On the Soul

Aristotle emphasizes that a good definition of something shows not only “what it is” but also “the reason for being as it is” (159). This is what he hopes to do in his inquiry into the soul. Aristotle affirms that soul is the life-principle of living things; it is what makes them alive. Being alive includes such characteristics and activities as intellect, perception, movement, rest, nourishment, growth, and decay. Living things have these characteristics in varying degrees according to their kind; for example, plants have nourishment, growth, and decay but not intellect or perception. Only animals have perception, and only human animals have intellect. Similarly, various animals have various senses, the ones that are most appropriate to them; the most necessary sense is touch. Thus, it would appear that the soul has different parts or faculties, each one responsible for a different faculty of the animal (e.g., intellect, sense)

Aristotle discusses the faculties of the soul, which include nutrition, perception, desire, locomotion, and reason. The desiderative faculty, or appetite, goes with perception and touch; if one perceives something pleasant or touches it, one desires it. Aristotle asserts that his account of soul is good for all souls. He sees different types of soul as existing in a hierarchy, from plants all the way up to man, who alone has the faculty of intellect.

The soul is the cause of the body, in three ways: It is formal cause (that which determines the form and shape of the body), final cause (that for the sake of which the body exists), and efficient cause (that which animates and causes movement and change in the body).

Aristotle now discusses nutrition as a faculty of the soul. It is characteristic of an ensouled thing to take nourishment through food. A creature preserves its substance and existence by means of nourishment. Further, by maintaining their existence through nourishment, creatures can then reproduce their kind. The nutritive faculty of the soul, then, preserves the creature, and nourishment prepares the creature for activity. The end of nourishment is to “generate something like itself” (168).

Aristotle discusses the phenomenon of perception, in particular sense perception. Perception involves a kind of change or alteration in the animal. Something actual acts upon something potential, thus bringing it to actuality.

There are different kinds or degrees of potentiality and actuality. For example, we say that a man is potentially knowing; that is, man is by nature the sort of creature who can have knowledge. Second, we say that a man who has learned a particular subject (say, grammar) is knowing. Third, there is the man who is contemplating and using his knowledge. The third man is knowing in the truest and most actual sense; his knowledge is fully actualized. In the change from potentiality to actuality, like acts upon like, bringing it to fruition and the fulfillment of its nature. The difference between the example of knowledge and that of sense perception is that in the latter case, external sense objects are involved.

There are two puzzling questions related to perception: (1) Why is there not, in addition to the five senses, an additional sense of the senses themselves, and (2) why do the senses not produce sensation without external bodies, since the earthly elements are in the soul? Aristotle discusses the subject further later on

In this brief chapter Aristotle introduces his theory of the senses. Sense objects can be of three kinds. There are sense objects that are special to each sense and sense objects that are common to all the senses. Then, finally, there are sense objects that are incidental to the thing we perceive. (For example, we see a white object in the distance that also happens to be the son of someone we know.)

Chapter 7 deals with sight. The object of sight is the visible, which includes color, which is conveyed through light and transparency. Light changes colors from potentiality to actuality, thus making sight possible.

Sound, too, operates by potentiality and actuality. Certain objects have sound in potentiality—e.g., a musical instrument. Sound comes about by movement creating waves in the air and reaching the hearing apparatus of an animal. Thus, the potential sound in an object is made actual.

Voice is “a kind of sound of an ensouled thing” (178). Only living things, having souls, can be said to have a voice. Voice comes about from the breath, which serves two functions: to warm the body and to allow the animal to live well. Because voice is a kind of sound with meaning, it allows the creature to live well.

Human beings possess a weaker sense of smell than other animals. Other animals have a sense of smell comparable to humans’ sense of color. Like the other senses, smell occurs through a medium, such as air or water. In contrast to other animals, human beings cannot smell unless they first breath in.

Aristotle analyzes taste as being akin to touch. Like touch, and unlike the other senses, there is no medium involved in tasting; one experiences the taste object directly. The object of taste is the tasteable (including flavor), just as the object of sight is the visible (including color). Thus, flavor is to taste what color is to sight. The taste faculty is capable of receiving the full range of flavors, such as sweet, bitter, salty, sour, etc. In the tasting process the taste faculty is the potential element, which the taste object brings to actuality. Moisture is necessary to the taste process, and the taste organ is necessarily capable of receiving moisture without itself being moist.

For Aristotle, touch is a more elusive sense than the others. What is the single object of this sense, as sound is of hearing and color of sight? And is flesh the sense organ of touch, or is it something else within the animal? Aristotle solves the first problem by declaring the object of touch to be the tangible and intangible. He solves the second problem by declaring that the body (flesh) is the medium of touch and not a sense organ like the eye or the ear. Touch takes place through the body itself, not through another sense organ. Moreover, the characteristics of the body are tangible through it—such as hot and cold, dry and wet, etc.

Aristotle briefly discusses perception as a whole. In perceiving, the senses receive the forms of things without their matter. This can be compared with a wax seal: The wax receives the imprint of a ring but not its gold or bronze. Thus, when we feel the cold of snow, we do not receive the snow itself but rather its coldness.