The above passage comes from a pamphlet written by David Hume to secure a readership for his largely unappreciated Treatise of Human Nature. Though not successful in this regard, the Abstract remains a valuable guide to Hume's Treatise, for it offers his own assessment of the significance of that work. Here, at least, Hume is unequivocal in describing his philosophy as “very sceptical.” But even if Hume describes his philosophy in this way, and even if, at the time, his philosophy was almost universally taken in this light, it remains unclear, first, what this scepticism amounts to and, second, how this scepticism is related to other aspects of his philosophical program. The goal of this essay is to answer both of these questions. I begin by giving a broad sketch of the role of scepticism in Hume's philosophy and then, in succeeding sections, offer a detailed analysis of the central sceptical arguments.