Soon after the death of his child Francis, Benjamin Franklin was moved to set down his religious beliefs in an address he gave to a group of philosophically inclined friends known as "the Junto." Though he committed these ideas to paper more than 60 years before his death, they would serve as the basis for his understanding of the divine to the end of his life. In this description of Franklin's beliefs from Walter Isaacson's new book, "Benjamin Franklin: An American Life," we can see the seeds of skepticism, attachment to virtue and above all tolerance that would be Franklin's legacy to the nation.

In London [in 1725], Franklin had written his ill-conceived "Dissertation on Liberty and Necessity," which attacked the idea of free will and much of Calvinist theology, and then he had repudiated the pamphlet as an embarrassing "erratum." That left him in a religious quandary. He no longer believed in the received dogmas of his Puritan upbringing, which taught that man could achieve salvation only through God's grace rather than through good works. But he was uncomfortable embracing a simple and unenhanced version of deism, the Enlightenment-era creed that reason and the study of nature (instead of divine revelation) tell us all we can know about our Creator. The deists he knew, including his younger self, had turned out to be squirrelly in their morals.

On his return to Philadelphia, Franklin showed little interest in organized religion and even less in attending Sunday services. Still, he continued to hold some basic religious beliefs, among them "the existence of the Deity" and that "the most acceptable service of God was doing good to man." He was tolerant of all sects, particularly those that worked to make the world a better place, and he made sure "to avoid all discourse that might tend to lessen the good opinion another might have of his own religion." Because he believed that churches were useful to the community, he paid his annual subscription to support the town's Presbyterian minister, the Rev. Jedediah Andrews.

One day, Andrews prevailed on him to sample his Sunday sermons, which Franklin did for five weeks. Unfortunately, he found them "uninteresting and unedifying since not a single moral principle was inculcated or enforced, their aim seeming to be rather to make us good Presbyterians than good citizens." On his final visit, the reading from the Scripture (Phillipians 4:8) related to virtue. It was a topic dear to Franklin's heart, and he hoped that Andrews would expound on the concept in his sermon. Instead, the minister focused only on dogma and doctrine, without offering any practical thoughts about virtue. Franklin was "disgusted," and he reverted to spending his Sundays reading and writing on his own.

Franklin began to clarify his religious beliefs through a series of essays and letters. In them, he adopted a creed that would last the rest of his life: a virtuous, morally fortified, and pragmatic version of deism. Unlike most pure deists, he concluded that it was useful (and thus probably correct) to believe that a faith in God should inform our daily actions; but like other deists, his faith was devoid of sectarian dogma, burning spirituality, deep soul-searching, or a personal relationship to Christ.

The first of these religious essays was a paper "for my own private use," written in November 1728, entitled "Articles of Belief and Acts of Religion." Unlike his London dissertation, which was clogged with convoluted imitations of analytic philosophy, it was elegant and sparse. He began with a simple affirmation: "I believe there is one Supreme most perfect being."

It was an important statement, because some mushier deists shied even from going that far. As Diderot once quipped, a deist is someone who has not lived long enough to become an atheist. Franklin lived very long, and despite the suspicions of John Adams and others that he was closet atheist, he repeatedly and indeed increasingly asserted his belief in a supreme God.

In the deist tradition, Franklin's Supreme Being was somewhat distant and uninvolved in our daily travails. "I imagine it great vanity in me to suppose that the Supremely Perfect does in the least regard such an inconsiderable nothing as a man," he wrote. He added his belief that this "Infinite Father" was far above wanting our praise or prayers.

There is in all humans, however, a desire and a deeply felt duty to worship a more intimate God, Franklin surmised. Therefore, he wrote, the Supreme Being causes there to be lesser and more personal gods for men to worship. Franklin thus has it both ways: combining the deist concept of god as a distant First Cause with the belief of other religions that worship a God who is directly involved in people's lives. The result is a Supreme Being that can be manifest in various ways, depending on the needs of difference worshipers.

Some commentators, most notably A. Owen Aldridge, read this literally as Franklin's embracing some sort of polytheism, with a bevy of lesser gods overseeing various realms and planets. Occasionally throughout his life, Franklin would refer to "the gods," but these later references are quite casual and colloquial, and Franklin seems to be speaking more figuratively than literally in his 1728 paper. As Kerry Walters writes in "Benjamin Franklin and His Gods," "It is an error to presume the point to a literal polytheism. Such a conclusion is as philosophically bizarre as it is textually unwarranted." (Given the difficulties Franklin sometimes seems to have believing in one God, it seems unlikely he could find himself believing in many.)