The central problem in the epistemology of perception is that of explaining how perception could give us knowledge or justified belief about an external world, about things outside of ourselves. This problem has traditionally been viewed in terms of a skeptical argument that purports to show that such knowledge and justification are impossible. Skepticism about the external world highlights a number of epistemological difficulties regarding the nature and epistemic role of experience, and the question of how perception might bring us into contact with a mind-independent reality. The issues that arise are of central importance for understanding knowledge and justification more generally, even aside from their connection to skepticism.
Two main types of response to the skeptical argument have traditionally been given: a metaphysical response that focuses on the nature of the world, perceptual experience, and/or the relation between them, in an effort to show that perceptual knowledge is indeed possible; and a more directly epistemological response that focuses on principles specifying what is required for knowledge and/or justification, in an effort to show that skepticism misstates the requirements for knowledge.