Abstract

The historically most central epistemological issue concerning perception, to which this article will be almost entirely devoted, is whether and how beliefs about physical objects and about the physical world generally can be justified or warranted on the basis of sensory or perceptual experience—where it is internalist justification, roughly having a reason to think that the belief in question is true, that is mainly in question (see the entry justification, epistemic: internalist vs. externalist conceptions of). This issue, commonly referred to as “the problem of the external world,” divides into two closely related sub-issues, which correspond to the first two main sections below. The first of these issues has to do with the nature of sensory experience and its relation to the physical world; it is typically (though as we shall see not altogether perspicuously) formulated as the question of what are the immediate objects of awareness in sensory experience or, in a variant but essentially equivalent terminology, of what is given in such experience. Perhaps the most historically standard, though not currently the most popular answer to this question has been that it is sense-data (private, non-physical entities that actually have the immediately experienced sensory qualities) that are the immediate objects of awareness or that are given. The second issue has to do with the way in which beliefs about the physical world are justified on the basis of such sensory experience. If it is concluded that physical objects are not themselves given, the two main answers to this question are representationalism or indirect realism (the view that the immediate objects of experience represent or depict physical objects in a way that allows one to infer justifiably from such experience to the existence of the corresponding “external” objects) and phenomenalism (the view..