17. The Soul as Form: Definition and the Five Powers

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Lecture Notes

Main Topics #

The Definition of the Soul Through Proportions #

• Aristotle establishes the soul’s definition through proportional reasoning (proportions or likenesses)
• First proportion: Soul is to body as the ability to chop is to an axe
• Second proportion: Soul is to body as the power of sight is to the eye
• These proportions make the unknown (soul) intelligible through the known (axe, eye)
• Berquist emphasizes that proportional reasoning is fundamental to philosophical discovery and scientific advancement

The Soul as First Act, Not Second Act #

• The soul is the first act of a natural body composed of organs—the form that makes it alive
• Chopping is a second act—the operation that follows from having the form
• Matter alone cannot perform living operations; it requires the form (soul) to actualize its potential
• The body is not the act of the soul; rather, the soul is the act of the body

The Soul as Form, Not Matter #

• The phrase “that by which” (δι’ ὅ) can mean either matter/subject or form
• Example: We are healthy by health (form) and by some part of the body (matter)—two senses of “by which”
• The soul is that by which we first live, sense, move, and understand
• The soul is the λόγος (logos—account, definition, intelligible principle) and εἶδος (eidos—form, species) of the body
• Matter has operations only in potency; form actualizes these operations into act

The Five Genera (Powers) of the Soul #

1. Nutritive Power (θρεπτικόν) #

• The feeding, growing, and reproducing power
• Includes three sub-powers: nutrition, growth, and reproduction
• Found in plants alone among all living things
• All animals and humans also possess this power

2. Sensitive Power (αἰσθητικόν) #

• The sensing power
• Includes external senses (sight, hearing, smell, taste, touch)
• Found in all animals
• Presupposes the nutritive power

3. Appetitive Power (ὀρεκτικόν) #

• The desiring or wanting power
• Follows upon sensation; where there is sensation, there is pleasure and pain, hence desire
• Does not constitute a separate grade of life because it always accompanies sensation and thinking

4. Locomotive Power (κινητικόν κατὰ τόπον) #

• The power to move from place to place
• Found only in higher animals
• Presupposes sensation and the higher senses (sight, smell, hearing) that perceive things at a distance
• Not found in all animals; some are fixed in place

5. Thinking Power (διανοητικόν) #

• The discursive or reasoning power
• Unique to humans
• Characterized by the ability to know one thing through another
• Berquist notes that Aristotle uses this terminology rather than νοῦς (nous) in this context, giving a more distinct notion

Hierarchy of Powers #

• Lower powers can exist without higher ones (plants have only nutritive power)
• Higher powers cannot exist without lower ones (humans must have all lower powers to have thinking)
• The nutritive power is fundamental; all other powers presuppose it
• “Before” in the second sense applies: you can have nourishing, growth, reproduction without the other powers, but not vice versa (in mortal things)

Key Arguments #

The Axe Analogy #

• Raw materials (wood and metal) are an axe only in ability (δύναμις), not in actuality (ἐνέργεια)
• Once shaped and formed, they actually become an axe
• The form (the arrangement that makes it an axe) is what enables it to chop
• Chopping is a further act that follows from having the form
• Application: The soul is proportional to what inwardly makes a body alive and enables living operations

The Eye Analogy #

• An eye is defined as something able to see
• If it lacks the ability to see, it is not really an eye (except equivocally)
• A dead eye, painted eye, or statue’s eye are eyes only equivocally (in name only)
• The power of sight (δύναμις) is to the eye as the soul is to the body
• Application: The soul is that by which a body is alive, just as sight is that by which an eye is an eye

The Demonstration of the Soul’s Definition #

• Major premise: That by which we first live is the form of the body, not the matter
• Minor premise: The soul is that by which we first live, sense, move, and understand
• Conclusion: The soul is the form of the body
• A thing does not perform the operations of life until it has its form (soul)
• Different natures are known to be different because of what they do; a tree grows and reproduces while a stone does not—yet they have the same sun, water, and soil
• Therefore, natures are distinguished by their operations, which flow from having the proper form (soul)

The Five Senses Proportion #

• Just as some living things have all five senses while others have only some or just touch (the most necessary one), so too with the powers of the soul
• This shows another proportion in the structure of living things
• Berquist notes that Einstein emphasized the importance of recognizing deep analogies underneath apparent differences in scientific work

Important Definitions #

Soul (ψυχή - psyche) #

• The first act of a natural body composed of organs
• That by which we first live, sense, move, and understand
• The substantial form of a living body
• The principle of life in living things
• Never without a body, nor is some body, but something of a body

First Act (ἐνέργεια πρώτη) vs. Second Act (ἐνέργεια δευτέρα) #

• First act: The form or power that makes something what it is (e.g., the soul, the power of sight)
• Second act: The operation or exercise of that power (e.g., living, seeing, chopping)
• A thing must have first act before it can perform second act

Proportion (ἀναλογία - analogia) #

• The likeness of ratios
• Distinguished from ratio/λόγος (logos), which is the relation of one thing to another
• Essential for discovery in philosophy and science
• The most common way theories are found in science, according to Pierre Duhem

Logos (λόγος) and Eidos (εἶδος) #

• Logos: The account, definition, or intelligible principle of a thing; the form as it is knowable
• Eidos: Form or species; what makes something what it is
• Together they constitute the soul as the intelligible principle of the living body

Potency (δύναμις) and Act (ἐνέργεια) #

• Potency: The capacity or ability to be or do something; what is potential
• Act: The realization or actualization of that capacity; what is actual
• Matter is in potency; form actualizes it
• The soul is act; the body is in potency to the soul’s life-giving operations

Examples & Illustrations #

The Axe Example #

• Raw wood and metal are potentially an axe
• Once shaped and assembled, they actually become an axe
• The form (the arrangement) is what makes it an axe
• Chopping is what the axe does once it has its form

The Eye Example #

• A living eye has the power of sight
• A dead eye, painted eye, or statue’s eye lacks this power
• These are eyes only equivocally (in name only)
• The power of sight is to the eye as the soul is to the body

The Natural Operations Argument #

• The sun and water and soil are the same for both a tree and a stone
• Yet the tree grows and reproduces itself while the stone does not
• This shows that different natures produce different operations
• A nature manifests itself through what it does
• Therefore, the soul (as form/nature) is known by the operations of the living body

Questions Addressed #

How is the soul related to the body? #

• The soul is the form of the body, not its matter
• The soul is not in the body as a sailor in a ship (extrinsic)
• The soul is in the body as form is in matter (intrinsic and essential)
• The soul and body form a substantial unity

Why do we need proportions to understand the soul? #

• The soul is less known to us than the operations of life
• Proportions help us understand the unknown through the known
• The axe and eye proportions make the soul’s nature intelligible
• Proportional reasoning is how we discover and understand in science and philosophy

What is the difference between the soul and its operations? #

• The soul is the first act (the form that makes something alive)
• Operations are second acts (what living things do)
• A thing must have the soul before it can perform living operations
• The soul is the principle of life; operations are the manifestations of life

Why is the soul not found on the dissecting table? #

• The soul is a form, not a material part
• Forms are not material substances that can be isolated or seen
• The soul is known through its operations and effects, not through material analysis
• This does not mean the soul is immaterial in the sense of being non-existent; rather, it exists as the organizing principle of matter

How do the five powers relate to each other? #

• They form a hierarchy where each higher power presupposes lower ones
• Plants have only the nutritive power
• Animals add sensation and (in higher animals) locomotion
• Humans add the thinking power
• The appetitive power accompanies sensation and thinking but is not a separate grade of life