Secular Humanism in the United States

The groundwork for modern humanism was laid during the Enlightenment by those philosophers who sought to purge religion of most of its superstitious elements and replace them with a deistic or atheistic rationalism. Thomas Paine's Age of Reason (1794–1796), which argues for a religion based on a belief that the world was created by a rational God, was one of the most important such works in this period.

In the nineteenth century, two major influences were important. First, at an institutional level, the Unitarian Church came into existence and by century's end had developed a commitment to toleration and a disavowal of any type of creedalism. This development, combined with the Unitarians' progressive, liberal ideology, created a framework that would accept the kind of religious radicalism that humanists came to espouse in the early twentieth century. The fact that humanism came to be institutionalized in the Unitarian Church would be both fortunate and problematic.

One of the most significant intellectual transformations of the nineteenth century was the widespread acceptance of a developmental view of the past. This revolution in thought had a profound effect on modern religious history. Although many people found ways to reconcile biological evolution and traditional religion, naturalistic evolution gave ammunition to critics of Christianity who branded it as intellectually stagnant and naïve. More important, however, developmentalism also made it possible to see human history as in flux; indeed when applied to religious history, it had the effect of relativizing religion. Humanism drew on both aspects of evolutionary thinking.