The Enlightenment saw the emergence of the “philosophes” in Europe—intellectuals who were unafraid to publicly challenge … well, just about everything. But Britain’s American colonies weren’t without their own philosophers. The most famous was certainly Benjamin Franklin, the grandson of an indentured servant and the son of a candlemaker. Unlike many of Europe’s thinkers, however, Franklin preached a philosophy of practicality. Brought up without much formal schooling, Franklin mastered the printing trade while working as a teenager in his older brother’s print shop, where the young man also had access to the latest intellectual developments of the Western world. Teenaged Franklin would read articles from Europe’s premier journals over and over, delighting not just in new knowledge but also in the writing itself and often “wish[ing] if possible to imitate it.” At 17, Franklin found print work in Philadelphia, then in London. But at 20, he was back in Philadelphia, …