Arguments and closure

Suppose that you believe a claim because it is the conclusion of an argument that you are justified in believing is sound. Then I think you are justified in believing that claim. Or suppose that you believe a claim because it is the conclusion of an argument that you know is sound. Then I think you know that that claim is true. I do not think I am alone here. I think that philosophers often assume that they are justified in believing (or know) a claim simply because they believe that claim on the basis of an argument that they are justified in believing (or know) is sound. But this assumption is threatened by familiar objections to epistemic closure. The main goal of this paper is to defend the philosophical practice of both giving and also evaluating arguments that aim to justify (or render known) conclusions. It does so by arguing that this practice turns on a particular closure principle, and then defends that closure principle. This paper also shows how the conclusions it defends about the practice of giving arguments to justify (or render known) conclusions bear on a paradox about knowledge from Kripke, on contextualism, and on the paradox of the preface.