Representationalism (also known as Representative Realism or Indirect Realism or Epistemological Dualism or the Representative Theory of Perception) is the philosophical position that the world we see in conscious experience is not the real world itself, but merely a miniature virtual-reality replica of that world in an internal representation. Thus, we know only our ideas or interpretations of objects in the world, because a barrier (or veil of perception) between the mind and the existing world prevents first-hand knowledge of anything beyond it.

Unlike Idealism, Representationalism holds that our ideas come from sense data (or images) of a real, material, external world (Realism), but that the immediate (direct) object of perception is only sense data that represents the external object. It approaches perception from a similiar point of view to Phenomenalism. It also entails a type of Dualism, such as that of Descartes.

Representationalists argue their case from the "epistemological fact" that it is impossible to have experience beyond the sensory surface, from the fact that dreams, hallucinations and visual illusions clearly indicate that the world of experience is not the same thing as the world itself, and from the evidence of phenomenal perspective (the curvature of perceived space, such as the apparent convergence of parallel road-sides, for example) which, they argue, is clearly not a property of the world itself, only of our perceptual representation of it.

Aristotle, in his work "On the Soul", was the first to describe how the eye must be affected by changes in an intervening medium rather than by objects themselves, and he reasons that, in order to avoid an infinite regress, the senses themselves must be self-aware.

The 17th Century philosopher John Locke was the most prominent advocate of this theory. He asserted that there are primary qualities which are "explanatorily basic" in that they can be referred to as the explanation for other qualities or phenomena without requiring explanation themselves (similar to the concept of Foundationalism), and that these qualities are distinct in that our sensory experience of them resembles them in reality. Secondary qualities (including colour, smell and taste) are those which one's experience does not directly resemble.

• Skeptics object that, since we only have knowledge of the representations of our perceptions, how is it possible to know for sure that they resemble in any significant way the objects to which they are supposed to correspond?
• If perception involves "pictures in your head", then who is it that is viewing those pictures (a homunculus?), and would it not result in an infinite regress of observers within observers?
• How can this theory be consistent with neurophysiology which presents the brain as an assembly of billions of discrete quasi-independent local processors interconnected in a massively parallel network?
• Even if there is a spatial representation in the brain, why (and how) should it be conscious of itself?