The discourse of America's founding generation, it is now widely recognized, was rich and variegated in its composition, drawing upon the commonwealth tradition, the English common law, Montesquieu, Locke, Scottish moral philosophy, and the classics. These sources yield significant clues as to how eighteenth-century Americans viewed religious liberty and church–state relations, subjects of the First Amendment to the Constitution. Supplementing the work of legal historians on the religious provisions of the early state constitutions, the study of political ideas suggests the parameters of the eighteenth-century debate over the effects which various types of religious belief and ecclesiastical establishment had upon manners and institutions. It also reveals the ideological underpinnings of the apparently inconsistent legal provisions for religion at the state level, and, far from settling the elusive question of ‘original intent’, highlights the nature of the divisions within the founding generation.