According to common sense, perception, the exercise of the five senses, is the chief means by which we know about the world around us. For this reason, a basic understanding of the nature of perception is important to epistemology. A theory of perception should answer such questions as: What is it to perceive something?, What sorts of things does perception make us aware of?, and How does perception enable us to gain knowledge of the world around us? The reading selections in this chapter discuss four traditional philosophical positions, each of which addresses one or more of those questions:

1. Representationalism, also known as “indirect realism,” maintains that in perception, we are directly aware of certain internal, mental states or entities-referred to by various philosophers as “ideas” (Locke), “impressions” (Hume), “mental images,” or “sense data” (Russell)—and we are indirectly aware of external things (that is, our awareness of them depends on our awareness of the images). The mental images are usually said to be caused by external, physical objects/events and to “represent” the latter. Representationalists usually also say that we can have knowledge or justified beliefs about the external world by inferring facts about external objects from the character of the mental images. Usually, it is thought that the hypothesis of external objects (objects existing independent of the mind) having certain characteristics provides the best explanation for why we have the sort of sense data that we do. Representationalism, more than any other position, probably deserves to be called the traditional theory of perception among philosophers.