18. The Five Powers of the Soul and Four Grades of Life

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Lecture Notes

Main Topics #

The Five Genera of Powers #

Aristotle identifies five distinct genera (classes) of powers constituting the soul:

1. Nutritive Power (θρεπτικόν / threptikon) - The feeding and growing power; found in plants alone. Includes capacity to feed, grow, and reproduce.

2. Sensitive Power (αἰσθητικόν / aestheticon) - The sensing power; includes external senses (sight, hearing, smell, taste, touch) and internal senses.

3. Appetitive Power (ὀρεκτικόν / oreptikon) - The desiring powers; includes both sense desire and rational desire (will). Named from desire because desiring acts are more noticeable than liking, which is more fundamental.

4. Locomotive Power (κινητικόν κατὰ τόπον / kinetikon kata topon) - Power to move from place to place; found in higher animals that possess distance senses (sight, hearing, smell).

5. Intellectual/Thinking Power (διανοητικόν / dianoeikon) - The discursive power of reason; unique to humans. Related to dianoia (reasoning from one thing to another). Involves reasoning through preexistent knowledge rather than direct intuition.

The Hierarchical Ordering #

The powers are ordered such that lower powers can exist without higher ones, but not vice versa:

• Nutritive powers exist alone (plants)
• Nutritive + Sensitive exist without locomotive powers (fixed animals like sea creatures)
• Nutritive + Sensitive + Locomotive exist without thinking powers (higher animals)
• All five powers exist in humans, but intellectual power depends on the others

Four Grades of Life (Not Five) #

Although there are five powers, they organize into only four grades of life:

1. Plants - Nutritive powers only (feeding, growth, reproduction)
2. Lower Animals - Nutritive + Sensitive powers (but no locomotion)
3. Higher Animals - Nutritive + Sensitive + Locomotive powers
4. Humans - All powers including understanding and will

Why only four grades? The appetitive power does not constitute a separate grade because:

• Wherever there is sensation, pleasure/pain and desire necessarily follow
• Wherever there is understanding, will necessarily follows
• Appetite therefore accompanies both the second and fourth grades

Material and Immaterial Aspects #

Berquist explains the distinction following Thomas Aquinas:

• Material being: The body requires nutritive powers for preservation (feeding, growth)
• Immaterial being: Understanding (intellectual power) is unique to humans and non-bodily in its operations
• Middle ground: Sensing powers occupy an intermediate position—they receive forms without material alteration (the eye does not become the color it perceives)

This hierarchical structure reflects degrees of rising above mere matter, which is why the Church insists the rational soul must be the form of the body (not separate substance).

The Discursive Nature of Reason (Dianoia) #

The thinking power differs from mere understanding (nous) by its mode of operation:

• Discursive (dianoeikon): reasoning from one thing to another; knowing the unknown through the known
• Intuitive (nous): direct understanding of first principles
• Contrasted with imagination, which is free to imagine anything; reason is constrained by need to have grounds for thinking something

Naming the Powers #

Berquist notes the philosophical significance of how Aristotle names these powers:

• Nutritive power named from its operation (nourishment)
• Sensitive power named from its operation (sensing)
• Appetitive power named from desire (not liking, though liking is more fundamental)—because desire/wanting is more noticeable when what is liked is absent
• Similarly, irascible appetite named from anger because anger is most manifest, though hope and fear are also present

Key Arguments #

Why There Are Five Powers But Only Four Grades #

• The five powers do not map one-to-one onto grades of life
• The appetitive power is parasitic on the other powers; it does not emerge at a new level
• Plants have no appetite (no sensation)
• Animals with sensation necessarily have sense appetite (pleasure/pain)
• Humans with understanding necessarily have rational appetite (will)
• Therefore appetitive power appears at grades 2 and 4 but does not constitute its own grade

The Immateriality Principle and Church Teaching #

Council of Vienna (1311-1312) condemns as heretical the denial that “the substance of the rational or intellectual soul is truly and of itself the form of the human body.”

Fifth Lateran Council (1513) reaffirms this doctrine against Pomponazzi and others who claimed the intellectual soul is mortal or that a single soul is common to all humans.

Berquist notes these Church teachings reflect philosophical truth knowable by natural reason: the soul must be the form (not matter) of the body because the body only becomes capable of its operations when informed by soul.

The Five Powers as Reflecting Being and Operations #

Thomas Aquinas grounds the five powers in the fundamental structure of being:

• All living things have being (existence)
• Higher living things have two kinds of being: material and immaterial
• The five powers correspond to:
  • Material being (nutritive)
  • Immaterial reception (sensitive—receives forms without material alteration)
  • Informing disposition (appetitive—follows upon knowledge of form)
  • Operative consequence (locomotive—follows from desire)
  • Immaterial operation (intellectual—transcends matter entirely)

Important Definitions #

Threptikon (θρεπτικόν): The nutritive or feeding power; includes feeding, growing, and reproductive capacity

Aestheticon (αἰσθητικόν): The sensitive power; the power of sensing through internal and external senses

Oreptikon (ὀρεκτικόν): The appetitive or desiring power; includes sense desire and rational desire

Kinetikon kata topon (κινητικόν κατὰ τόπον): The power to move from place to place

Dianoeikon (διανοητικόν): The thinking or discursive power; reasoning that proceeds from one thing to another

Nous (νοῦς): Understanding or intellectual intuition (distinct from discursive reasoning)

Forma (Latin): Form; that by which matter becomes capable of its operations; the soul is the form of the body

Potentia (Latin): Potency; capacity or power to perform operations

Examples & Illustrations #

The Eye Analogy #

Berquist uses the eye to illustrate how the soul relates to the body as form to matter:

• The matter of the eye (flesh and blood) does not enable seeing
• The power of sight is what enables the eye to actually see
• A dead eye (lacking the power of sight) is an eye only equivocally, not in the proper sense
• Similarly, a body without soul is not truly alive—it is a body only equivocally

Distance Senses and Locomotion #

Higher animals possess distance senses (sight, hearing, smell) because they can move from place to place and need to know things at a distance. Fixed animals like sea creatures (attached to ocean floor) require only touch and taste, and thus do not develop locomotive power. This shows the purposeful ordering of powers.

Freedom vs. Constraint in Imagination and Reason #

• Imagination: Can imagine terrorists arriving, John Paul II walking through the door, etc.—essentially unconstrained
• Reason: Cannot think John Paul II will appear without reason or ground for such a thought
• This difference reflects that reasoning (discursive knowing) must proceed from something already known; imagination is free to juxtapose any images

Plants Growing Upward and Downward #

Plants demonstrate the soul’s transcendence of nature’s limitations: plants grow both upward and downward, unlike non-living things (stones fall only down, balloons rise only up). The soul orders matter toward life and reproduction in ways mere material forces cannot.

Notable Quotes #

“All knowledge that is dianoeikon is from preexistent knowledge.” — Aristotle, Posterior Analytics (cited by Berquist on discursive reasoning)

“The substance of the rational or intellectual soul is truly and of itself the form of the human body.” — Council of Vienna, 1311-1312

“Whoever shall presume to assert, defend, or obstinately hold that the rational intellectual soul is not in itself and essentially the form of the human body is to be censured as a heretic.” — Council of Vienna, defining orthodox doctrine

“An eye that doesn’t see, an ear that doesn’t hear, is an eye or an ear equivocally.” — Aristotle, De Anima (cited by Berquist on form and matter)

Questions Addressed #

Why are there five powers but only four grades of life? #

Because the appetitive power does not constitute an independent level; it necessarily accompanies both sensation (in animals) and understanding (in humans). Appetite emerges at grades 2 and 4 but does not create a new grade.

How does sensation relate to material and immaterial being? #

Sensation occupies a middle position between material and immaterial being. The eye receives shapes and colors without undergoing material alteration (the eye does not become round like the objects it sees), yet it operates through bodily organs. This shows sensation transcends mere matter while remaining dependent on bodily organs.

Why does the rational soul have to be the form of the body rather than a separate substance? #

Because the body only becomes capable of living operations (nutrition, sensation, movement, understanding) when informed by the soul. Matter alone cannot perform these acts. The soul must be that by which the body first becomes capable of life. This is why denying it is heretical according to Church teaching.

What is the difference between nous (intuition) and dianoia (discursive reasoning)? #

Nous is direct intellectual intuition (like Archimedes’ sudden understanding in the bathtub). Dianoia is reasoning that proceeds from one thing to another, requiring preexistent knowledge from which to reason. Humans possess primarily discursive reasoning; understanding of first principles requires intellectual intuition.

Why is the appetitive power named from desire rather than liking? #

Because desire/wanting is more noticeable—it is experienced when what is liked is absent. Liking is more fundamental (one desires what one likes), but desire is more manifest to consciousness. The same principle explains why the irascible appetite is named from anger: anger is the most conspicuous irascible emotion, though hope and fear are also present.