Contrary to Mandeville's praise of private vice, Franklin “grew convinc’d” that certain virtues were necessary “in Dealings between Man and Man.” Hence Franklin, at the same time he began his own project for private virtue, simultaneously posited there was a public “Doctrine to be Preached.” While Franklin's list of virtues is in part a description of his own personal faults, he did not expect the average reader to acquire self-knowledge. He had, as scholars have suggested, a more political motive in mind—constructing a list of virtues founded in natural law to advance a new republican society. The one who could discover a method for a lasting virtuous reform, Franklin wrote Whitefield, would “deserve more, ten thousand times, than the inventor of the longitude.”

The great problem with constructing an art of virtue is the variety of human incentives, and their lack of direction. The naturally courageous man who desires recognition may become either a soldier or a butcher. A Christian's pride, when thwarted, may reemerge in injurious gossip. The political art requires that by skillful management these passions be turned to public advantage. In consideration of “the Strict Rules of Justice and Equity,” Franklin writes as early as 1723 that there are two sources of authority, the “Light of Nature and Laws of Justice.” “The end of Humane Law,” he adds, “is to fix the boundaries within which Men ought to keep themselves.” In his opposition to religious orthodoxy in the 1735 Hemphill affair, Franklin appealed to the “Laws of our Nature,” which could be accessed by human intelligence to formulate the “great Laws of Morality and Virtue.” While the moral laws were founded on the conclusions of reason, Franklin frequently appealed to an infinite God as the revelatory source of authority for these laws.

Yet, as Franklin wrote to Kames, there must also be a teaching for those who “cannot have Faith in Christ; and many have it in so weak a Degree, that it does not produce the Effect.” It is not enough that one who would be virtuous be convinced by arguments of virtue's advantages and then resolve to be virtuous.