32. Sensing Our Sensing and Cross-Sensory Discrimination

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Lecture Notes

Main Topics #

The Problem of Sensing One’s Own Sensing #

• Can we sense that we see, or that we hear? Is this known by the external sense itself or by something internal?
• When viewing a painting in a museum, are we aware only of the painting, or also of our seeing of the painting?
• Aristotle is hesitant about reasoning to an internal sense from this phenomenon

The Problem of Cross-Sensory Discrimination #

• We discriminate between objects of different senses: white (sight) and sweet (taste), color (sight) and sound (hearing)
• Each external sense knows only its proper object: the eye knows color but not sweetness; taste knows flavor but not whiteness
• The question: how can we judge white to be different from sweet if no single sense apprehends both?
• Aristotle is more definite that this requires an internal sensory power

The Necessity of an Internal Sense (Common Sense) #

• No external sense alone can discriminate between white and sweet
• Even multiple external senses together cannot accomplish this (as Berquist’s analogies show)
• Therefore, there must be an internal sensory power that receives impressions from all external senses
• This power is called the κοινὴ αἴσθησις (common sense) or central sense
• It remains a sensory power, not reason, but it is internal rather than external

The Identity and Distinction of Sensible and Sense #

• The act of the sensible and the act of the sense are the same reality but differ in definition (λόγος)
• Analogy: my pushing a glass and the glass being pushed are the same motion named differently
• Sound in act and hearing in act come together as one event
• Sensing is fundamentally a being-acted-upon: the sensible acts upon the sense
• The sense organ receives the form of the sensible without its matter

Sensible in Potency vs. Sensible in Act #

• Sensible in potency: what is able to be sensed (e.g., sound in an empty forest, flavor in uneaten food)
• Sensible in act: what is actually affecting a sense (e.g., sound when being heard, flavor when being tasted)
• The previous philosophers confused these, thinking sensibles do not exist except when being sensed
• But the sensible in potency is not nothing; it is a real capacity
• The distinction matters for understanding whether sound exists without ears to hear it

Immaterial Reception in Sensation #

• When looking at something and then closing one’s eyes, one still sees an image (afterimage)
• Similarly, one experiences an aftertaste after swallowing food
• This shows the sense organ retains the sensible form in an immaterial way
• The form is present to the sense without the material substance of the external object

The Hierarchy of Knowledge Powers #

• From outward to inward: external senses → internal senses (common sense) → reason → will
• The external senses (especially the five outward ones) are more external
• The reason is more internal than sensation, especially external sensation
• The will (the desiring power) is even more internal than reason
• This mirrors the Trinitarian processions: the Word proceeds by understanding, the Holy Spirit by loving

Key Arguments #

Argument from the Impossibility of Separated Powers #

1. We discriminate between white and sweet
2. This discrimination is something sensible (it is a sensory act)
3. For one power to judge X different from Y, that power must know both X and Y
4. No single external sense knows both white and sweet
5. If two separated powers each knew one quality, they could not judge them different (as two people knowing only separate premises cannot syllogize together)
6. Therefore, there must be one unified internal sensory power that knows both
7. This power is the common sense

Argument from the Unity of the Sensing Act #

• If seeing were known by sight alone, then two different sensory acts would know color: one by sight (knowing color) and one by the internal sense (knowing the seeing of color)
• This creates redundancy: two powers knowing the same object
• To avoid infinite regress of powers knowing powers, the same power must know both the sensible and its own act of sensing
• Yet this creates a problem: if sight’s proper object is color, how can it know seeing (which is not color)?

Aristotle’s Two-Fold Solution #

1. First approach: There may be two kinds of seeing—one that senses color, another that senses the act of seeing
2. Second approach: Sensing the act of seeing is in a way sensing color, because seeing is the reception of color (immaterial reception)

Important Definitions #

Common Sense (κοινὴ αἴσθησις / Central Sense) #

An internal sensory power distinct from the five external senses that:

• Receives impressions from all external senses
• Compares and discriminates between their objects
• Judges sensible qualities to be different from one another
• Operates in the present moment with sensible particulars
• Remains a sensory power, not rational

Sensible in Potency (δύναμει) #

What is able to be sensed but is not currently acting upon any sense; a real capacity for being sensed (e.g., sound in the forest when no ear is present)

Sensible in Act (ἐνεργείᾳ) #

What is actually affecting a sense organ; the sensible quality in the act of acting upon sense (e.g., sound being heard, color being seen)

Acting Upon and Undergoing (or Activity and Passion) #

Two names for the same motion or event:

• Acting upon: the sensible’s perspective (the color acts upon the eye)
• Undergoing: the sense’s perspective (the eye is acted upon by color)
• They are the same reality but differ in definition (λόγος)

Examples & Illustrations #

The Museum Painting #

When sitting in a museum viewing a Hudson School landscape painting, one is aware not only of the painting itself but also, in a sensible way, of one’s own seeing of the painting. The question is whether this awareness of one’s seeing is by the eye alone or by an internal power.

The Licorice/Sugar Example #

The color (whiteness or blackness) of sugar or licorice is known by sight; the taste (sweetness) is known by taste. We discriminate these two qualities and judge them to be different, but no single external sense apprehends both.

The Spelling Analogy #

If person A knows only the letter ‘C’, person B only ‘A’, and person C only ‘T’, none can spell “cat” unless one person knows all three letters. Similarly, discrimination between white and sweet requires one unified power knowing both qualities.

The Syllogism Analogy #

If one person knows only the major premise (“Every mother is a woman”) and another knows only the minor premise (“No man is a woman”), neither can draw the conclusion. One person must know both premises to syllogize. Similarly, one power must know both terms to judge them different.

The Multiplication Analogy #

If you know only 4 and I know only 6, we cannot multiply them. One person must know both 4 and 6 to calculate the product. This illustrates why discrimination requires unified knowledge.

The Definition Analogy #

If you know a square is “quadrilateral” but nothing else, and I know it is “equilateral” and “right-angled” but nothing else, neither of us can define it completely. One person must know all the properties.

The Afterimage #

When one stares at something and then closes one’s eyes, the image persists. This shows the sense organ retains the sensible form in an immaterial way, without the matter of the external object.

The Aftertaste #

The taste of wine lingers after swallowing, demonstrating immaterial reception in the sense of taste.

The House Sounds #

When first moving to a house, one hears many sounds at night (wind, settling) that become unnoticed later. This exemplifies how we are sometimes aware of our hearing and sometimes not.

Waking in Darkness #

Waking in the middle of the night in darkness, one does not sense any color or light, yet one is aware of the lack of seeing. This suggests a sensing of one’s not-sensing.

Notable Quotes #

“The act of the sensible and of the sense are the same in one, but being is not the same for them.” — Aristotle, illustrating that sensation is a single event understood from two perspectives

“For a sensing by sight to seeing, while color, or what has color, is seeing…” — Aristotle, posing the difficulty of how sight (which knows color) can know seeing (which is not itself colored)

“The sensible in act and the sense in act are the same.” — Aristotle, establishing the identity of the sensible and sense as one motion

Questions Addressed #

How do we discriminate between objects of different senses? #

• Resolution: Through an internal sensory power (the common sense) that receives impressions from all external senses and unifies them, allowing comparison and discrimination between their objects.

Can external senses alone accomplish cross-sensory discrimination? #

• Resolution: No. Each external sense knows only its proper object. Discrimination of different objects requires one unified power that apprehends both terms being compared.

Is the common sense a rational power? #

• Resolution: No. The common sense remains a sensory power, though internal rather than external. It operates with sensible particulars in the present moment. Reason is a higher power that understands essences and universals.

What is the relationship between the sensible and the sense? #

• Resolution: They are the same event (the sensible acting upon the sense = the sense being acted upon), but they differ in definition or naming. One is called acting upon, the other undergoing, though they are one motion.

Does a sensible quality exist when not being sensed? #

• Resolution: Yes and no. In potency, the sensible exists as an ability to be sensed. In act, it exists only when actually affecting a sense. The previous philosophers confused these, thinking sensibles have no reality except when sensed in act.

How does sensation relate to material alteration? #

• Resolution: Sensation differs fundamentally from material alteration. The sense organ receives the form of the sensible without matter (immaterially). This is why the sensible form can remain in the sense organ after the external object is gone (afterimage, aftertaste).