An anti-skeptical transcendental argument can be loosely defined as an argument that purports to show that some experience or knowledge of an external world is a necessary condition of our possession of some knowledge, concept, or cognitive ability that we know we have. In this dissertation I examine transcendental arguments by focusing on one such argument given by Immanuel Kant in his Critique of Pure Reason, along with some attempts to interpret that argument by contemporary commentators. ;I proceed by dividing (...) anti-skeptical transcendental arguments into three types: epistemological, verificationist, and psychological. I examine arguments of the first two types and show why they cannot succeed against the skeptic. I then argue that Kant's Refutation of Idealism is of a different type: it is psychological in that it concerns the necessary conditions of our forming beliefs of certain kinds. Many contemporary Kant scholars have claimed that his anti-skeptical strategy relies on phenomenalism or verificationism; I argue, however, that Kant in the Refutation employs a clever and hitherto unappreciated strategy which involves an empiricist principle concerning the origin of simple ideas, and which does not require either phenomenalism or verificationism. I conclude with an analysis and assessment of Kant's argument. (shrink)