Philosophy of perception

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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. Grey square optical illusion proof2.svg
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.

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]

Perception Organization, identification, and interpretation of sensory information in order to represent and understand the environment

Perception is the organization, identification, and interpretation of sensory information in order to represent and understand the presented information, or the environment.

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.

Metaphysics Branch of philosophy dealing with the nature of reality

Metaphysics is the branch of philosophy that examines the fundamental nature of reality, including the relationship between mind and matter, between substance and attribute, and between potentiality and actuality. The word "metaphysics" comes from two Greek words that, together, literally mean "after or behind or among [the study of] the natural". It has been suggested that the term might have been coined by a first century CE editor who assembled various small selections of Aristotle’s works into the treatise we now know by the name Metaphysics.


Categories of perception

We may categorize perception as internal or external.

Proprioception Sense of the relative position of ones own body parts and strength of effort employed in movement

Proprioception, also referred to as kinaesthesia, is the sense of self-movement and body position. It is sometimes described as the "sixth sense".

Cognitive psychology is the scientific study of mental processes such as "attention, language use, memory, perception, problem solving, creativity, and thinking". Much of the work derived from cognitive psychology has been integrated into various other modern disciplines such as Cognitive Science and of psychological study, including educational psychology, social psychology, personality psychology, abnormal psychology, developmental psychology, linguistics, and economics.

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.

Human eye mammalian eye; part of the visual organ of the human body, and move using a system of six muscles

The human eye is an organ that reacts to light and allows vision. Rod and cone cells in the retina allow conscious light perception and vision including color differentiation and the perception of depth. The human eye can differentiate between about 10 million colors and is possibly capable of detecting a single photon. The eye is part of the sensory nervous system.

Retina light-sensitive organ in the eye

The retina is the innermost, light-sensitive layer of tissue of the eye of most vertebrates and some molluscs. The optics of the eye create a focused two-dimensional image of the visual world on the retina, which translates that image into electrical neural impulses to the brain to create visual perception, the retina serving a function analogous to that of the film or image sensor in a camera.

Visual cortex

The visual cortex of the brain is that part of the cerebral cortex which processes visual information. It is located in the occipital lobe. Visual nerves run straight from the eye to the primary visual cortex to the Visual Association cortex.

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.

Sound mechanical wave that is an oscillation of pressure transmitted through a solid, liquid, or gas, composed of frequencies within the range of hearing; pressure wave, generated by vibrating structure

In physics, sound is a vibration that typically propagates as an audible wave of pressure, through a transmission medium such as a gas, liquid or solid.

Cochlea organ of the inner ear

The cochlea is the part of the inner ear involved in hearing. It is a spiral-shaped cavity in the bony labyrinth, in humans making 2 turns(full) and a 3/4(3 quarters) turn around its axis, the modiolus. A core component of the cochlea is the Organ of Corti, the sensory organ of hearing, which is distributed along the partition separating fluid chambers in the coiled tapered tube of the cochlea.

The binding problem is a term used at the interface between neuroscience, cognitive science and philosophy of mind that has multiple meanings.

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.

Information processing is the change (processing) of information in any manner detectable by an observer. As such, it is a process that describes everything that happens (changes) in the universe, from the falling of a rock to the printing of a text file from a digital computer system. In the latter case, an information processor is changing the form of presentation of that text file. Information processing may more specifically be defined in terms used by, Claude E. Shannon as the conversion of latent information into manifest information. Latent and manifest information is defined through the terms of equivocation, dissipation, and transformation.

In psychology, cognitivism is a theoretical framework for understanding the mind that gained credence in the 1950s. The movement was a response to behaviorism, which cognitivists said neglected to explain cognition. Cognitive psychology derived its name from the Latin cognoscere, referring to knowing and information, thus cognitive psychology is an information-processing psychology derived in part from earlier traditions of the investigation of thought and problem solving.

John B. Watson American psychologist

John Broadus Watson was an American psychologist who established the psychological school of behaviorism. Watson promoted a change in psychology through his address Psychology as the Behaviorist Views it, which was given at Columbia University in 1913. Through his behaviorist approach, Watson conducted research on animal behavior, child rearing, and advertising. In addition, he conducted the controversial "Little Albert" experiment and the Kerplunk experiment. Watson popularized the use of the scientific theory with behaviorism. He was also editor of Psychological Review from 1910 to 1915. A Review of General Psychology survey, published in 2002, ranked Watson as the 17th most cited psychologist of the 20th century.

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.

Gestalt psychology or gestaltism is a philosophy of mind of the Berlin School of experimental psychology. Gestalt psychology is an attempt to understand the laws behind the ability to acquire and maintain meaningful perceptions in an apparently chaotic world. The central principle of gestalt psychology is that the mind forms a global whole with self-organizing tendencies through the law of prägnanz.

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

Related Research Articles

In analytic philosophy, anti-realism is an epistemological position first articulated by British philosopher Michael Dummett. The term was coined as an argument against a form of realism Dummett saw as 'colorless reductionism'.

Epiphenomenalism is a position on the mind–body problem which holds that physical and biochemical events within the human body are causal with respect to mental events. According to this view, subjective mental events are completely dependent for their existence on corresponding physical and biochemical events within the human body and themselves have no causal efficacy on physical events. The appearance that subjective mental states influence physical events is merely an illusion. For instance, fear seems to make the heart beat faster, but according to epiphenomenalism the biochemical secretions of the brain and nervous system —not the experience of fear—is what raises the heartbeat. Because mental events are a kind of overflow that cannot cause anything physical, yet have non-physical properties, epiphenomenalism is viewed as a form of property dualism.

In philosophy, idealism is the group of metaphysical philosophies that assert that reality, or reality as humans can know it, is fundamentally mental, mentally constructed, or otherwise immaterial. Epistemologically, idealism manifests as a skepticism about the possibility of knowing any mind-independent thing. In contrast to materialism, idealism asserts the primacy of consciousness as the origin and prerequisite of material phenomena. According to this view, consciousness exists before and is the pre-condition of material existence. Consciousness creates and determines the material and not vice versa. Idealism believes consciousness and mind to be the origin of the material world and aims to explain the existing world according to these principles.

Mind Combination of cognitive faculties that provide consciousness, thinking, reasoning, perception and judgement

The mind is a set of cognitive faculties including consciousness, imagination, perception, thinking, judgement, language and memory. It is usually defined as the faculty of an entity's thoughts and consciousness. It holds the power of imagination, recognition, and appreciation, and is responsible for processing feelings and emotions, resulting in attitudes and actions.

In metaphysics, the problem of universals refers to the question of whether properties exist, and if so, what they are. Properties are qualities or relations that two or more entities have in common. The various kinds of properties, such as qualities and relations, are referred to as universals. For instance, one can imagine three cup holders on a table that have in common the quality of being circular or exemplifying circularity, or two daughters that have in common being the female offsprings of Frank. There are many such properties, such as being human, red, male or female, liquid, big or small, taller than, father of, etc. While philosophers agree that human beings talk and think about properties, they disagree on whether these universals exist in reality or merely in thought and speech.

Reality is the sum or aggregate of all that is real or existent, as opposed to that which is merely imaginary. The term is also used to refer to the ontological status of things, indicating their existence. In physical terms, reality is the totality of the universe, known and unknown. Philosophical questions about the nature of reality or existence or being are considered under the rubric of ontology, which is a major branch of metaphysics in the Western philosophical tradition. Ontological questions also feature in diverse branches of philosophy, including the philosophy of science, philosophy of religion, philosophy of mathematics, and philosophical logic. These include questions about whether only physical objects are real, whether reality is fundamentally immaterial, whether hypothetical unobservable entities posited by scientific theories exist, whether God exists, whether numbers and other abstract objects exist, and whether possible worlds exist.

Transcendental idealism Epistemology of the 18th-century German philosopher Immanuel Kant. Space and time are merely formal features of how we perceive objects, not things in themselves that exist independently of us.

Transcendental idealism is a doctrine founded by German philosopher Immanuel Kant in the 18th century. Kant's doctrine maintains that human experience of things is similar to the way they appear to us—implying a fundamentally subject-based component, rather than being an activity that directly comprehends the things as they are in themselves. The doctrine is most commonly presented as the idea that time and space are just human perceptions; they are not necessarily real concepts, just a medium through which humans internalize the universe.

A mental image or mental picture is an experience that, on most occasions, significantly resembles the experience of perceiving some object, event, or scene, but occurs when the relevant object, event, or scene is not actually present to the senses. There are sometimes episodes, particularly on falling asleep and waking up (hypnopompic), when the mental imagery, being of a rapid, phantasmagoric and involuntary character, defies perception, presenting a kaleidoscopic field, in which no distinct object can be discerned. Mental imagery can sometimes produce the same effects as would be produced by the behavior or experience imagined.

Naïve realism philosophical theory of mind

In philosophy of mind, naïve realism, also known as direct realism, common sense realism or perceptual realism, is the idea that the senses provide us with direct awareness of objects as they really are. Objects obey the laws of physics and retain all their properties whether or not there is anyone to observe them. They are composed of matter, occupy space and have properties, such as size, shape, texture, smell, taste and colour, that are usually perceived correctly.

Direct and indirect realism debate regarding corrospondence between experiences of the world and its reality

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.

In metaphysics, conceptualism is a theory that explains universality of particulars as conceptualized frameworks situated within the thinking mind. Intermediate between nominalism and realism, the conceptualist view approaches the metaphysical concept of universals from a perspective that denies their presence in particulars outside the mind's perception of them. Conceptualism is anti-realist about abstract objects, just like immanent realism is.

In metaphysics, realism about a given object is the view that this object exists in reality independently of our conceptual scheme. In philosophical terms, these objects are ontologically independent of someone's conceptual scheme, perceptions, linguistic practices, beliefs, etc.

Mind–body problem open question in philosophy of how abstract minds interact with physical bodies

The mind–body problem is a philosophical problem concerning the relationship between thought and consciousness in the human mind, and the brain as part of the physical body. It is distinct from the question of how mind and body function chemically and physiologically since that question presupposes an interactionist account of mind-body relations. This question arises when mind and body are considered as distinct, based on the premise that the mind and the body are fundamentally different in nature.

Neural correlates of consciousness Bodily components, such as electrical signals, correlating to consciousness and thinking

The neural correlates of consciousness (NCC) constitute the minimal set of neuronal events and mechanisms sufficient for a specific conscious percept. Neuroscientists use empirical approaches to discover neural correlates of subjective phenomena; that is, neural changes which necessarily and regularly correlate with a specific experience. The set should be minimal because, under the assumption that the brain is sufficient to give rise to any given conscious experience, the question is which of its components is necessary to produce it.

In the philosophy of perception, critical realism is the theory that some of our sense-data can and do accurately represent external objects, properties, and events, while other of our sense-data 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 the mind-independent world.

Extended cognition is the view that mental processes and mind extend beyond the body to include aspects of the environment in which an organism is embedded and the organism's interaction with that environment. Cognition goes beyond the manipulation of symbols to include the emergence of order and structure evolving from active engagement with the world.

Higher-order theories of consciousness postulate that consciousness consists in perceptions or thoughts about first-order mental states. In particular, phenomenal consciousness is thought to be higher-order representation of perceptual or quasi-perceptual contents, such as visual images.

Mind in eastern philosophy branch of philosophy on the nature of the mind

The study of the mind in Eastern philosophy has parallels to the Western study of the Philosophy of mind as a branch of philosophy that studies the nature of the mind. Dualism and monism are the two central schools of thought on the mind–body problem in the Western tradition, although nuanced views have arisen that do not fit one or the other category neatly. Dualism is found in both Eastern and Western traditions but its entry into Western philosophy was thanks to René Descartes in the 17th century. This article on mind in eastern philosophy deals with this subject from the standpoint of eastern philosophy which is historically strongly separated from the Western tradition and its approach to the Western philosophy of mind.


  1. 1 2 3 4 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.

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