67. Is the Soul Man? Soul and Body Composition

Summary

This lecture examines whether the soul alone constitutes the human person (Article 4, Question 75 of Aquinas’s Summa Theologiae). Berquist argues against the Platonic position that the soul is man, using the principle that what performs all operations of a thing is that thing itself. Since sensing requires bodily change and the soul cannot perform sensing operations alone, man must be understood as a composite of soul and body, not the soul in isolation.

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Lecture Notes

Main Question #

Is the soul man?

The soul is subsistent (can exist by itself), which might suggest the soul is man
Thomas argues against this conclusion through analysis of human operations and their requirements

The Platonic Error and Aristotelian Truth #

Platonic Position: Man is the soul; the body is merely an instrument or prison for the soul.

Aristotelian-Thomistic Position: Man is a composite of soul and body; neither alone constitutes man.

Key Insight: The truth lies between the extreme positions. Both extremes have some basis in reality:

Those who say man is only soul see truth in the soul’s subsistence and intellectual operations
Those who say man is only body see truth in the body’s integral role in human operations

Fundamental Principle: “That Which Does the Operations of a Thing Is That Thing” #

This principle grounds the entire argument:

If the soul alone performed all human operations (sensing, understanding, willing), then the soul would be man
But sensing is a human operation that necessarily involves bodily change
Therefore, the soul cannot be man alone

The Argument from Sensing #

Premise 1: Sensing is manifestly an operation of man (evident from experience).

Premise 2: Sensing is not an operation proper (private) to man—it is shared with animals.

Premise 3: Sensing necessarily requires bodily change:

The eye is acted upon by color
The ear is acted upon by sound
Excessive sensory stimuli can damage sensory organs (loud sounds causing hearing loss)

Premise 4: The soul cannot perform sensing operations without the body.

Conclusion: Since man performs sensing operations, and sensing requires the body, man cannot be the soul alone. Man must be the composite of soul and body.

Why Plato Erred #

Plato’s error stemmed from:

Correctly distinguishing understanding (proper to man) from sensing (shared with animals)
Correctly recognizing both as operations of the soul
Incorrectly assuming that sensing could occur without bodily change
Concluding that since the soul performs all operations without the body, the soul is man

Key Definitions #

Proprium (Proper/Private Operation)

An operation belonging to one thing alone or to a thing distinctively
Understanding is proprium to man (distinguishes man from animals)
Sensing is not proprium to man (shared with animals)
The distinction is crucial: man’s identity is not defined by sensing alone but by his complete set of operations

Hypostasis / Persona

Latin persona: an individual substance of rational nature (Boethian definition)
Greek hypostasis: an individual substance
The soul is not a hypostasis or person because it is a part of the human species, not a complete substance
Only the composite of soul and body (or the soul after separation) constitutes a person
Note: When we pray “St. Peter, pray for us,” this is synecdoche—the soul of St. Peter is in heaven, not the complete person (who awaits resurrection)

Substantial Form vs. Complete Substance

The soul is a substantial form (gives being to the composite)
The soul is subsistent (can exist by itself)
But subsistence does not make the soul a complete substance or person
Those who said the soul is a complete substance saw part of the truth, but erred in denying it is a form

The Principle of Chief Operation #

From Aristotle (Ethics, Book IX):

“Most of all seems to be each thing that is principle or chief in it”
What is chief in a thing is said to be that thing
Example: When the ruler acts, the city is said to act
Example: When the pope canonizes someone, the Church is said to have canonized them
Similarly, the intellectual part (reason) is the chief principle in man, so sometimes reason is called “the man”
But this is synecdoche—reason is not the whole man

Understanding the Inner and Outer Man (St. Paul, 2 Corinthians 4:16) #

The Argument: “Although the outward man is corrupted, the inward man is renewed day by day; therefore the soul is the inward man; therefore the soul is man.”

Thomas’s Response:

This is synecdoche (figure of speech where the part stands for the whole)
The “inward man” refers to the intellectual part of man—called “inner” because reason is the chief principle
The “outer man” refers to the sensitive part with body—called “outer” by those detained in sensible things
Just as Aristotle says “reason more than anything else is man,” we can say the chief part “is” man without meaning the soul alone is man
Proper attribution: what the soul (the chief part) does, man is said to do

Examples Illustrating the Argument #

Sensory Damage from Excessive Stimuli:

Excessively loud sounds damage hearing (factory workers, rock concert attendees)
This proves sensing requires bodily organs and bodily change
Contrast: Understanding the greatest intelligibles (God, Trinity) makes lesser things easier to understand, not harder
This proves intellect is not bodily; it has no organ that can be damaged by its object

The Hand and Foot:

A hand or foot cannot be called a hypostasis or person
Similarly, the soul cannot be called a hypostasis
Just as the hand is a part (of the body), the soul is a part (of the human species)

Synecdoche in Daily Speech:

“He’s a brain” (meaning he’s intelligent, not that he is literally a brain)
“The toe” (nickname for a skilled kicker, referring to the distinctive part)
“Big eyes” (nickname based on a prominent feature)
These figures of speech work because some part of the thing stands out

The Truth Between Extremes #

This pattern repeats throughout Thomistic metaphysics:

On the Soul’s Nature:

Accidentalists: The soul is an accidental form (saw that soul is form but erred on type)
Substance-only thinkers: The soul is a complete substance independent of body (saw that soul is substantial but erred in denying it’s a form)
Truth: The soul is a substantial form of a body composed of matter and form

On Human Nature:

Soul-only thinkers: Man is only soul (saw that soul is subsistent but missed body’s necessity)
Body-only thinkers: Man is only body (saw body’s necessity but missed soul’s distinction)
Truth: Man is soul and body together

Reply to Second Objection: The Soul as Hypostasis #

Objection: The human soul is a particular substance (not a universal). Therefore it is a hypostasis or person.

Response: Not every particular substance is a hypostasis or person. Only a substance that has the complete nature of the species can be called a hypostasis or person.

The hand is a particular substance but not a hypostasis
The foot is a particular substance but not a hypostasis
The soul is a particular substance but not a hypostasis (it is a part of the human species)
The composite (soul and body) is what has the complete nature and constitutes a person

Theological Implication: The Assumption of Mary #

Berquist notes that when defending the Assumption of Mary, Cajetan (in his audience with Pius XII) emphasized that it was fitting for Mary herself (the complete person, not just her soul) to be assumed into heaven—given her importance and causality in salvation history. This illustrates why being a person (having the complete nature of the species) matters theologically.