Philosophy of perception

The philosophy of perception is concerned with the nature of perceptual experience and the status of perceptual data, in particular how they relate to beliefs about, or knowledge of, the world.[1] Any explicit account of perception requires a commitment to one of a variety of ontological or metaphysical views. Philosophers distinguish internalist accounts, which assume that perceptions of objects, and knowledge or beliefs about them, are aspects of an individual's mind, and externalist accounts, which state that they constitute real aspects of the world external to the individual.[1] The position of naïve realism—the 'everyday' impression of physical objects constituting what is perceived—is to some extent contradicted by the occurrence of perceptual illusions and hallucinations[2] and the relativity of perceptual experience[1] as well as certain insights in science.[3] Realist conceptions include phenomenalism and direct and indirect realism. Anti-realist conceptions include idealism and skepticism.[1]

Grey square optical illusion proof2
Do we see what is really there? The two areas of the image marked A and B, and the rectangle connecting them, are all of the same shade: our eyes automatically "correct" for the shadow of the cylinder.

Categories of perception

We may categorize perception as internal or external.

  • Internal perception (proprioception) tells us what is going on in our bodies; where our limbs are, whether we are sitting or standing, whether we are depressed, hungry, tired and so forth.
  • External or sensory perception (exteroception), tells us about the world outside our bodies. Using our senses of sight, hearing, touch, smell, and taste, we perceive colors, sounds, textures, etc. of the world at large. There is a growing body of knowledge of the mechanics of sensory processes in cognitive psychology.
  • Mixed internal and external perception (e.g., emotion and certain moods) tells us about what is going on in our bodies and about the perceived cause of our bodily perceptions.

The philosophy of perception is mainly concerned with exteroception.

Scientific accounts of perception

An object at some distance from an observer will reflect light in all directions, some of which will fall upon the corneae of the eyes, where it will be focussed upon each retina, forming an image. The disparity between the electrical output of these two slightly different images is resolved either at the level of the lateral geniculate nucleus or in a part of the visual cortex called 'V1'. The resolved data is further processed in the visual cortex where some areas have specialised functions, for instance area V5 is involved in the modelling of motion and V4 in adding colour. The resulting single image that subjects report as their experience is called a 'percept'. Studies involving rapidly changing scenes show the percept derives from numerous processes that involve time delays.[4] Recent fMRI studies [5] show that dreams, imaginings and perceptions of things such as faces are accompanied by activity in many of the same areas of brain as are involved with physical sight. Imagery that originates from the senses and internally generated imagery may have a shared ontology at higher levels of cortical processing.

Sound is analyzed in term of pressure waves sensed by the cochlea in the ear. Data from the eyes and ears is combined to form a 'bound' percept. The problem of how this is produced, known as the binding problem.

Perception is analyzed as a cognitive process in which information processing is used to transfer information into the mind where it is related to other information. Some psychologists propose that this processing gives rise to particular mental states (cognitivism) whilst others envisage a direct path back into the external world in the form of action (radical behaviourism). Behaviourists such as John B. Watson and B.F. Skinner have proposed that perception acts largely as a process between a stimulus and a response but have noted that Gilbert Ryle's "ghost in the machine of the brain" still seems to exist. "The objection to inner states is not that they do not exist, but that they are not relevant in a functional analysis".[6] This view, in which experience is thought to be an incidental by-product of information processing, is known as epiphenomenalism.

Contrary to the behaviouralist approach to understanding the elements of cognitive processes, gestalt psychology sought to understand their organization as a whole, studying perception as a process of figure and ground.

Philosophical accounts of perception

Important philosophical problems derive from the epistemology of perception—how we can gain knowledge via perception—such as the question of the nature of qualia.[7] Within the biological study of perception naive realism is unusable.[8] However, outside biology modified forms of naive realism are defended. Thomas Reid, the eighteenth-century founder of the Scottish School of Common Sense, formulated the idea that sensation was composed of a set of data transfers but also declared that there is still a direct connection between perception and the world. This idea, called direct realism, has again become popular in recent years with the rise of postmodernism.

The succession of data transfers involved in perception suggests that sense data are somehow available to a perceiving subject that is the substrate of the percept. Indirect realism, the view held by John Locke and Nicolas Malebranche, proposes that we can only be aware of mental representations of objects. However, this may imply an infinite regress (a perceiver within a perceiver within a perceiver...), though a finite regress is perfectly possible.[9] It also assumes that perception is entirely due to data transfer and information processing, an argument that can be avoided by proposing that the percept does not depend wholly upon the transfer and rearrangement of data. This still involves basic ontological issues of the sort raised by Leibniz[10] Locke, Hume, Whitehead and others, which remain outstanding particularly in relation to the binding problem, the question of how different perceptions (e.g. color and contour in vision) are "bound" to the same object when they are processed by separate areas of the brain.

Indirect realism (representational views) provides an account of issues such as perceptual contents,[11][12] qualia, dreams, imaginings, hallucinations, illusions, the resolution of binocular rivalry, the resolution of multistable perception, the modelling of motion that allows us to watch TV, the sensations that result from direct brain stimulation, the update of the mental image by saccades of the eyes and the referral of events backwards in time. Direct realists must either argue that these experiences do not occur or else refuse to define them as perceptions.

Idealism holds that reality is limited to mental qualities while skepticism challenges our ability to know anything outside our minds. One of the most influential proponents of idealism was George Berkeley who maintained that everything was mind or dependent upon mind. Berkeley's idealism has two main strands, phenomenalism in which physical events are viewed as a special kind of mental event and subjective idealism. David Hume is probably the most influential proponent of skepticism.

A fourth theory of perception in opposition to naive realism, enactivism, attempts to find a middle path between direct realist and indirect realist theories, positing that cognition arises as a result of the dynamic interplay between an organism's sensory-motor capabilities and its environment. Instead of seeing perception as a passive process determined entirely by the features of an independently existing world, enactivism suggests that organism and environment are structurally coupled and co-determining. The theory was first formalized by Francisco Varela, Evan Thompson, and Eleanor Rosch in "The Embodied Mind".[13]

Spatial representation

An aspect of perception that is common to both realists and anti-realists is the idea of mental or perceptual space. David Hume concluded that things appear extended because they have attributes of colour and solidity. A popular modern philosophical view is that the brain cannot contain images so our sense of space must be due to the actual space occupied by physical things. However, as René Descartes noticed, perceptual space has a projective geometry, things within it appear as if they are viewed from a point. The phenomenon of perspective was closely studied by artists and architects in the Renaissance, who relied mainly on the 11th century polymath, Alhazen (Ibn al-Haytham), who affirmed the visibility of perceptual space in geometric structuring projections.[14][15] Mathematicians now know of many types of projective geometry such as complex Minkowski space that might describe the layout of things in perception (see Peters (2000)) and it has also emerged that parts of the brain contain patterns of electrical activity that correspond closely to the layout of the retinal image (this is known as retinotopy). How or whether these become conscious experience is still unknown (see McGinn (1995)).

See also


  1. ^ a b c d cf. BonJour, Laurence (2007): "Epistemological Problems of Perception." Stanford Encyclopedia of Philosophy, accessed 1.9.2010.
  2. ^ cf. Crane, Tim (2005): "The Problem of Perception." Stanford Encyclopedia of Philosophy, accessed 1.9.2010; Drestske, Fred (1999): "Perception." In: Robert Audi, The Cambridge Dictionary of Philosophy, Second Edition, Cambridge, Massachusetts: Cambridge University Press, pp. 654–658, here p. 656.
  3. ^ cf. Alva Noë (2006): Perception. In: Sahotra Sarkar/Jessica Pfeifer (Eds.), The Philosophy of Science: An Encyclopedia, New York: Routledge, pp. 545–550, here p. 546 ff.
  4. ^ see Moutoussis and Zeki (1997)
  5. ^ "Brain decoding: Reading minds".
  6. ^ Skinner 1953
  7. ^ Chalmers DJ. (1995) "Facing up to the hard problem of consciousness." Journal of Consciousness Studies 2, 3, 200–219
  8. ^ Smythies J. (2003) "Space, time and consciousness." Journal of Consciousness Studies 10, 3, 47–64.
  9. ^ Edwards JC. (2008) "Are our spaces made of words?" Journal of Consciousness Studies 15, 1, 63–83.
  10. ^ Woolhouse RS and Franks R. (1998) GW Leibniz, Philosophical Texts, Oxford University Press.
  11. ^ Siegel, S. (2011)."The Contents of Perception", The Stanford Encyclopedia of Philosophy (Winter 2011 Edition), Edward N. Zalta (ed.), URL = <>.
  12. ^ Siegel, S.: The Contents of Visual Experience. New York: Oxford University Press. 2010
  13. ^ Varela F, Thompson E, Rosch E (1991) "The Embodied Mind: Cognitive Science and Human Experience" MIT Press
  14. ^ Nader El-Bizri (2004). "La perception de la profondeur: Alhazen, Berkeley et Merleau-Ponty". Oriens-Occidens, CNRS. Centre National de la Recherche Scientifique. 5: 171–184.
  15. ^ Nader El-Bizri (2007). "In Defence of the Sovereignty of Philosophy: al-Baghdadi's Critique of Ibn al-Haytham's Geometrisation of Place". Arabic Sciences and Philosophy. Cambridge University Press. 17: 57–80. doi:10.1017/s0957423907000367.

Sources and further reading

  • Chalmers DJ. (1995) "Facing up to the hard problem of consciousness." Journal of Consciousness Studies 2, 3, 200–219.
  • Wikibooks: Consciousness Studies
  • BonJour, Laurence (2001). "Epistemological Problems of Perception," The Stanford Encyclopedia of Philosophy, Edward Zalta (ed.). Online text
  • Burge, Tyler (1991). "Vision and Intentional Content," in E. LePore and R. Van Gulick (eds.) John Searle and his Critics, Oxford: Blackwell.
  • Crane, Tim (2005). "The Problem of Perception," The Stanford Encyclopedia of Philosophy, Edward Zalta (ed.). Online text
  • Descartes, Rene (1641). Meditations on First Philosophy. Online text
  • Dretske, Fred (1981). Knowledge and the Flow of Information, Oxford: Blackwell.
  • Evans, Gareth (1982). The Varieties of Reference, Oxford: Clarendon Press.
  • Flynn, Bernard (2004). "Maurice Merleau-Ponty," The Stanford Encyclopedia of Philosophy, Edward Zalta (ed.). Online text
  • Hume, David (1739–40). A Treatise of Human Nature: Being An Attempt to Introduce the Experimental Method of Reasoning Into Moral Subjects. Online text
  • Kant, Immanuel (1781). Critique of Pure Reason. Norman Kemp Smith (trans.) with preface by Howard Caygill, Palgrave Macmillan. Online text
  • Lacewing, Michael (unpublished). "Phenomenalism." Online PDF
  • Locke, John (1689). An Essay Concerning Human Understanding. Online text
  • McCreery, Charles (2006). "Perception and Hallucination: the Case for Continuity." Philosophical Paper No. 2006-1. Oxford: Oxford Forum. Online PDF
  • McDowell, John, (1982). "Criteria, Defeasibility, and Knowledge," Proceedings of the British Academy, pp. 455–79.
  • McDowell, John, (1994). Mind and World, Cambridge, Massachusetts: Harvard University Press.
  • McGinn, Colin (1995). "Consciousness and Space," In Conscious Experience, Thomas Metzinger (ed.), Imprint Academic. Online text
  • Mead, George Herbert (1938). "Mediate Factors in Perception," Essay 8 in The Philosophy of the Act, Charles W. Morris with John M. Brewster, Albert M. Dunham and David Miller (eds.), Chicago: University of Chicago, pp. 125–139. Online text
  • Moutoussis, K. and Zeki, S. (1997). "A Direct Demonstration of Perceptual Asynchrony in Vision," Proceedings of the Royal Society of London, Series B: Biological Sciences, 264, pp. 393–399.
  • Noe, Alva/Thompson, Evan T.: Vision and Mind: Selected Readings in the Philosophy of Perception, Cambridge: MIT Press, 2002.
  • Peacocke, Christopher (1983). Sense and Content, Oxford: Oxford University Press.
  • Peters, G. (2000). "Theories of Three-Dimensional Object Perception - A Survey," Recent Research Developments in Pattern Recognition, Transworld Research Network. Online text
  • Putnam, Hilary (1999). The Threefold Cord, New York: Columbia University Press.
  • Read, Czerne (unpublished). "Dreaming in Color." Online text
  • Russell, Bertrand (1912). The Problems of Philosophy, London: Williams and Norgate; New York: Henry Holt and Company. Online text
  • Shoemaker, Sydney (1990). "Qualities and Qualia: What's in the Mind?" Philosophy and Phenomenological Research 50, Supplement, pp. 109–31.
  • Siegel, Susanna (2005). "The Contents of Perception," The Stanford Encyclopedia of Philosophy, Edward Zalta (ed.). Online text
  • Tong, Frank (2003). "Primary Visual Cortex and Visual Awareness," Nature Reviews, Neuroscience, Vol 4, 219. Online text
  • Tye, Michael (2000). Consciousness, Color and Content, Cambridge, Massachusetts: MIT Press.
  • Infoactivity Genesis of perception investigation

External links

Australian philosophy

Australian philosophy refers to the philosophical tradition of the people of Australia and of its citizens abroad.

Critical realism

Critical realism may refer to:

Critical realism (philosophy of perception), a perspective that states that some sense-data are accurate to external objects

Critical realism (philosophy of the social sciences), philosophical approach associated with Roy Bhaskar

Theological critical realism, a term used in the religion–science interface community

Social realism, particularly applied to art

Critical realism (philosophy of perception)

In the philosophy of perception, critical realism is the theory that some of our sense-data (for example, those of primary qualities) can and do accurately represent external objects, properties, and events, while other of our sense-data (for example, those of secondary qualities and perceptual illusions) do not accurately represent any external objects, properties, and events. Put simply, critical realism highlights a mind-dependent aspect of the world that reaches to understand (and comes to an understanding of) the mind-independent world.

Danish philosophy

Danish philosophy has a long tradition as part of Western philosophy.

Perhaps the most influential Danish philosopher was Søren Kierkegaard, the creator of Christian existentialism, which inspired the philosophical movement of Existentialism. Kierkegaard had a few Danish followers, including Harald Høffding, who later in his life moved on to join the movement of positivism. Among Kierkegaard's other followers include Jean-Paul Sartre who was impressed with Kierkegaard's views on the individual, and Rollo May, who helped create humanistic psychology.

Direct and indirect realism

The question of direct or naïve realism, as opposed to indirect or representational realism, arises in the philosophy of perception and of mind out of the debate over the nature of conscious experience; the epistemological question of whether the world we see around us is the real world itself or merely an internal perceptual copy of that world generated by neural processes in our brain.

Naïve realism is known as direct realism when developed to counter indirect or representative realism, also known as epistemological dualism, the philosophical position that our conscious experience is not of the real world itself but of an internal representation, a miniature virtual-reality replica of the world.

Indirect realism is broadly equivalent to the accepted view of perception in natural science that states that we do not and cannot perceive the external world as it really is but know only our ideas and interpretations of the way the world is. Representationalism is one of the key assumptions of cognitivism in psychology. The representational realist would deny that "first-hand knowledge" is a coherent concept, since knowledge is always via some means. Our ideas of the world are interpretations of sensory input derived from an external world that is real (unlike the standpoint of idealism, which holds that only ideas are real, but mind-independent things are not).

The main alternative to representationalism is anti-representationalism, the view according to which perception is not a process of constructing internal representations.


Disjunctivism is a position in the philosophy of perception that rejects the existence of sense data in certain cases. The disjunction is between appearance and the reality behind the appearance "making itself perceptually manifest to someone."Veridical perceptions and hallucinations are not members of a common class of mental states or events. According to this theory, the only thing common to veridical perceptions and hallucinations is that in both cases, the subject cannot tell, via introspection, whether he is having a veridical perception or not. Disjunctivists claim this because they hold that in veridical perception, a subject's experience actually presents the external, mind-independent object of that perception. Further, they claim that in a hallucination there is no external object to be related to, nor are there sense-data to be a part of the perception. Thus, disjunctivism is a form of naive realism (also commonly known as direct realism).

Disjunctivism was first introduced to the contemporary literature by Michael Hinton, and has subsequently been associated with John McDowell. Disjunctivists often hold that an important virtue of their view is that it captures the common sense idea that perception involves a relation to objects in the world.


Broadly speaking, fallibilism (from Medieval Latin: fallibilis, "liable to err") is the philosophical claim that no belief can have justification which guarantees the truth of the belief. However, not all fallibilists believe that fallibilism extends to all domains of knowledge.

H. H. Price

Henry Habberley Price, FBA (17 May 1899 – 26 November 1984), usually cited as H. H. Price, was a Welsh philosopher, known for his work on the philosophy of perception. He also wrote on parapsychology.

Hierarchical epistemology

Hierarchical epistemology is a theory of knowledge which posits that beings have different access to reality depending on their ontological rank.

Index of philosophy of mind articles

This is a list of philosophy of mind articles.

Alan Turing

Alexius Meinong

Anomalous monism

Anthony Kenny

Arnold Geulincx

Association for the Scientific Study of Consciousness

Australian materialism

Baruch Spinoza

Biological naturalism

Brain in a vat

C. D. Broad

Chinese room



Consciousness Explained

Critical realism (philosophy of perception)

Daniel Dennett

David Hartley (philosopher)

David Kellogg Lewis

David Malet Armstrong

Direct realism

Direction of fit

Disquisitions relating to Matter and Spirit

Donald Davidson (philosopher)

Dream argument

Dualism (philosophy of mind)

Duration (Bergson)

Edmund Husserl

Eliminative materialism

Embodied philosophy

Emergent materialism

Evil demon

Exclusion principle (philosophy)

Frank Cameron Jackson

Fred Dretske

Functionalism (philosophy of mind)

G. E. M. Anscombe

Georg Henrik von Wright

George Edward Moore

Gilbert Harman

Gilbert Ryle

Gottfried Leibniz

Hard problem of consciousness

Henri Bergson

Hilary Putnam



Indefinite monism


Internalism and externalism

Intuition pump

J. J. C. Smart

Jaegwon Kim

Jerry Fodor

John Perry (philosopher)

John Searle

Karl Popper

Kendall Walton

Kenneth Allen Taylor

Ludwig Wittgenstein

Mad pain and Martian pain

Mental property

Methodological solipsism

Michael Tye (philosopher)


Mind-body dichotomy


Multiple Drafts Model

Multiple realizability

Naming and Necessity

Naïve realism


Neutral monism

Noam Chomsky

Parallelism (philosophy)

Personal identity


Philosophy of artificial intelligence

Philosophy of mind

Philosophy of perception


Pluralism (philosophy)

Privileged access

Problem of other minds

Property dualism

Psychological nominalism


Reflexive monism

René Descartes

Representational theory of mind

Richard Rorty

Ron McClamrock

Self (philosophy)

Society of Mind


Stephen Stich

Subjective idealism


Sydney Shoemaker

Tad Schmaltz

The Concept of Mind

The Meaning of Meaning

Thomas Nagel

Turing test

Type physicalism

Unconscious mind

Wilfrid Sellars

William Hirstein

William James

Information source

An information source is a person, thing, or place from which information comes, arises, or is obtained. Information souces can be known as primary or secondary. That source might then inform a person about something or provide knowledge about it. Information sources are divided into separate distinct categories, primary, secondary, tertiary, and so on.

List of epistemologists

This is a list of epistemologists, that is, people who theorize about the nature of knowledge, belief formation and the nature of justification.

List of philosophies

Philosophical schools of thought and philosophical movements.

Philosophy of mind

Philosophy of mind is a branch of philosophy that studies the ontology, nature, and relationship of the mind to the body. The mind–body problem is a paradigm issue in philosophy of mind, although other issues are addressed, such as the hard problem of consciousness, and the nature of particular mental states. Aspects of the mind that are studied include mental events, mental functions, mental properties, consciousness, the ontology of the mind, the nature of thought, and the relationship of the mind to the body.

Dualism and monism are the two central schools of thought on the mind–body problem, although nuanced views have arisen that do not fit one or the other category neatly. Dualism finds its entry into Western philosophy thanks to René Descartes in the 17th century. Substance dualists like Descartes argue that the mind is an independently existing substance, whereas property dualists maintain that the mind is a group of independent properties that emerge from and cannot be reduced to the brain, but that it is not a distinct substance.Monism is the position that mind and body are not ontologically distinct entities (independent substances). This view was first advocated in Western philosophy by Parmenides in the 5th century BCE and was later espoused by the 17th-century rationalist Baruch Spinoza. Physicalists argue that only entities postulated by physical theory exist, and that mental processes will eventually be explained in terms of these entities as physical theory continues to evolve. Physicalists maintain various positions on the prospects of reducing mental properties to physical properties (many of whom adopt compatible forms of property dualism), and the ontological status of such mental properties remains unclear. Idealists maintain that the mind is all that exists and that the external world is either mental itself, or an illusion created by the mind. Neutral monists such as Ernst Mach and William James argue that events in the world can be thought of as either mental (psychological) or physical depending on the network of relationships into which they enter, and dual-aspect monists such as Spinoza adhere to the position that there is some other, neutral substance, and that both matter and mind are properties of this unknown substance. The most common monisms in the 20th and 21st centuries have all been variations of physicalism; these positions include behaviorism, the type identity theory, anomalous monism and functionalism.Most modern philosophers of mind adopt either a reductive physicalist or non-reductive physicalist position, maintaining in their different ways that the mind is not something separate from the body. These approaches have been particularly influential in the sciences, especially in the fields of sociobiology, computer science (specifically, artificial intelligence), evolutionary psychology and the various neurosciences. Reductive physicalists assert that all mental states and properties will eventually be explained by scientific accounts of physiological processes and states. Non-reductive physicalists argue that although the mind is not a separate substance, mental properties supervene on physical properties, or that the predicates and vocabulary used in mental descriptions and explanations are indispensable, and cannot be reduced to the language and lower-level explanations of physical science. Continued neuroscientific progress has helped to clarify some of these issues; however, they are far from being resolved. Modern philosophers of mind continue to ask how the subjective qualities and the intentionality of mental states and properties can be explained in naturalistic terms.

Roderick Chisholm

Roderick Milton Chisholm (; November 27, 1916 – January 19, 1999) was an American philosopher known for his work on epistemology, metaphysics, free will, value theory, and the philosophy of perception. He was often called "the philosopher's philosopher."

Sense data

In the philosophy of perception, the theory of sense data was a popular view held in the early 20th century by philosophers such as Bertrand Russell, C. D. Broad, H. H. Price, A. J. Ayer, and G. E. Moore. Sense data are taken to be mind-dependent objects whose existence and properties are known directly to us in perception. These objects are unanalyzed experiences inside the mind, which appear to subsequent more advanced mental operations exactly as they are.

Sense data are often placed in a time and/or causality series, such that they occur after the potential unreliability of our perceptual systems yet before the possibility of error during higher-level conceptual analysis and are thus incorrigible. They are thus distinct from the 'real' objects in the world outside the mind, about whose existence and properties we often can be mistaken.

Talk of sense-data has since been largely replaced by talk of the closely related qualia. The formulation the given is also closely related. None of these terms has a single coherent and widely agreed-upon definition, so their exact relationships are unclear. One of the greatest troubling aspects to 20th century theories of sense data is its unclear rubric nature.

Tim Crane

Timothy Martin Crane (born 17 October 1962) is a philosopher and a central figure in the philosophy of mind, philosophy of perception and metaphysics. His contributions to philosophy include a defence of a non-physicalist account of the mind; a defence of the possibility of subjective facts; a defence of the thesis that perceptual experience has non-conceptual content; a psychologistic approach to the objects of thought; and a defence of the thesis that intentionality is the mark of the mental. He was the Knightbridge Professor of Philosophy at the University of Cambridge and a Fellow of Peterhouse from 2009. He is currently the Head of Department and Professor of Philosophy at Central European University.

Turkish philosophy

Turkish philosophy has long been affected by Islam and the country's proximity to Greece and ancient Greek philosophy.

Wilfrid Sellars

Wilfrid Stalker Sellars (May 20, 1912 – July 2, 1989) was an American philosopher and prominent developer of critical realism, who "revolutionized both the content and the method of philosophy in the United States".

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