Abstract: This paper argues that in attempting to protect the religious life from the sullying influence of worldly affairs, Roger Williams participated, albeit unintentionally, in creating the economic conditions that led to the birth of American capitalism. Although Williams argued for a separation of church and state, he did so not in the interest of defending economic liberty, but instead to preserve the sanctity of the church against the frequent immorality that seemed to him required in worldly governance. Questions of pricing and wages, lending and interest—issues that would until Williams’s intervention have been handled by the church in terms of Aquinas’ just price theory—fell outside of the church’s purview according to the new model described by Williams. The result was the creation of an “amoral” public space where the effective separation between spiritual and material concerns led to a kind of free-by-default economic marketplace. This paper traces the development and inadvertent consequences of this essentially theological idea as it took shape in the colonial era.