inseparable to a virtuous republic was not the religion of the “clockmaker God of Deist imagination,” but the religion of the Bible. (He quotes the Massachusetts statesman Daniel Webster on the importance of the Bible in creating citizens). Metaxas implies that “Deism” was not a religion that the founders thought could contribute to a virtuous republic because it did not adhere to the teachings of the Bible. But while Deists did not believe that the Bible was inspired, they did believe that the ethical teachings of the Bible could serve as a guide–one of several–to a virtuous life. In other words, Deism was certainly one of the so-called “religious” beliefs that the founders believed could contribute to the greater good of the republic.
1. Yes it's true that America's Founders thought that non-religious people could live the life of virtue necessary to sustain a republic, but thought such people tended to be rare; thus a "religious" citizenry would be preferred to a non-religious one.
2. Yes it's true that when America's Founders invoked "religion" necessary to sustain republics, they didn't necessarily mean "Christianity" of any kind (orthodox, unorthodox, deistic). Rather they believed a generally deistic or theistic minimum of the existence of a divine Providence and future state of rewards and punishments necessary. Hence the generic monotheism of America' Declaration of Independence.
Such could be found in Judaism, Islam, the various sects of "Christianity" (orthodox or not), pagan religions like Hinduism and Greco-Romanism and even non-Christian cold Deism (an absentee landlord God could, theoretically, so perfectly and tightly wind up His natural law clock, embedded in the release of which would reward virtue and punish vice both in this world and beyond).
3. Even though virtually all religions, Christian and non, were "valid" in this sense, Christianity still had the comparative advantage of containing Jesus' explicit moral teachings which were like shortcuts ordinary people who didn't have as George Washington put it, "the influence of refined education on minds of peculiar structure," to a perfected morality, the only thing about "religion" which civil republics were to be concerned. (Post John Locke government would no longer be in the business of "soulcraft," or caring about which religions could save men's souls.)