100. The Five Exterior Senses: Distinction and Principle

Subscribe in Podcast App | Download Transcript

Lecture Notes

Main Topics #

• The Problem of Enumeration: Why five senses and not more? Thomas is responding to objections that would multiply senses either according to the nine categories of accidents, or according to distinctions within sensible qualities and common sensibles.
• Sensible Qualities vs. Other Accidents: The senses know accidents, but not all accidents have the power to move the senses as such. Only the third species of quality—sensible qualities—possess this power.
• Common Sensibles: Magnitude, figure, motion, rest, and number are called common sensibles because they do not move the senses primo et per se (first and as such), but rather by reason of sensible qualities.
• The Foundation Principle: Senses are distinguished by the diversity of what can act upon them from outside. Powers are distinguished by their objects; therefore, the diversity of objects that can change the senses as such determines the diversity of senses.
• Two Modes of Reception: All sensation involves forms being received, but they are received in two fundamentally different ways: natural (material) reception and spiritual (immaterial) reception.

Key Arguments #

First Objection: Multiple Categories = Multiple Senses #

• Objection: There are nine categories of accidents (besides substance). Since sense knows accidents and powers are distinguished by objects, why not nine senses corresponding to nine categories of accidents?
• Response: Not all accidents have the power to move the senses as such. The object of sense must be something that can actually alter or change the sense. Being just or unjust, possessing the ability to walk—these do not affect the senses. Only sensible qualities have this power.
• Key Principle: What moves the sense as such (per se) is what is perceived by the sense. The distinction of senses follows from this.

Second Objection: Common Sensibles vs. Proper Sensibles #

• Objection: Magnitude and figure differ more from color than sound differs from color (both are differences within the category of quality). If difference of object gives different senses, why not a separate sense for magnitude and figure?
• The Problem Clarified: Color and sound are both subdivisions of sensible qualities (the third species of quality). Magnitude falls under quantity; figure falls under quality but as a different species (habitus, or figure/shape) than sensible qualities. The difference is indeed greater.
• Response: To be fully addressed, but the issue concerns whether common sensibles move the senses with the same immediacy and per se character as proper sensibles.

Third Objection: Touch and Multiple Contrarieties #

• Objection: Touch knows many contrarieties: hot and cold, wet and dry. If one sense corresponds to one contrariety, touch should not be one sense but many.
• Status: Thomas notes this as a difficulty to be addressed in the next article.

Fourth Objection: Taste as a Kind of Touch #

• Objection: Aristotle says taste is tactus quidam (a certain kind of touch). Therefore, taste should not be distinguished as a separate sense.
• Status: Thomas notes this as a difficulty requiring further treatment.

Against Explanations via Organs or Media #

The Organ Explanation (rejected):

• Some attempt to explain the five senses by reference to diverse organs in which different elements dominate.
• Objection: Powers are not for the sake of organs; organs are for the sake of powers. Nature instituted diversity in organs because there is diversity in powers, not the other way around. The organ is like matter or a tool—it exists for the sake of the power’s activity.

The Medium Explanation (rejected as sole explanation):

• Some explain senses by reference to the medium: conjoined (like flesh in touch) or extrinsic (like air in sight and hearing).
• Objection: This is mentioned but not fully developed as inadequate; the media are attributed to senses according to what is suitable for the acts of the powers.

The Nature of Sensible Qualities Explanation (rejected as sole explanation):

• Some distinguish sensible qualities as those of simple bodies (hot, cold, wet, dry) versus complex bodies (taste), suggesting this accounts for diversity of senses.
• Objection: It is not the business of the senses to know the nature of sensible qualities—that belongs to the understanding. This approach confuses the proper domain of sense with intellect.

Thomas’s Solution #

The Principle: The reason for the number and distinction of exterior senses should be taken according to what belongs properly and per se (as such) to the senses.

The Nature of Sense: Sense is a passive power—naturally apt to be changed by exterior sensible things. Sensing is an undergoing, not an action on the object.

The Key Criterion: That which is able to change the sense from outside, as such, is what is perceived by the sense. According to the diversity of such exterior agents that can change the sense, the sensitive powers are distinguished.

Two-Fold Changing (Immutation):

• Natural (Material) Reception: The form of the agent is received in the patient according to its natural existence. The thing receiving it loses its former quality and takes on the new one as its own. Example: cool water on a stove receives heat and becomes warm.
• Spiritual (Immaterial) Reception: The form of the agent is received in the patient according to a kind of spiritual or immaterial being. The thing receiving it retains its own qualities while receiving the form of the other as belonging to the other. Example: the pupil of the eye receives the form of color without becoming colored.

Important Definitions #

Sensible Qualities (third species of quality): Qualities that have the power to alter things. These are the proper objects of the exterior senses—color, sound, smell, taste, and tactile qualities (hot/cold, wet/dry).

Common Sensibles: Accidents (magnitude, figure, motion, rest, number) that are perceived by more than one sense but do not move the senses primo et per se; they are perceived by reason of sensible qualities.

Accidental Sensibles: Things known through sensation but not as such by the sense itself. Example: the eye is not affected by sugar as sugar, but by its color (white).

Immutatio (mutation/alteration/changing): The way in which a sense is acted upon by its object.

Per se vs. per accidens: A distinction between what affects a sense as such (per se) versus incidentally (per accidens).

Examples & Illustrations #

The Shower Example: When first entering a hot shower, the water feels very hot. After a while in the water, it no longer feels as hot. This illustrates natural (material) reception: initially the skin receives the heat as belonging to the water (spiritual reception), but gradually the skin receives the heat as its own quality (natural reception), so the sensation diminishes.

The Ocean Example: When entering cold ocean water, it feels intensely cold at first. After time in the water, the cold sensation lessens as the body becomes accustomed. This demonstrates the same principle: the initial intense sensation is the water’s coldness received as other than the body’s temperature; later, the body receives that coldness as its own.

The Marble and Michelangelo: When Michelangelo sculpts a human figure from marble, the marble loses its original shape and receives the figure’s shape as its own—natural reception. When the eye perceives that same figure, it receives the shape without becoming that shape—spiritual reception. This illustrates the fundamental difference between physical alteration and sensation.

Sugar vs. Salt: The eye cannot distinguish whether a white substance is sugar or salt by sight alone, because the eye is not affected by the substance as sugar or salt, but only by its color (white). The intellect must supplement sensation to know the substance.

Questions Addressed #

Why five senses and not more? Because there are five fundamentally distinct ways that exterior sensible things can act upon the senses. The enumeration follows from the diversity of sensible qualities, each of which has a specific power to change a particular sense.

Why not a sense for every category of accidents? Because not all accidents have the power to move the senses as such. Most accidents (relation, time, place, substance) do not alter the senses. Only sensible qualities (the third species of quality) possess this power.

Why are common sensibles not separate senses? Because they do not move the senses primo et per se. Magnitude and figure are perceived only by reason of sensible qualities; they extend the sensible quality over space, but do not constitute a new primary object of sense.

Why should we not explain senses by organs, media, or the nature of sensible qualities? Because these explanations reverse the proper order: powers are prior to organs (organs serve powers); the media are attributed to senses according to suitability for the powers’ acts; and it is not the senses’ role to know the nature of qualities, but the intellect’s. The true distinction must be sought in what the senses can be changed by as such.

Notable Quotes #

“The sense is a certain passive power, which is apt, naturally apt, to be changed by some exterior sensible thing. Therefore, something exterior that’s able to change the sense is what, as such, is perceived by the sense.”

“The powers are not for the sake of the organs, but the organs are for the sake of the powers. Nature instituted a diversity in organs that they might be suitable to the diversity of the powers.”

“In some senses, there is found a spiritual immutation or reception only, as in sight. In some of them, however, with a spiritual immutation, there is also a natural one.”

“It does not belong to the senses to know the nature of these sensible qualities, but to the understanding.”

“According as the form of the one acting upon is received in the one acted upon according to a kind of spiritual being…the form of color is received in the pupil of the eye, which does not, through this, become colored.”