Hume's Enlightenment Tract is the first full book-length study for forty years of David Hume's Enquiry concerning Human Understanding. The Enquiry has, contrary to its author's expressed wishes, long lived in the shadow of its predecessor, A Treatise of Human Nature. Stephen Buckle presents the Enquiry in a fresh light, and aims to raise it to its rightful position in Hume's work and in the history of philosophy. He argues that the Enquiry is not, as so often assumed, a mere collection of watered-down extracts from the earlier work. It is, rather, a coherent work with a unified argument; and, when this argument is grasped as a whole, the Enquiry shows itself to be the best introduction to the lineaments of its author's general philosophy. Buckle offers a careful guide through the argument and structure of the work. He shows how the central sections of the Enquiry offer a critique of the dogmatic empiricisms of the ancient world (Stoicism, Epicureanism, and Aristotelianism), and set in place an alternative conception of human powers based on the sceptical principles of habit and probability. These principles are then put to work, to rule out philosophy's metaphysical ambitions and their consequences: religious systems and their attendant conception of human beings as semi-divine rational animals. Hume's scepticism, experimentalism, and naturalism are thus shown to be different aspects of the one unified philosophy - a sceptical version of the Enlightenment vision.