That question is not as straightforward as you might think. Garry Wills' Head and Heart: American Christianities (Penguin Press, 2007) reviews these two different approaches and uses them to structure his history of Christianity in America. It is an effective format that helps the reader follow developments, in contrast to most histories of religion in America which are often overloaded with doctrinal and denominational details that have little interest for most contemporary readers.
The Head. In the section titled "Enlightenment Religion," Wills discusses how Unitarians, Quakers, and Deists emerged in the wake of the Great Awakening of 1740s. Not everyone liked what the Great Awakening stirred up: "Once men recoiled from emotional excess, they looked more carefully at how reason could be used to guide religion into more acceptable paths." Those paths included questioning the orthodox formulation of the Trinity (hence Unitarians) as well as other tenets of orthodox Calvinism (a turn to Arminian free will doctrines). Quakers rejected orthodox practice and doctrine in favor of simple benevolence and the inner light of the Spirit (what Mormons would call personal revelation). Deism was popular among the elites of the Revolutionary era, including Washington, Franklin, Jefferson, and most famously Tom Paine. Wills concludes:
It is one of this book's theses that Enlightened religion was a blessing to this country — that it was a necessary corrective to the pre-Enlightenment religion that hanged Mary Dyer, condemned Anne Hutchinson, and banished Roger Williams.
More on that in-need-of-correction pre-Enlightenment religion below.
The Heart. In the wake of the Revolution, established denominations like the Episcoplians and Congregationalists lost ground to newer, more enterprising groups like the Methodists and Baptists. The section titles in one of the chapters tell the story: Methodists, do-it-yourself religion, escaping doctrine. The Disciples of Christ, the denomination from which Sidney Rigdon and the hundred or so early Kirtland converts came, was firmly in this camp. As religion rolled into the 20th century, the trend away from doctrine became even more pronounced: nondenominational preachers like Dwight Moody and eventually Billy Graham sought nondenominational Christian converts, who increasingly attend nondenominational megachurches preaching do-it-yourself theology like dispensationalism, the health and wealth gospel, and Second Coming dramatics like The Late Great Planet Earth (published in 1970, it has sold over 28 million copies). The focus on conversion (of the heart) started with rural Second Great Awakening revivals and continues with present-day Christian festivals in arenas and stadiums.
So is Mormonism a religion of the heart or of the head?
Two Other Candidates. But wait, we have more options. First, before the two religious awakenings gave us our present denominational constellations, the Puritans of 17th-century New England were quite happily practicing their all-encompassing approach to Christianity. This is the "pre-Enlightenment religion" that Wills referred to in the above quotation. The term is meant to be descriptive, not pejorative. It refers to the era when learning and education were seen to be fully harmonious with Christianity: before secular learning and secular culture emerged during the Enlightenment, before scholarship subjecting the Bible to critical study had been published, and well before the theory of evolution and modern cosmology provided plausible naturalistic explanations of the cosmos, life, and humans.
There is a positive angle to how the Puritans did religion: The Puritans weren't Sunday-only Christians; they took their religion seriously. For them, religion, government, and community were all reflections of a unified Christian commonwealth, one which stressed duties more than rights, perhaps, but certainly had a strong sense of identity and mission. I tend to think Mormonism creatively adopts some features of the 17th-century paradigm, such as avoiding engagement with higher criticism of the Bible, generally discounting evolution, and at times practicing a form of mild theocracy. And don't forget Emerson's description of Mormonism as an "afterclap of Puritanism."
A second alternative to head or heart is political religion as it has emerged in the recent past. Religious involvement in cultural and legal fights over school prayer, abortion, and gay marriage are obvious signs of this political turn. Moral Majority, Christian Coalition, and the Religious Right familiar terms reflecting the politicization of religion in our generation. Mormonism has not been immune to this development. The ERA fight, Prop 22, Prop 8, and even the Proclamation on the Family highlight the extent to which politics and political issues now define Mormonism.
So, is Mormonism a religion of the heart, of the head, of pre-Enlightenment unity, or of modern political religion? ["All of the above" is not an allowable answer!]
Originally posted with comments at Times and Seasons.