The Principles of Moral and Christian Philosophy presents the first masterpiece of Scottish Common Sense philosophy. This two-volume treatise is important for its wide range of insights about the nature of the human mind, the foundations of morals, and the relationship between morality and religion. In order to understand the Enlightenment in Scotland, Turnbullβs work must be put next to that of Francis Hutcheson. In the first volume, The Principles of Moral Philosophy, Turnbull presents a detailed study of the faculties of the human mind and their interrelations. He contends that moral philosophy should be treated as one part, the highest part, of natural philosophy, and not as a field requiring its own distinctive methodology. Moral philosophers should rely on observation and experiment as their means of exploration into the workings of the human mind. In the second volume, Christian Philosophy, Turnbull presents arguments for the existence of God and for Godβs infinite perfection. The underlying notion here is Godβs moral government of the world, a government that is particularly at work in the allotment of recompense for our good and evil deeds. The Liberty Fund edition of The Principles of Moral and Christian Philosophy is the first modern edition of this work. George Turnbull (1698β1748) belongs to the founding figures in the Scottish Enlightenment. Finding their native Calvinism repressive, they sought a rational religion closely associated with their new science of human nature, supportive of tolerance, and compatible with classical ideals. Alexander Broadie is Professor of Logic and Rhetoric at the University of Glasgow. Knud Haakonssen is Professor of Intellectual History at the University of Sussex, England.