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Representative Theory of Perception, also known as Indirect realism, epistemological dualism, and The veil of perception, is a philosophical concept. It states that we do not (and can not) perceive the external world directly; instead we know only our ideas or interpretations of objects in the world. Thus, a barrier or a veil of perception prevents first-hand knowledge of anything beyond it. The "veil" exists between the mind and the existing world.

The debate then occurs about where our ideas come from, and what this place is like. An indirect realist believes our ideas come from sense data of a real, material, external world (unlike idealists). The doctrine states that in any act of perception, the immediate (direct) object of perception is only a sense-datum that represents an external object.

Aristotle was the first to provide an in-depth description of Indirect realism. In "On the Soul" he describes how the eye must be affected by changes in an intervening medium rather than by objects themselves. He then speculates on how these sense impressions can form our experience of seeing and reasons that an endless regress would occur unless the sense itself were self aware. He concludes by proposing that the mind is the things it thinks. He calls the images in the mind "ideas".

The way that indirect realism involves intermediate stages between objects and perceptions immediately raises a question: How well do sense-data represent external objects, properties, and events? Indirect realism creates deep epistemological problems, such as solipsism and the problem of the external world. Nonetheless, Indirect realism has been popular in the history of philosophy and has been developed by many philosophers including Bertrand Russell, Spinoza, René Descartes, and John Locke.[1] Representationalism is one of the key assumptions of cognitivism in psychology.

Potential results of representative realism


A problem with representationalism is that if simple data flow and information processing is assumed then something in the brain, described as a homunculus, must be viewing the perception. This suggests that some physical effect or phenomenon other than simple data flow and information processing might be involved in perception. This was not an issue for the rationalist philosophers such as Descartes, since Cartesian dualism held that there is a supernatural "homunculus" in the form of the soul. For those who doubt dualism, explaining precisely what it is that sees the representation is problematic. But if the transfer of information into a "mind" is thought to be the only explanation of how we indeed see, then it falls foul of the homunculus fallacy which would suggest that either representationalism is an incomplete or invalid description of perception or some supernatural intervention or non-materialist, physicalist explanation is needed. Aristotle realised this and simply proposed that ideas themselves (representations) must be aware - in other words that there is no further transfer of sense impressions beyond ideas.



A further difficulty is that, since we only have knowledge of the representations of our perceptions, how is it possible to show that they resemble in any significant way the objects to which they are supposed to correspond? Any creature with a representation in its brain would need to interact with the objects that are represented to identify them with the representation. According to this theory, the external world is only to be inferred, the person needing to learn about the relations between their electrochemical perceptions and the world.


A difficulty arises when attempting to explain reference using representationalism. If I say "I see the Eiffel Tower" at a time when I am indeed looking at the Eiffel Tower, to what does the term "Eiffel Tower" refer? One might wish to say it refers to the Eiffel Tower, but since in the representational account we do not really see the tower, presumably the reference is to our sense experience. But this would mean that when I refer to the Eiffel Tower, I am referring to my sense experience, and when you refer to the Tower, you are referring to your sense experience. Therefore when we each refer to the Eiffel Tower, we are not referring to the same thing — an apparent absurdity. The problem is similar to each of us seeing a picture of the Eiffel Tower on our own television, where we should be aware that our televisions might be different.

Bertrand Russell

Representative realism does, unlike naïve realism, take into account sense data (the way in which the object is interpreted, not simply the objective, mathematical object) - this induces the veil of perception wherein we are unsure the table we look at exists due to there being no direct objective proof of existence. In other words, the table I'm looking at appears to have a particular shape to me, due to my angle of vision, and to have a particular colour due to the way in which the light bounces off it relative to my position, and that appearance differs from the appearance of the table as seen by the person next to me. Each of us sees not the actual table, but an appearance of it which merely represents an actual table out there.

The representative theory of perception states that we do not perceive the external world directly; instead we perceive our personal interpretation of an object by way of sense data. A naïve realist assumes she sees the dog upon perceiving a dog, whereas a representative realist assumes she sees a sensory representation of the dog upon perceiving a dog.

The external world is real and continues to exist unobserved. But we are only aware of it indirectly. Our perception of the external world is mediated by way of sense data such as photons and sound waves. We perceive a representation of reality (not the reality itself); this has been given many names: ideas, sense data, percept or appearance.

Thus representative realism is the idea that our perceptions are directly caused by the intrinsic qualities of objects, and based on these perceptions we can infer things about these objects.

John Locke

The 17th century philosopher John Locke most prominently advocated this theory. The term they used was not "sense-datum" but "idea." "Idea" as used in the theory of perception is a technical term, meaning roughly the same thing as sense-datum, and this article does not discuss any differences in meaning that the two terms might have.

John Locke thought objects had two classes of qualities:

  • Primary qualities are qualities which are 'explanatorily basic' - which is to say, they can be referred to as the explanation for other qualities or phenomena without requiring explanation themselves - and they are distinct in that our sensory experience of them resembles them in reality. (For example, one perceives an object as spherical precisely because of the way the atoms of the sphere are arranged.) Primary qualities cannot be removed by either thought or physical action, and include mass, movement, and, controversially, solidity (although later proponents of the distinction between primary and secondary qualities usually discount solidity).
  • Secondary qualities are qualities which one's experience does not directly resemble; for example, when one sees an object as red, the sensation of seeing redness is not produced by some quality of redness in the object, but by the arrangement of atoms on the surface of the object which reflects and absorbs light in a particular way. Secondary qualities include colour, smell, and taste.


In contemporary philosophy, epistemological dualism has come under sustained attack by philosophers like Wittgenstein (the "private language" problem) and Wilfrid Sellars in his seminal essay "Empiricism and the Philosophy of Mind." Indirect realism is argued to be problematical because of Ryle's regress and the apparent need for a homunculus. These problems have led some philosophers to abandon realism and suggest the existence of dualism and others to propose, or suggest through emergentism, that some form of new physics is operating in the brain such as quantum mind, space-time theories of consciousness etc.

Scientific Consensus for Representative Realism?

The debate for and against representative realism has likely been raging for as long as there have been philosophers. How has the amount of consensus amongst experts for one side or the other changed over history? Could a revolution be taking place and one side significantly breaking out in the lead amongst experts during the last few decades?

There is a tool being developed at with the goal of rigorously measuring scientific consensus going forward. There is a new topic getting started on theories of consciousness. All experts and non experts are invited to quantitatively communicate to everyone what they currently think on this issue. The more people that get involved, the more comprehensive the survey data will be.

Out of the gate the scientific consensus is clearly in the Consciousness is representational and real camp with such distinguished supporters as Steven Lehar, John Smythies and a growing number of others. But perhaps this early lead is just because supporters of some other more well accepted theory of consciousness haven't yet started supporting their ideas here?

There is obviously always the possibility that demonstrable scientific results are about to be achieved that will convert everyone to the 'true' camp. Surely such, the scientific discovery of what the mind truly is, would be amongst the greatest scientific achievements of all time. Or maybe the camps that claim we will never know are the ones that are right?

External sources

See also

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