exploring the senses

INTRODUCTION
Ted Honderich defines knowledge as the principle of intellectual attainment studied by epistemology. Many philosophers from time immemorial to date have ventured into the concept of knowledge and identified different types of knowledge. Benedict Spinoza for instance identified three levels of knowledge namely;
a) First degree of knowledge which is the level of sense perception
b) Second degree of knowledge which is the level of reason and
c) Third degree of knowledge which is the intuition.

In this paper, we are going to dwell on the knowledge of the first degree of Spinoza that is sense perception, which is gained from both internal and external sensation. Our work has been divided into five parts. In the first part we have defined some of the terminologies used in sense perception. In the second part we have looked at the types of senses under the categories of external and internal, highlighting the mechanism and the role played by each category because this is the gist of this research. Part three enumerates the various views of different philosophers on the nature and validity of sense knowledge. In the fourth part we have given the problems regarding sense knowledge, followed by its value in part five, and then we concluded.

A. TERMINOLOGIES
Sense
It is the psychic power or ability by which a person or an animal receives knowledge of things in the world around them.
Sense data
From the Latin word datum data is the plural form which literally means “the given”. Used in this context, Ayer adopts the term Sense data to refer to any object of which it is conceivable that someone should be directly aware. It may be material e.g. direct sight of a tree or immaterial for instance e.g. direct sight of a reflection of one’s image in a mirror.

Sensitivity
Howard H. and Trays refer to sensitivity as the ability to react to a stimulus and to detect a difference between different stimuli.
Sensibility
Honderich uses this term to mean a set of individual or collective dispositions to emotions, attitudes and feelings.
Perception
This refers to the extraction of information about one’s environment by the senses and one’s body. Perception whether veridical or delusive, to some extent depends on the external conditions. For example the character of light may be too bright or too dim to enable clear perception to take place. Sometimes one’s physiological and psychological states may also determine the level of one’s perception. For instance the health of one’s sense organs or the emotional state one is experiencing may affect the quality of perception negatively or positively.
Sensation
This is the gist of our presentation. Kendler defines sensation as an organism’s ability to detect the presence or absence of the stimuli as well as discriminating between stimuli. This definition broadly refers to all living organisms which are capable of sensing, including human beings.
Kainz’s definition excludes other organisms and specifically refers to human beings. For him, sensation as one’s subjective awareness of the sensory stimuli or sensory environment, involves those acts and contents of knowledge which are distinct from the intellectual and conceptual ideas.
Sensation therefore is the first and absolute necessary stage in the process of acquiring knowledge by receiving sense data. It is not purely a passive act, but both physical and psychic, involving the act of sensing and the object being sensed. Let us now look at the different types of senses involved.

B. TYPES OF SENSES
Senses are divided into internal and external senses as follows;
EXTERNAL SENSES
These are organic senses which human beings have in common with animals. We call them organic senses instead of sense organs; because they are not passive, but in connection with the brain, actively perform the task of sensing as we shall see later. They are responsible for receiving particular sense objects either directly or indirectly through a medium. In our research study, we came out with five external senses. Those that receive sensory impressions directly are the senses of touch and taste, while those that receive sensory impressions through a medium are the senses of; sight, hearing, and smelling.
Unlike sensation in animals which are purely physical, in human beings acts of sensation are psychic.

Mechanism of Sensation in Acquiring Knowledge
According to Honderich, once the sense is activated to a specific impression, it becomes identified with the form of the object: it acts immanently thus performing the operation of sensing.
In the act of sensing, the stimuli must get in touch with the receptor organic sense directly or indirectly through the nervous system, thus we get the sensory phase of the perception process from various sense modalities- visual, auditory, olfactory, tactile, taste or from other sensory elements like twinges, tickles, pains, itches, thirst, hunger, feelings of sexual desire which are intrinsic mental activities.

Sensations can be of, about or directed upon the same thing yet each remains different from the other. Thus the senses can work co-jointly, yet they have an introspective mental quality that distinguishes them from one another.
From the external senses, the sense impression is the form of the object without the matter, but with the individuating conditions of matter, that is of the individual/particular, not universal.
Idealists associate sensing with perception unlike the materialists who reduce it to the physiological operations of the organs and nerves alone.
It is also worthy noting that sensations are independent of the conceptual or intellectual assent of the subject, unlike reasoning, thinking, knowing and remembering. One can sense something without necessarily knowing it. Thus sensations constitute a primitive level of mental existence at a level at which discursive thought and reason are not well developed.
Let us examine the operation of the eye as one of the organic senses in order to get a glimpse of how sensation takes place generally in all the other external senses.

The Eye
According to Kendler, The eye resembles the camera. Both admit light through adjustable diaphragms. Both have lenses through which light passes and by which an image is focused on a sensitive surface, the pupil of the eye enlarges in dim light and becomes smaller in bright light (amount of light regulation when it widens in dim light, enough light can enter and vise versa).
In the human eye, the widest opening is approximately 17 times greater than the smallest. The retina is the surface inside the eye that is sensitive to light upon which the image falls. The retina has receptor cells sensitive to light
Embedded in the retinas are two different types of receptors (light sensitive structures) called rods and cones because of their shapes. The inner portions are similar to ordinary nerve cells. Rods are more sensitive to light and thus operate in dim light. Cones operate when the light is more intense. The rods and cones convert light energy into neural impulses which are transmitted through several layers of neurons before they reach the optic nerve. Light has to pass through all the nerve layers of the retina before it reaches the rods and the cones where it is absorbed. These nerve layers are transparent, but not completely so. The cones are tightly packed in what is known us the fovea. Diagrammatically an eye looks like this;
How your Eye Works
Take a moment to locate an object around you. Do you know how you are able to see it? Would you believe that what you are actually seeing are beams of light bouncing off the object and into your eyes? It is hard to believe, but it is true. The light rays enter the eye through the cornea, which is a thick, transparent protective layer on the surface of your eye. Then the light rays pass through the pupil (the dark circle in the center of your eye) and into the lens.
When light rays pass through your pupil, the muscle called the iris (colored ring) makes the size of the pupil change depending on the amount of light that's available. You may have noticed this with your own eye if you have looked at it closely in a mirror. If there is too much light, your pupil will shrink to limit the number of light rays that enter. Likewise, if there is very little light available, the pupil will enlarge to let in as many light rays as it can. Just behind the pupil is the lens and it focuses the image through a jelly-like substance called the vitreous humor onto the back surface of the eyeball, called the retina.
The retina, which is the size of your thumbnail, is filled with approximately 150 million light-sensitive cells called rods and cones. Rods identify shapes and work best in dim light. Cones on the other hand, identify color and work best in bright light. Both of these types of cells then send the information to the brain by way of the optic nerve. The amazing thing is, when they send the image to the brain, the image is upside down! It is the brain's job to turn the image right side up and then tell you what you are looking at. The brain does this in a specific place called the visual cortex.
Other organic senses operate in the same mode that is receiving the image (form) of the object which is sent then to the brain via network of nerves to give us sense knowledge from our world.
INTERNAL SENSES
In addition to external senses, St. Thomas Aquinas discovered or talks about four internal senses, namely; Common sense, Imagination, Estimation and Memory.
1. Common Sense
This is one of the internal senses which distinguishes data of different external and internal senses.Vaske calls this sense the central sense or unitive sense because it integrates two or more cognitive aspects and makes a distinction between them.
Aristotle also calls it common sense because it is the root of the external senses.
2. Imagination
This preserves the data apprehended by the senses. This type of sense creates a picture in the mind that does not exist. Therefore, it makes people to be genius and very creative in their minds.
3. Memory
This is the power with which the data known through estimative power are preserved.Vaske has combined imagination and memory into one and has given them one name (imagination). From here he distinguishes two functions of imagination. Namely;
Reproductive and phantasy function. Let us look at them one by one.
Reproductive Function
This is responsible for recalling or representing operations whose object lies in the past as “form”. That is it re-presents past events as present- day happenings. Therefore the power of a good memory is inherent in its capacity to retrieve accurately the past happenings,

Phantasy Function
Under the direction and illumination of the intellect, phantasy is the creative use of imaginations. This combines and divides the elements of the past in a novel fashion. It is operative in dreams when a person sleeps and in day- dreams as well as in a creative use of imagination.
4. Estimation
This internal sense is also known as instinct in animals. It helps them to detect what is useful, harmless or friendly regardless of the pleasant or unpleasant character of the object. In human beings this sense helps to perceive things which are beyond any of the external senses. Vaske says that it is more pronounced in practical minds for example sales persons in business etc, than in theoretical minds of the thinkers/ philosophers.

Organs of the Internal Senses
Estimative and imaginative senses tend to depend on the cerebral cortex acting either in localized centers or the entire cortex but in specific different ways.

The role of internal senses in sense knowledge
Internal senses play a secondary role in the process of sense perception, by unifying, sorting, remembering, dividing and re- mixing and re producing the impressions/ images supplied by operations of the external senses.

In addition to the four internal senses given above, let us look at the nature of intuition and emotions as internal phenomena of sense perception.
5. Intuition
This is the immediate apprehension of objects, knowledge of a concept for example the sense perception. It can also mean the capability of knowing something using feelings even if you cannot explain that feeling. Like Kant and his intuition of universals and the mystic’s intuition of God.

6. Emotions
Vaske has presented a rich survey into the sphere of emotions as we shall see in the following episode. Emotions are psychic movements towards a sensible good or away from a sensible evil aroused through sense knowledge and accompanied by an organic change that ordinarily relies on the subject for action in a passion situation.
Different terms fall under this category though we are no going to concentrate on them due to the limitation of our scope. These include;
Feelings: These are elementary pleasure or displeasure that spontaneously follows sensory perception.
Mood: This refers to a prolonged and vague feeling of state.
Emotion: This is a complex operative function that is characterized by strong impulses for action.
Passion: refers to intense and violent emotion
Affection for affective state: This is the general way by which sensible objects makes us feel.
Sense appetite: This is the inclination/ movement toward a sensible good specified by sense knowledge. Feelings, emotions, passions, and affections are some of the appetitive operations on the sense level among human beings. Intellectual appetite is the inclination of the intellect to the good as precisely good, whether pleasant or not.
Classification of emotions
According to Aristotle and the medieval scholastics, emotions are classified according to three basic elements; that is; whether the object is estimated to be, a) a sensible good/evil, b) absent or present, c) easy to attain/avoid or difficult to attain or avoid. Therefore, emotions can be desiderative or irascible.
1. Desiderative (pleasure) Emotions
These include love, desire, and pleasure on the one hand and hate, aversion and sadness on the other. Sense love is the simple or absolute movement towards a sensible good. Desire is the movement towards a sensible good which is not yet possessed. Sense delight (pleasure) is the “rest” of the appetite in the good possessed through sense knowledge. Hate is the simple or absolute inclination away from a sensible evil. Aversion is the abhorrence or turning away from a forthcoming evil. Displeasure or sadness is the “rest” or confinement of the appetite in the evil which has actually overtaken the subject.
Love takes the primacy as the absolute in the sequence of emotions whose opposite is hate, for nothing is hated unless in opposition to the sensible good.

Aggressive (Irascible) Emotions
They are two; hope and despair in face of the difficult good:
Hope is the vehement seeking of the difficult good, while despair is the surrender of the attempt to acquire the object because of the difficulties that are estimated to be insuperable.
Fear, Daring: strenuous evil
While fear is the vehement inclination to avoid an evil that is now threatening and is difficult to avoid, daring is the vehement inclination to attack the evil that is difficult to conquer. If the sensible object which we hate and abhor becomes a threatening evil that is difficult to repel, emotions of fear and daring come into play.
Anger
This unique emotion has no contrary. It arises from an inflicted present evil that causes displeasure or pain; an urge to attack with the hope of securing a revenge. It is a strong psychic inclination to destroy the evil which is presently inflicting itself on the subject.

Diagrammatic representation of the emotional sequence

a) Simple pleasurable emotional sequence
Love --------------------- desire ----------------------- pleasure (terminal)
Hate----------------------- aversion -------------------- displeasure/ sadness (terminal)

b) Aggressive emotional sequence
Hope -------------- pleasure

Love -----------------------desire ------------------------ (despair) ------------ displeasure (sadness)

Fear -------------- pleasure

Hate---------------------- aversion --------------------- (daring)------------ displeasure

pleasure

Hate --------------------- aversion -------------------- anger -------------------- displeasure


The role of emotions in sense perception
Although emotions are highly valuable in influencing human existence positively or negatively, in epistemology, they are a hinderance generally because they generate irrational opinions and they cause us to view the universe in the mirror of our moods; now as bright, now dim etc. This arises from the fact that emotional associations seldom correspond to the reality in the external sensible world. In other words emotions, depending on their intensity emotions can lead one to have a distorted, diminished or exaggerated view of sense data. They are not always parallel in intensity to sense knowledge, thus while sensations become vivid on attending to them, emotions diminish on examining them. In addition, while sensations are directed to a particular sensible quality, emotions have no single special sense as their cause, but can be triggered off by any one or more senses or all of them. Thus emotions are strongly objective though individual.


C. DIFFERENT SCHOOLS OF THOUGHT ABOUT THE NATURE AND VALIDITY SENSE KNOWLEDGE
Sense knowledge, according to many philosophers is very limited, uncertain and sometimes false when it encounters scientific verification. In addition, even though it is very useful as the beginning of all knowledge, it cannot give us universal objective truth but particular and subjective truths. Stoics and Epicurians however, believe it as true knowledge as we shall see.
Let us turn to the views of different philosophers especially as portrayed by Omoregbe.


Plato
For Plato, true knowledge cannot be acquired through sense perception because objects of sense perception are unstable, yet true knowledge is universal, unchanging. Objects of sense perception are particular and individual, things concrete, found in this world, yet objects of true knowledge are the essence of things found in the world of forms.
Aristotle
Sensation as the act of perceiving things through the sense organs is the first step in the process of acquiring knowledge. All knowledge is acquired through sense perception or sensation. Therefore for Aristotle, the external senses are the windows by which we perceive the material world, while the internal senses depend on the contents of external senses to synthesize or re-present them in their operations. Therefore without sensation, acquisition of knowledge is impossible.
Stoics
Man begins to acquire knowledge through sense perception. They reject Plato’s doctrine of the objects of knowledge being universal, because all we know are concrete things and it is concrete things that we perceive. Therefore clear perception is the criterion of truth for them.
Epicureanism
All knowledge is sense knowledge, which is the criteria for truth, sense perception leads to the formation of concepts, which are the memory images impressed on the sense organs during perception. When one makes a mistake, the error is not due to perception, neither is it due to the concepts but to the judgments. Its wrongness or rightness should be tested according to its conformity to experience. True knowledge conforms to experience. Epicureans confuse the operations of sense perception with those of the intellect.

Patristic period—St. Augustine
Augustine as a Platonic, does not believe in the certainty of knowledge acquired through sense perception, but attributes true knowledge to the world of forms where divine illumination helps human minds to grasp the truth.
Medieval-Bonaventure
Following the Aristotelian thought – all knowledge comes from sense perception except the knowledge of God and knowledge of moral virtues. These two are not objects of sense perception but they are innate. For no impression of them comes from the material world through senses to impress itself on the sense organs.
Thomas Aquinas:
He affirms that the five external senses help the human being to perceive the material world. He affirms the presence of internal senses too as already shown above.
Modern period-------Spinoza Benedict: [idealist]
Identifies three levels of knowledge, the first degree of knowledge being sense perception, the level of reason the second, and the third the level is intuition.
Sense perception for Spinoza gives us inadequate/confused knowledge because it deals with individual objects in isolation, detaching them from their totality of which they are part.

British empiricists- John Locke
Locke highlights three levels of knowledge, intuitive knowledge, demonstrative or scientific knowledge and sensitive knowledge.
All human knowledge derives from sense perception and reflection. The immediate objects according to Locke are ideas of objects, obtained when things impress themselves on our minds, leaving images that represent them. He identifies two types of ideas. Simple ideas and complex ideas and two types of qualities namely: primary and secondary qualities.
Simple ideas are the same as secondary qualities. They are powers in things which impress themselves on our senses, leaving the representations of things [images] in us. They are not in things themselves; they include sound, colour, taste, temperature, and odour.
Complex ideas are a combination of more than one simple idea to give rise to abstract ideas. It’s these ideas which supercede particular traits in things concerning a thing. However things in themselves are not perceivable according to Locke and are therefore unknowable, but we assume the existence of a substratum that supports qualities by going beyond ideas. Primary ideas like solidity, extension, figure and motion are inseparably found in things themselves.
George Berkeley
He equates sense perception or sensation with ideas. Things exist insofar as they are perceived. He denies the reality of matter and maintains that everything in the world is an idea in the mind. All sensible objects are ideas in the mind because for them, isse est percipi [to exist is to be perceived]. Things do not go out of existence when nobody is perceiving them because God is constantly perceiving them and are always known by God.
Berkeley and Locke agree that all our knowledge is about ideas, that the objects of our knowledge are ideas [not things in themselves] but according to Locke, ideas are copies of things in our minds. And Berkeley affirms that ideas are not copies/representation, but things in themselves. Therefore he denies the existence of the material world.
Immanuel Kant
Kant agrees with the empiricists that knowledge begins with sense perception though not all knowledge arises from sense perception. However, such knowledge is limited only to phenomena (appearances) which are received by our senses. Sense data via the forms of space and time and the categories of our minds give us phenomenal knowledge. Senses cannot give us the knowledge of the noumena, (things- in- themselves). Thus knowledge of reality is unknowable.
Contemporary philosophers:
Their concern is not epistemological but rather existential to the human person.
Existentialist--- Don Miguel de Unamuno Y. Jugo.
Unamuno cites the importance of the instinct for human self preservation and self- perpetuation. For him, the importance of sight, hearing, taste, smell, feeling and others are purposely for preservation of life.
Existentialists assert that not reason alone helps us to acquire knowledge or to guide our actions and behavior but also feelings, emotions or passions since they are integral parts of our very nature.


D. PROBLEMS OF SENSE KNOWLEDGE
1. It depends so much on one’s subjective response to the stimuli or the medium of the stimuli. Abnormalities or defects in the receptor organs or the medium will greatly affect its validity.
2 Senses are imperfect, gradual and fragmentary. In here, it means that they only present to us a small part of the reality.
3. They do not go beyond the subjective world (reality). We need to go beyond the knowledge of experience to the knowledge of science and reasoning. For instance the sun seems to be moving but in reality t it is the earth which moves, a stick in a glass of water may seem bent, mirage may appear like a river on a road etc
4. Senses only orient us about the reality of the external world. They only present particular aspects of the reality which are capable of accidental errors.
5. Sensation is relative and therefore it makes it hard for us to explain and apprehend other people’s experiences.

E. THE VALUE OF SENSE KNOWLEDGE
In spite of its limitations sense knowledge is useful in many ways.
1. Sensation constitutes the foundation human existence. Without it human beings cannot survive. Besides life preservation, sensation and emotions are indispensable because without them, no human activity, motions or locomotion is possible since all knowledge begins with sense perception.
Kindler asserts that without sensitivity babies are prone to damage of their lives, since they can get hold of hot objects without feeling any pain. Therefore, changes in our bodies provided by senses are essential for our existence, self preservation, activity, motion and self-perpetuation.

2. Imagination has been usefully adopted in artistic inventions, plays, architecture and computer graphics and the like.
3. Compensation errors make rail trucks appear to converge in distance yet in reality they don’t. This knowledge has been used to produce three dimension presentations on two dimensional surfaces in motion pictures, cameras, projectors and astronomic work.
4. Illusions and distortions are the source of discovery and information, for example the laws of refraction which have been used to plan for the medium of light passing through glasses of varying densities.
5. Knowledge of the distinction between the opposition of the desiderative and aggressive emotions, for example the presence of one diminishes the other has been used by psychologists and counselors to help couples to live together in love.
6. Building attitude through repetition and overt action of emotions for perfection of individuals and animals.
7. Business companies discovered the commercial use of emotions through advertisements. By keeping the message constantly present to the audience it eventually makes an impact on them and they respond accordingly.

Conclusion
Sensation constitutes the foundation of knowledge in human existence. Without it human beings cannot survive as implied by Jugo Unamuno. Besides life preservation, sensations and emotions are indispensable because without them, no human activity, motions or locomotion is possible.
In this paper, we have ventured into the phenomena of sense knowledge. We have examined its nature from the point of view of its sources, that is internal and external senses, and we have given its nature, limitations as well as value, highlighting the views of different philosophers.