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Anna Steppan 18/6/2020, within the course "A Journey through Philosophy and Information", facilitated by J.M.Díaz at HM)


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The intention of this article is to give the reader a deeper understanding of perception and reality. Perception refers to the organization and interpretation of the incoming information. With perception there is always the link to sensation. The incoming information stimulates our sensory organs, which then can be transported to our brain. 

The different concepts of perception will be presented on theories and simple, effective examples. The different views from different theorists will be fundamental to understand the meaning of perception.

The second topic that the article touches on is reality. ‘But how can reality as we perceive it with direct realism be exact, if we know we can perceive things that are not existing or are completely different?’ Direct realism and indirect realism, philosophers such as John Locke and David Hume will help to understand where the comprehension of reality comes from. 


Sensation specifically refers to the stimulation of the humans sensory system. 

A physical object or item stimulates our sensory organs, such as our eyes, ears, nose, tongue and skin. Sunlight might hit our retina, sound waves vibrate to our eardrum, chemicals travel around the air to our nose and tongue and objects

touch our skin. 

All the examples mentioned above are physical signals in form of stimulations. Those we have to convert because it is not something our brain can work with and understand deeply. The human system has to translate those stimulations into the language of the center of all our sensory organs, the brain. The language of our brain is neural activity. For each of our senses (seeing, hearing, smelling, tasting and touching) we have an individual process of transduction from stimulation into the neural activity.



Perception refers to the organization and interpretation of the incoming information to our brain and body. With perception there is a possibility of learning and experiencing. 

For instance, the sound of a piano and the sound of a trumpet can be identified as a different sound by human being. Each of those instruments stimulates our brain activity slightly different. The only way to identify which is which is by learning the difference between those instruments. It is by learning a particular pattern of activity. The sound waves of the trumpet are causing a pattern of neural activity that can be recognized by experience as such. 

The exact same phenomenon can be seen in vision. When light is stimulating the eyes, it is not enough for us to actually see and translate the content into our understanding of the world. We rather have to learn what we are looking at to recognize and associate an object. 


We not only take those experiences and incoming information in and interpret them but we also sometimes come to realize that we can make mistakes regarding that process. We can misinterpret those stimulations send to our brain. 

Two people that were faced with the exact same situation and its explanation, may interpret the given scenery in a completely different way. 

This phenomenon can be simply demonstrated by the Necker Cube. 

'The Necker Cube Ambiguous Figure is named after its creator, Louis Albert Necker (1786-1861), who first published the illusion in the London and Edinburgh Philosophical Magazine and Journal of Science in 1882.' (Louis Albert Necker, 1882)

The Necker cube is an ambiguous drawing. It is not specifically defined and leaves us human with a sensation that can be perceived in several plausible interpretations. 

Necker Cube

Necker Cube, a different perspective on the front panel

The front panel of the Necker cube can be identified differently from two people or even one.   

As you can see in the picture above, it is either the cube in the middle which shows the blue colored area as the front panel or as seen in the right cube. The sensation is not changing. The light pattern stimulating our eyes is exactly the same but the perception is different. How we organize the information in our system is the major factor of how we see the image. The information change can also be done at will. You can choose to see the front panel in those two different ways. You can consciously change your perception of the image. 

The perception of different objects in different ways opens up the possibility of misperceiving. The misperceiving within the Necker Cube of whether the front panel is seen in the middle picture or the one on the right is predictable. 

The idea of a misinterpretation in a predictable way is exactly how illusions work. Misperceiving an image of an illusion in a predictable way.


Plato’s allegory of the cave

Plato was an ancient Greek philosopher, the influential author of the history of philosophy, the student of Socrates and the teacher of Aristotle. 

Plato’s one big life expectancy was to help people reach a state of mind, which he referred to as ‘Eudaimonia’ or fulfillment. 

Plato’s work can be seen in thirty-six dialogues. Those dialogues are put together in different books ‘The Republic, The Symposium, The Laws, The Meno and the Apology’

The most known of them all is his book VII ‘The Republic’ and its famous ‘Allegory of the Cave’. 

'Next, said I, compare our nature in respect of education and its lack to such an experience as this. Picture men dwelling in a sort of sub-terranean cavern with a long entrance open to the light on its entire width. Conceive them as having their legs and necks fettered from childhood, so that they remain in the same spot, able to look forward only, and prevented by the fetters from turning their heads. Picture further the light from a fire burning higher up and at a distance behind them, and between the fire and the prisoners and above them a road along which a low wall has been built, as the exhibitors of puppet shows have partitions before the men themselves, above which they show the puppets.' (P. Shorey trans form Plato, 1963)

In the first passage of the ‘Allegory of the cave’ Plato describes a scenery of people living their whole life imprisoned in a cave. The understanding and the image of the outside world is not given to them as they have not experienced it yet. Neither has the sunlight played a role in their life’s. All that is visional for the inhabitants in the cave comes from the shadow of the light of the fire thrown up the walls of the cave. Since those images of shadows were the only visible illustration confronting their retina the prisoners '... would deem reality to be nothing else then the shadows of the artificial objects.' (P. Shorey trans form Plato, 1963)

Phantoms of objects perceived as reality. 

One day, one of the dwellers finds a way out of the cave and enters the world. Everything his body and mind is confronted with is accurately illuminated. The shadows of objects that he has known from the cave are now in colors, shapes and sizes. All that he has seen before was only a cheat and illusion. 'Previously he had been looking merely at phantoms; now he is nearer to the true nature of being.' (P. Shorey trans form Plato, 1963)

The enlightened man decides to leave the nature of being and returns back in the cave to educate and give knowledge to those still living in the phantom ruling ‘world’. As he returns back and tries to enlighten all the other dwellers with the knowledge of the understanding of the world outside the cave, he gets confronted with sarcasm as well as antagonism. '... and would it not been said of him that he had returned from his journey a loft with his eyes ruined and that it was not worth while even to attempt the ascent? And if it were possible to lay hands on and to kill the man who tried to release them and lead them up, would they not kill him? They certainly would, he said.' (P. Shorey trans form Plato, 1963)

The Allegory of the cave is a simile of the life of all educated people. The cave dwellers have substantial similarity with human being just before philosophy. The sunlight is referred to as reason. The social distancing of the prisoner returning back to the cave is a reflective of all the philosophers and the critical thinking of their audience towards what has been told. 

Plato states that the allegory of the cave is simply a reflection of the nature of being. He states that all human beings live their life in a shadow-ruling world. 

Our ethical mindsets drawn to us by our culture such as finding the right job, the perfect partner, making the right decisions are mostly just phantoms that were placed in our society. Shadows on the walls that we refer to as reality.

Perception is the fundamental flaw in the human design. ‘The bigotry of the nonbeliever is for me nearly as funny as the bigotry of the believer.’ – Albert Einstein


The blind men and the elephant

‘The blind men and the elephant’ is a poem written by John Godfrey Saxe in the 19thcentury. 

'It was six men of Indostan to learning much inclined,

Who went to see the Elephant (Though all of them were blind),

That each by observation might satisfy his mind.' (John Godfrey Saxe, 1872)

The scenery John Godfrey Saxe describes in his parable shows a group of blind men, who have never had the chance of vision as well as the picture or the understanding of an elephant. They were guided to an elephant and were asked to describe what an elephant is and what it may look like, simply by observation. Each of the men was only allowed to observe a certain part of the animal’s body. One of the men did an observation of the tail of the elephant and was sure that an elephant must be composed of a rope-like structure. Another man touches the side of the animal and describes his examination as a wall-like structure. The man observing the leg of the elephant concludes that its structure must contain one or multiple pillars. 

After some time the men get together and each describe their observation of the perception of the elephant. Each man describes his limited experience resulting that each description is different from one another. Each individual experience is followed by a completely different conclusion. A kind of disbelieve in the experience of the other men disseminates. 

Humans have a tendency to claim the absolute truth based on their limited, subjective experience and ignore other’s telling of truth, which in many cases might be just as right. The blindness of the men goes hand in hand with the reality of the elephant. The reality of the narrative is impacted on the perspective of perception. A seemingly absolute truth is therefore by the use of real knowledge of incomplete truth only relatively absolute, relatively true. It is rather individual and personal. 

Taking this parable as a fundament, it is said, that there must be a gap, something uncertain between perception and reality. Theorist’s state, that we all experience the uncertainty between perception and reality. We are born into a series of cultural narratives and we take those cultural, master narratives and draw out our own personal narratives. Therefore, oftentimes our personal stories are just a reflective of those master narratives that we were born into. 

Even in the hard sciences such as physics, the Heisenberg’s uncertainty principle states, that we can know one thing without knowing another. The Heisenberg’s uncertainty principle is the most misunderstood principle in physics. It expands from the quantum physics to epistemological questions. The principle asserts that you can never at the same time know the exact position and the exact speed of an object. Therefore, there is a gap between what it is that we are able to know. An uncertainty of knowledge of knowing one thing without having to know another. '...where he discusses the idea that, behind our observational data, there might still exist a hidden reality in which quantum systems have definite values for position and momentum, unaffected by the uncertainty relations. He emphatically dismisses this conception as an unfruitful and meaningless speculation, because, as he says, the aim of physics is only to describe observable data.' (Heisenberg 1927: 197) Heisenberg also refers back to epistemology and states 'One should be especially careful in using the words “reality”, “actually”, etc., since these words very often lead to statements of the type just mentioned.'  (Heisenberg 1930: 11)



The philosophy of perception is based on how human beings perceive the world. Our immediate perception and our knowledge gained through our senses within generations is what we refer to as reality. Nevertheless, many philosophers have come up with different variations of the true meaning of reality.


Direct and indirect realism

Human beings perceive the world directly as it is. What we perceive in our minds must be the external world we live in. The cognizance lets humans engage with the external world. The external existence and the perception of the mind does not show any dissimilarity. Things that be perceived are existing outside of perception. Direct realism is often termed as naïve realism. 

The aspects of ‘illusion’ and ‘hallucination’ throw a big concern to the thesis of direct realism. An illusion is an incorrect apperception of reality. Illusions appear because of a mechanism called assimilation.

An elephant with five legs.

The elephant shown in the picture above, exhibits five legs instead of four legs. The illusion of this picture plays with our sense perception. We misperceive the image. The more we let our sense of vision examine the image, the more we get the understanding of the illustration being an illusion. Not only the vision gets clearer but also does the knowledge of an elephant having normally four legs come to our mind. Nevertheless, if we would follow the idea of direct realism, we would have to commit to the idea, that we perceive the external world. We would have to agree that the elephant has five legs, just how we perceive it. 

The vision of hallucination undergoes the exact same procedure. But how can reality as we perceive it with direct realism be exact, if we know we can perceive things that are not existing or are completely different? 

Another concern of the direct realism would be the observer’s position. We perceive reality in different ways under different circumstances. How can the thesis of direct realism have direct perception if we do not have consistent perception of the world? The perception of the world changes from person to person, as well as from time to time. This leads to conclude, that the direct perception of our world only stays a thesis. 


On the other hand there is the thesis of indirect realism.

Indirect realism is also referred to as representationalism. This thesis states that we perceive the external world indirectly. Between the external world and our mind stands an intermediate. In Philosophy the intermediate is known as sense data. Sense data is a mental image of an object. The mental image reflects of the external and into our mind. 

When we examine the image of an apple, we perceive the sense data of the physical apple. The sense data of the physical apple create a variety of sensations of color and texture and smell and taste. Those qualities of an object can also be called secondary qualities. The philosopher John Locke developed an assertion of primary and secondary qualities of an object. 


'Reality is divided into primary and secondary qualities' (John Locke) within the indirect realism of the physical world. The sense data, which is positioned between our minds and the physical world, can be separated into these two categories.  

For instance, an apple is a physical object in the external world. The primary qualities of that apple would be the figure, the extension, the motion, the number and the solidity. The primary qualities of an object are mind-independent. The existence of those qualities lies in the world external for us. The secondary qualities of the apple such as color, smell, taste and sound are mind-dependent. Those qualities are ideas in our minds, which we perceive. Although they exist in our minds, they do not exist in the external object.  Locke argues, the secondary qualities that we perceive are brought to us by the primary qualities. The apples extension as well as the figure exists outside our minds, the taste and the color does not exist outside our minds. 

The existing object is a tasteless and colorless object; its extension and figure produce a perception in our minds of what we see is a round, red apple. The idea of indirect realism lets us perceive the world only indirectly. 


John Locke explains his theory with a simple but rather effective example. 

One person puts a hand in a bucket full of ice; another person puts their hand into a bucket full of hot coal. After some seconds, they each put their hand in a bucket with room temperature water. To the person having the hand in an ice bucket the room temperature water feels very hot. The person having felt the hot coal, the room temperature water feels very cold. How can it be, that the same temperature of water feels hot and cold at the same time? 

Locke explains his phenomenon shown above as a sensational occurrence. The hotness and coldness of the water does not exist. It is a sensation produced by the primary qualities into our minds. The temperature of the water must therefore just be an idea. A mental idea of those secondary qualities produced by the mind independent primary qualities. 


Although all the above may sound understandable, there has still been scepticism. The so-called secondary qualities can appear different to different minds and different times. Primary qualities do not change, they stay consistent.  

Some could argue, that might not be necessarily true. 

Primary qualities might also be inconsistent. 

David Hume explains an illustration regarding those primary qualities. The size of a table looks different whether we stand further away from it or closer. How should we then perceive the table’s extension? The table’s extension and figure looks different at different times as well as different angles.

If Locke is to be consistent, he would need to see the primary and the secondary qualities as no distinction. If we base the secondary qualities upon the fact that we perceive the qualities in different ways then we need to consider the same basis for the primary qualities.


Coming back to indirect realism and sense data. An external object does not contain any color. Certain intermediate processes project the color into our minds. Considering the metaphysics of the sense data. The object produces an image of color onto our minds. If color does not exist in our brain as well as the external object, the color then must consist in a non-material world. 

If we only perceive sense data, then we never come in contact with the external objects, the external world. If this would be the case, we must then see reality as a set of mental ideas instead of an external world we live in. 


  • Kornmeier, J. and Bach, M., 2005. The Necker cube - an ambiguous figure disambiguated in early visual processing. 8. Juni 2020
  • Plato, P. Shorey trans. from Plato: Collected Dialogues, ed. Hamilton & Cairns, Random House1963. The Allegory of the Cave – Republic VII. 8. Juni 2020
  • John Godfrey Saxe, 3. August 2016. The blind men and the elephant. 11. Juni 2020              
  • The Standford Encyclopedia of Philosophy, 8. October 2001. The Uncertainty Principle. 11. Juni 2020



  • 1Necker Cube,
  • 2Necker Cube,
  • 3The elephant illusion,



  • Jorge Luis Borges, 1942. Funes, The Memorious. 24. Mai 2020. Published on:
  • José Maria Diaz Nafria, 2011. Message in an open universe. 14. April 2020. Published on:

[For referencing style, see the guideline (3) given at the article column (on the left) and the examples of the reference section. Use a section named "REFERENCES" to list your bibliographic references. If the entry is longer than 750 words, it should be subdivided in several sections]

Entries under work

Philip Warntoft 3/5/2018, within the course "The Odysee of Philopsophy and Information" facilitated by J.M.Díaz at HM)

The intention with this article is to gain a deeper understanding regarding perception as a concept and different views of how it can be interpreted as well as the human sensory system and its impact on perception. Perception is known as the interpretation and transformation of an object into an insight supported by our senses in our human sensory system. This article will also highlight a more in depth discussion and illustrations regarding perceptual experiences as accurate or vertical perceptual experience, illusion and hallucination as well as its impact on the human brain's perception. Moreover, the importance of naïve realism and content view will be described as two particular concepts of perceptual experiences as wells as what differentiates the theories regarding each concept. Furthermore, perception will also be connected to knowledge in order to describe the one's influence on the other as well as what makes knowledge to differ from perception.

The meaning of perception

As stated in Seland (2016), perception is identified as how we interpret and transform the manifestation of an object into an insight with help of our sensory system. The human sensory system consists of five particular aspects which helps us to develop and perceive information of vision, hearing, feeling, tasting, smelling and orientation. Furthermore, in order to comprehend perception, we need to understand it as a process where we absorb information from the environment and use the perceived information so as to interrelate with our environment. Moreover, perception permits each individual to provide information with the sensory system and convert it to something meaningful as well as useful in our daily lives.

Seland (2016) further claims that for instance words are composed of singular letters that together contribute to something that each individual perceives as something special and meaningful. Also, perception is not simply essential for individuals to understand and cooperate with the environment, it is also required for our existence and safety. With the help of our sensory system, we can easily capture information, adapt the information and then act in such a way that will prevent us from being hurt. For instance, we have the ability to identify the sound on an oncoming car as well as the ability to sense the heat from a hot plate to avoid being hit by the car or burned on the plate. 

According to Millar (2014), a perpetual experience of a given item or object is when the object itself is presented to the perceiver's mind. For instance, when holding a book in front of you in your hands, the book seems to be present to you in a way it never does when deliberately think or visualise that the book will actually be in front of you. When holding the book in your hands, the book is presented to you and you have an experience of holding that specific book in your hands and nothing else. Moreover, there are two relevant as well as dominant theories of perception in order to explain the distinctive phenomenology of perceptual experience: the relational view or naïve realism and the representational or content view. There are numerous philosophers such as Crane, Hellie, Fish and Kennedy who state that individuals should admit naïve realism since it delivers a sustaining explanation of perceptual experience, while the content view can not.

The human sensory system

A sensory system is a part of our human nervous system and has the intention to PROCESSING external information. The human sensory system consists of sensory receptors which are involved and contribute to a sensory perception. The recognised parts in human sensory systems are: vision, hearing, touching, tasting and smelling. Those parts of the worlds that our receptor organs replies to are identified as receptive fields. For instance, all the parts of the world or a society that an eye can see, those parts are receptive fields. Those parts of the world or a society that we can touch, those parts are receptive fields. Shortly stated, receptive fields are those fields or parts that we can take part of with help of our human sensory system. Furthermore, research has lately not only focused on external perception processes, but also the human's ability to receive and process internal body signals. This process is known as inter perception. The intention with this internal process requires an interaction between different body states and the human's awareness of these body states in order to a decent self-regulation as well as to control your personal, inner feelings (Wikipedia, 2018).


The vision is one aspect of the human sensory system and in a numerous ways it can be considered as one of the most important receptor organ. It works like this: Light is brought up with help of our two eyes which later is sorted out on our retina. The eye's retina consists of light-sensitive cells, cones and spells that help capture external information from the outside. In this manner, the human being can perceive about intensity, colour and position regarding the incoming light which our eyes can perceive. This is a process which is a part of our sensory system and also helps to shape your own perception by seeing particular things (Wikipedia, 2018). 


Hearing (also called audition) is the human ability to perceive sound by taking part of vibrations. Frequencies which humans are capable to hear are called audio or sonic. The range in order to detecting incoming audio is considered to be between 20 Hz and 20.000 Hz. When talking about audio (or sonic) there are two particular frequencies to take into consideration. Frequencies which are higher than audio (20.000 Hz) is interpreted as ultrasonic, and frequencies which are below the audio (20 Hz) are referred as infrasonic. Those frequencies can be hard for humans to detect or at least perceive since the audio is can be too low or too high. We might detect the sound but we can not perceive it and therefore no perception of the sounds has occurred. The human hearing system consists of three particular parts: outer ears, middle ears, and inner ears. The outer ears has the responsibility to collect and filter external audio waves. The middle ears transform the pressure of the sound (delivered by the outer ears) while the inner ears produces neural signals as a respond to the incoming sound. The audio is passing through the auditory pathway which leads to the primary auditory cortex in the human brain for further process and development (Wikipedia, 2018).


Touching (also called Haptic perception) is the process and human ability to detect things by touching them. This process involves a combination of somatosensory perception (touching) of patterns on the surface on the skin and proprioception of the hands position and confirmation. It is easy for people to detect and identify objects by touching them. It is all about moving your skin over the objects outer surface or take the whole object and hold it in your hand(s). In this way, human beings can easily identify and recognise an object by only touching it. If you once have touched an object, this tends to go straight into your memory, which will make it easier for you to recognise by only touching it at a later stage. Therefore, touching has such a big impact on our perception because we can perceive something by only touching it, store the information perceived and also try to link it to something that we have touch before (Wikipedia, 2018). 


Taste is the human ability to perceive different flavours of substances, for instance food. All humans receive information (in form of flavours) with help of sensory receptors (or organs) called taste buds which are placed on the outer surface of our tongues. A tongue consists of around 10.000 taste buds which in turn consists of approximately 100-150 taste receptor cells. Those cells helps us to perceive different flavours. When talking about flavours, there are five primary flavours to perceive: Sweetness, sourness, bitterness, saltiness, and umami. However, there are other existing flavours as well, but those flavours are a combination of the previously mentioned. With help of our taste buds, we can immediately perceive different information in form of flavours that we put in our mouths. All the basic tastes that we perceive are classified as either appetitive or aversive. This depends on if the things that we sense in our mouths are harmful or beneficial to ourselves (Wikipedia, 2018). 


With help of the olfactory nerve, humans are being able to detect particular odours by using the nose to smell. The olfactory nerve consists of millions of olfactory receptors or neurons which has the intention to act as sensory signal cells. Each neuron in the olfactory nerve has a cilia with direct contact to the air. The olfactory nerve is considered to be the smell mediator which connects the smell from the air to the brain which makes us able to perceive a certain smell(s) (Wikipedia, 2018). 

Other senses

There are also other senses which are worth to take into consideration when talking about the human sensory system and perception. For instance, social perception which refers to allowing humans beings to understand other individuals and groups of their social world. Furthermore, speech perception is associated to the process by which spoken languages are heard (audio), interpreted as well as understood. It is not necessary for us to understand in order to shape our perception. For instance, a Swedish speaking person can perceive an Asian person speaking Chinese without having the necessity of understanding what the Asian person is talking about. By only detecting the audio from the Asian person, the Swedish person can perceive that the other person is talking another language. Moreover, we also talk about face perception. this refers to cognitive processes in order to handling human faces, which includes having the ability to identify a human by looking at the face and also have the ability to detect emotional expressions by looking at another person's face (Wikipedia, 2018). 

Theories of perceptual experiences

Millar (2014) claims that naïve realism and content view are two theories constantly competing regarding the structure of perceptual experiences. Millar (2014) defines an experience as a certain phenomenally conscious mental state or occasion. A phenomenon can be described as an observant happening, for instance, thunder, solar eclipse, northern lights, a hurricane, etc. The phenomenal character or phenomenology of an experience is what the experience is like for the subject. We make daily judgments by continually relying to the first-person's access of experience and compare it to our own experiences. As mentioned, experiences can be distinguished from each other due to the phenomenon of phenomenology. For example, thinking about the moon is different than from what it is to visualise seeing the moon. When you see the moon, this brings a completely different perspective on the actual object. By looking at the moon in real life, you can easily determine how the moon looks, how big it is, what shape it has, how strong it is, and so on. But just thinking about the moon, several different perceptions may arise. In your own mind, you cannot perceive the moon in such a way that does not matter the true reality. Therefore, there is an important difference between experience and perspective about the actual reality and what may be reality. In other words, your personal opinion when thinking about the moon in a reality perspective based on previous experiences and perceptions make a crucial difference compared to perceptions without any experiences.

Three types of perceptual experiences

Millar (2014) further explains that perceptual experiences are those experiences and understandings which are typical of the particular sense modalities that at any rate involve the physical things and their characteristics. These perceptual experiences are explained and presented in three particular types: An accurate/vertical perceptual experience, an illusory perceptual experience (also called illusion) and a hallucinatory perceptual experience (hallucination). An accurate- or vertical perceptual experience is identified as an exactly perception regarding the characteristics of an experience that it actually has. For instance, if you put your hand on a hot plate, you feel with your sense that the plate is hot and in the worst case scenario you burn yourself. Your perception of experience in this case will be that the plate is hot and you do not want to burn yourself since you actually know the plate's temporarily state, that it is hot. An illusory perceptual experience is when a perceived object does not have all the characteristics which are expected for that specific object. It is a false perceived reality due to numerous ambiguous sense of mind.        

Figure 1: Common example of illusory perception. 
(Source: Science and Nonduality, 2018) 

For instance, Fig. 1 shows a blue background covered in orange circles of different sizes. Or is it an orange background with blue details which intends to make the subject think that it is a blue background with orange circles? However, what is it that the image is trying to convey? How do individuals perceive the picture by just taking part of the information presented in the image? One idea may be that we perceive the image to be circulating in minimal movements, but in a reality perspective, the picture is completely stagnant. It can also be perceived as an endless downhill; or, like a circular space, filled with orange circles with a vertical pole in the middle from bottom to top. Shortly stated, we perceive the image in so many different ways that it becomes difficult for our mind to understand and determine what is a true perception of reality or illusion. The third and final type of perceptual experience is hallucinatory perceptual experience or hallucination. A hallucination involves an incorrect perception of the reality. From the subjects point of view, one can experience that you see things or objects, but in fact, it does not exists. However, it is never impossible that it exists elsewhere but not during that specific occasion and at that precise location. 

Naïve realism and content view as concepts of perceptual experiences

Naïve realism is not identified as a concept of all types of perceptual experiences. Generally, it is known as a theory of vertical experiences and illusions. A vertical experience is, according to Fieandt, Järvinen, West and Korkala (2018), defined as "the direct perception of stimuli as they exist". This corresponds to the ability of the human being to orient himself in a particularly existing need that must be stimulated. For instance, the ability to eliminate the need for food in a sense of hunger. Veridical experience or perception can also lead to an unchanged perception of a changing stimuli at human beings. In other words, people tend to perceive particular objects in the environment with relatively constant characteristics (such as colour, size, etc) as unchanged even though they actually change. As naïve realism is restricted to veridical perceptual experiences, naïve realism refers to a primitive relationship of awareness or acquaintance to certain physical things and its characteristics. The naïve realist claims that veridical perceptual experiences are in a strong sense world involving. For example, visualise that you have a book with a red cover laying on a table right in front of you. Based on the naïve realist's opinion or perception of information, your perception or perceptual experience depends on your standing in relation of acquaintance to the specific book in front of you and the redness of its cover. Since the particular book and its redness are constituents in this relational state, they also contribute to your perceptual experience of the red book. Furthermore, Millar (2014) states that by having this experience, you know that you are familiar with the book and you know that it exists in real life. Bahm (1943) compiles the theoretical approach to naïve realism as follows:

1. All the objects in question are completely independent of being existing with a subject. An object can still continue to exist even if someone has not detected it or has specific knowledge about the object itself.

2. An object consists of attributes or features which are parts of the object and together shape the identity of the object. 

3. Objects are not created or changed simply because we know them. Objects, including their qualities and characteristics are not affected merely by their being known. 

4. Objects seem as they are and are as they seem. Nothing can change and object. The reality of an object is based on how it appears to others. 

5. An object is known as it seems. There is nothing between the object itself and our knowledge of the object that change the object itself. 

6. All objects are public. This means that they can be seen and interpreted by more than one person at the same time. 

Contrariwise, content theorists argue that when someone perceives an object, either real or illusory, this individual is associated to the world and represents the world to be in a particular and specific way. Furthermore, content analysts argues that a "representational mental state or event is one with a representational content" (Millar, 2014, pp. 629). Shortly stated, the content of a mental state or event represents how the world is in a reality perspective. Content view also includes beliefs and desires. For instance, a content theorist would claim that the content of an individual's belief that the book is on the table means that the book actually is on the table. The subject's (the individual's) perceptual experience refers to the actual reality. In other words, if someone believes in something in a certain way, it means that is the way it is. Both in believes and in a reality perspective. The content view associates that we ourselves determine what is right or wrong. If we believe in something in a certain way, we should stick to that thought because that is what we claim as correct. However, content theorists further states that different opinions regarding an object can still occur even if there is a content view included or not. [I would like to read Millar, because the reality of beliefs as mental states doesn't necessarily means that the belief is correct. For Dretsky information-based believes are in direct correspondence to reality, but you haven't restrict your statement to information-based beliefs] 

Perception and knowledge 

According to Rock (1985), perception is identified as a foundation of knowledge [this is actually controversial with respect to propositional knowledge. For instance, is mathematical knowledge founded on perception? Are numbers in themselves, the infinit, zero, vectorial spaces, integrals... derived from perceptions? What about justice, friendship, love, sincerity...?]. However, it is not clarified that knowledge is considered as a foundation of perception [He clearly states the normal independence of perception, but also its affection by knowledge in certain situations of ambiguity. This is connected to what I tried to explain in the lectures: that even disregarding the physiology of perception there is an inherent ambiguity of the manifestation of an observed object through the light it scatters, and therefore different interpretations can be figured out corresponding to the same manifestation. This open character of the manifestation of an object makes, on the one hand, that perception cannot be completely autonomous in the determination of percepts; on the other, that in certain situations previous knowledge can provide the clue to solve the ambiguity and it influences perception. There are neurophysiological experiments than shown the top-down influence (or feedback from higher cortical areas) in the brain in certain situations]. Although, Rock (1985) further claims that there are two particular types of knowledge that tend to influence the perception. The first kind is known as consciously knowing and the second kind is interpreted as information stored in memory founded on past experiences. Rock believes in that the consciously knowing does not normally affect what we perceive (but there are exceptions to this rule) and that the other kind of knowledge (memory from past experiences) not only manages the recognition and interpretation but also affects the perception itself. Although, restrictions exist talking about the impact of knowledge on perception. [Philip, sorry for the confusion. The previous note in this place was an estrange fusion of earlier and later texts. I think I had to recover a version in which the text was not finished and I didn't notice it. Here it goes what I meant: "I think this latter statement is somehow contradictory with respect to the previous one -as it is now stated-, since in knowledge of the second type there is always impact on perception]

It is clear that we can not correlate our perception of what we have seen of a specific object or event based on the information that we have taken part of. Although, if knowledge does not result in an influence of perception, knowledge can still contribute in a proposal or offer that we may already be or will be fully aware of. Even if we know that the moon is motionless and that it remains unchanged, it does not prevent us to change our perception regarding the moon. For instance, if a dark cloud passes and at the same time obscures the sight of the moon, there is nothing that says we can not change our view or perception of the moon. It is highly possible that you believe that the whole moon's appearance and function is affected in this situation and that it will not be white during the daytime and shining during the nighttime anymore. Rock (1985) describes this as that perception is totally unaffected by correct information. That being said, we can claim, according to Rock, that perception is completely independent of what is true or false and it is up to the individual himself to form and shape his own perception regarding a particular object. 

It is important to be able to distinguish between knowledge and perception. Rock states that knowing stands for when someone attains a symbolic representation in form of an abstract which is not straight tangled to or founded on stimulus input. What makes us able to differentiate between knowledge and perception is that knowledge is something that is fixed and can not be changed. Certainly, more than one person can have different types of knowledge within a particular area. Either one has more or less knowledge while both have correct knowledge from a reality perspective. Or it turns out that a person is right while another one has wrong knowledge within the area of discussion. Moreover, perception is according to Rock considered to be 'stimulus bound'. This means that perception is controlled by the requirement of conformity to and support by the stimulus. 

Can knowledge influence the perception?

As mentioned earlier, it is not clarified that knowledge can be seen as a foundation of perception. However, there are moments when knowledge has the ability to affect our own perception regarding a certain state. For instance, Rock (2018) mentions an example of two squares, one of which has a transparent, vertical thin opening and the other square has a drawn line in form of a curve which is placed at the centre of the square. If the slit or the opening is too narrow, the naive observer will not perceive a figure (the curve) moving behind the first square by just looking through the thin opening. Instead, the viewer will most likely observe the figure behind to move along the split. In other words, instead of watching the figure moving behind at right angles to the vertical slit, the observer will see the line moving up and down through the narrow opening in the first square. However, if the observer from the first beginning is aware of what is happening and the person knows what the line/curve behind looks like [actually if it is a line the effect is not achieved], this will result in completely different conditions and he or she will most likely achieve the anorthoscopic effect. This leads to a change in the perception of the person. The observer still has the same view as if the event should happen spontaneously. However, the change will not occur if the conditions are such that the anorthoscopic effect is not supportable, as is the case when the figure is a straight line rather than a curved one. 

This is a classical example of how knowledge can change or influence a person's individual perception. The reason for this is that the transformation is suspicious and somehow too poor or less sufficient than it can be in order to bring to mind a certain or the favoured explanation. Therefore, only a diverse solution occurs. Nevertheless, the stimulus and particular subsidiary perceptions can maintain the preferred solution, which in this case is the most important thing  [I don't understand this]. Hence, if a person is given any hint regarding the preferred solution, it can directly be preserved by all individuals.


Scientific articles
  • Seland, D. (2016). "Perception: Recognition and Interpretation". Quality Magazin, 55(5), p.6. [Online] Deerfield, Illinois: BNP Media <> [Accessed: 9/5/2018]
  • Millar, B., 2014. The Phenomenological Problem of Perception. Philosophy and Phenomenological Research, 88(3), pp.625–654.
  • Rock, I. (1985). "Perception and Knowledge". Acta Psychologica, Vol. 59, pp. 3-22.
  • Bahm, A.J., 1943. What Is Knowledge? The Scientific Monthly, 56(3), pp.266–273.
Online sources
  • Järvinen, E., West, L., Korkala, P., Fieandt, K. (2018) "Space Perception" [Online] <> [Accessed: 15/05/2018]
  • Wikipedia. (2018). Perception. Theories of perception. Wikipedia. [Online]. Available at: [Accessed: 30/05/2018]

Incorporated entries

Whenever an entry is integrated in the article (left column) the corresponding entry is reflected in this section.

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