Week 7: Internal Senses (Aristotle and Aquinas)

Week 7: Internal senses (Aristotle and Aquinas)

• Core idea: Beyond the five external senses (sight, hearing, smell, taste, touch), there are four internal senses that coordinate and interpret sensory data:
  • Internal senses: the common/unifying sense, imagination, memory, and the estimative sense (instinct).
  • Total senses discussed: 5+4=9 senses.
  • For Aquinas and Aristotle, these internal senses are not unique to humans; higher animals exhibit them as well.

Two phenomena that motivate internal senses

1) Awareness of sensing

• When we use external senses, we are aware that we are sensing. For example:
  • If we see something, we are aware of seeing; if we hear something, we are aware of hearing.
  • This awareness does not require rational reflection; it can be a low-level awareness (e.g., a dog pricks up its ears when it hears something).
• In human experience, we can retrieve past sensory encounters later: we did sense something at the time, even if we did not consciously attend to it then.
• The point is that awareness of sensing indicates an internal power beyond the bare external sense, and this awareness has to be a sensory power with an object that is itself a sensory item.

2) Distinguishing the five proper sensibles

• We can distinguish the five external sense objects at the sensory level:
  • Examples: whiteness (vision) vs sweetness (taste).
• The five external senses alone cannot distinguish these cross-sense items (e.g., sight cannot distinguish whiteness from sweetness, since those belong to different senses).
• This cross-sensory discrimination requires an internal power that is common to all five senses: the unifying/common sense (Aristotle sometimes calls it the common sense; the speaker prefers the term unifying sense).
• Thus, there must be two powers at work: the external senses and a higher internal sense that unifies and makes cross-sensory distinctions possible.

The unifying sense (common sense)

• Purpose: to unify and be aware of the objects of all five external senses; to distinguish between them at the sensory level.
• Key characteristics:
  • It is common to all five senses and operates simultaneously with them.
  • Its object is the sensory item as present to the external senses (e.g., the rustle in the leaves as heard) rather than the raw object (e.g., the leaves themselves as a physical thing).
• How it differs from the five external senses:
  • External senses: acquire the sensory object (e.g., the rustle as a physical event).
  • Unifying sense: awareness of sensing that object (the rustle as heard) and the ability to distinguish sensory objects across senses.
• Alternative naming: unifying sense vs. common sense. The author favors “unifying sense” to avoid modern equivocations with rational/common-sense usage.
• Function during experience:
  • It is active in the here-and-now while external senses are at work.
  • It provides a true-to-reality representation of the sensed object, as long as sensing is ongoing.

Imagination

• Imagination is the familiar power that tends to operate when the corresponding sense objects are not immediately present.
• Relationship to the unifying sense:
  • The unifying sense has as its object the sensation as sensed by the external senses.
  • Imagination has as its object the same sensation but as retained/retained images, i.e., stored from past sensing.
  • Imagination piggybacks on the unifying sense: it uses the same sensory images received by the five senses but stores them for later use.
• Object of imagination vs unifying sense:
  • Unifying sense: object = sensation as sensed (e.g., the leaf rustle as heard) in real time.
  • Imagination: object = the same sensation retained as an image (sensory image across modalities: sight, sound, smell, taste, touch).
• Key difference from the unifying sense:
  • The unifying sense is typically as accurate as the five senses because it operates in real time with the object.
  • Imagination is more free-floating and can be distorted; hence it is more prone to error (e.g., daydreams, fantasies, speculations about the future).
• Implications:
  • Imagination can be a source of both great good (creativity, art, literature) and error.
  • It is crucial to bring reason to bear to check imagined contents against actual sensory reality.
• Clarification about memory vs imagination:
  • Imagination stores sense images; memory recalls those images with an added element of past-present relation (the pastness of the object).

The “reception” vs “retention” analogy (Aquinas’ water vs oak tree)

• Aquinas’ analogy helps distinguish reception and retention as governed by different principles:
  • Water receives a stone easily and quickly, with ripples; oak tree receives a stone less readily and retains an impression (dent).
  • If you strike the water or the oak with a large axe, the water’s ripples expand and quickly return to normal; the oak sustains a dent.
• Application to senses:
  • The unifying sense is like water: it receives the sensory object here-and-now.
  • Imagination is like the oak tree: it retains the sensory images for longer periods.
• Conclusion from the analogy:
  • Since reception (unifying power) and retention (imagination) require opposite principles, imagination and the unifying sense must be distinct powers.

The four internal senses and their shared object

• Core idea: All four internal senses have the same object: the sense object originally received through the five external senses, but they apprehend it under different conditions.
  • Unifying sense: object = sensation as sensed (present in real-time).
  • Imagination: object = the retained sensory image (retained version of the sensation).
  • Memory: object = sense image as encountered in the past (pastness added).
  • Estimative sense (instinct): object = the same sensory object but with value judgments (good/bad, dangerous/safe).
• How memory relates to imagination:
  • Memory piggybacks on imagination by presenting sense images with an added past-ness element.
• How imagination relates to the other senses:
  • Imagination piggybacks on the unifying sense (which piggybacks on the five external senses).
• The estimative sense adds value judgments to sensory encounters:
  • It indicates whether an object is desirable or dangerous and whether it can be acted upon.
  • It prepares the animal to act (e.g., a wolf seeing a sheep may judge it as food but then adjust thinking based on practical ability to catch it).
• Examples:
  • Sheep perceives a wolf (via sight, smell, hearing) and the estimative sense marks the wolf as dangerous.
  • A wolf perceives the sheep as desirable but may realize it cannot catch it; estimative sense factors in such calculations.
• It is important to note:
  • The estimative sense presupposes the five external senses and the unifying sense.
  • Instinct can influence contents of imagination (e.g., a dog’s image of a master could become charged with danger after a negative experience).

The brain and unity of the internal senses

• Organ of the internal senses:
  • The brain is suggested as the organ for the four internal senses (not identical to the organ of the external senses).
  • If the brain is damaged or unconscious, internal senses fail, indicating their dependence on brain substrates.
• Unity and interplay:
  • The four internal senses operate in a coordinated, intimate way, foreshadowing the unity of the later powerful faculty of intellect/reason.
• Practical implication:
  • The interactions among internal senses influence rational life and behavior, and reason can modulate sensory responses (e.g., choosing how to act toward someone despite initial estimative aversion).

Connections to broader themes and real-world relevance

• Animal cognition and behavior:
  • The internal senses explain sophisticated animal behaviors (e.g., elephants’ memory, hunting dogs’ tracking, bees’ dances conveying distance and direction).
• Human rational life:
  • The internal senses feed into, and are shaped by, rational deliberation and moral decision-making.
  • We often need to balance sensory impressions with reason and free will to act virtuously or wisely.
• Ethical and practical implications:
  • Recognizing the role of instinct and imagination can help in moral education and in understanding biases.
  • Reason should guide responses to initial sensory impressions to avoid rash or unjust actions.
• Preparatory note for next topic:
  • The unity and development of these internal senses foreshadow the single noble power of intellect or reason, which will be the focus of the next lecture.

Quick recap of key terms and relations

• External senses: 5 senses that acquire sensory data (sight, hearing, smell, taste, touch).

• Internal senses: the four powers that process, store, and evaluate sensory data (unifying sense, imagination, memory, estimative sense).

• Object progression (illustrative schema):

  • External sense object: O_e (e.g., rustle in leaves as encountered by hearing).
  • Unifying sense object: Ou = f(Oe) (the object as sensed, in real time).
  • Imagination object: Oi = Retain(Ou) (the retained sensory image).
  • Memory object: Om = Past(Oi) (the sense image as encountered in the past).
  • Estimative object: $$OE = V(Oe) ext{ with value } (good/bad)

• Organ: brain (as the likely organ of internal senses).

• Overall takeaway: The four internal senses, together with the five external senses, form an integrated system that grounds perception, memory, imagination, and action, and they prepare the route to rational deliberation and ethical life.