61. The Soul's Nature: Essence, Powers, and Operations

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Lecture Notes

Main Topics #

The Threefold Division of Spiritual Substances #

Following Dionysius in the Celestial Hierarchy, Thomas divides the study of spiritual substances into three aspects:

1. Essence or Nature (τί ἐστι) - What the soul is in itself
2. Powers or Virtues (δυνάμεις/virtutes) - The soul’s abilities and capacities
3. Operations (ἐνέργειαι/operationes) - The soul’s activities and functions

Questions 75-89 follow this structure, with Question 75 specifically addressing the soul’s essence.

The Order of Knowledge vs. Order of Being #

The Apparent Paradox: Thomas presents the soul’s nature first, then powers, then operations—yet epistemologically we know the soul through its operations first.

The Resolution:

• We require some knowledge of the soul’s operations to understand its nature in a preliminary way
• Once we grasp the nature (even partially), we can then study each power and operation more distinctly and completely
• Example from De Anima: Aristotle determines that understanding is an immaterial power by reasoning from its operation (knowing all material things), but later returns to examine understanding’s operations in greater particular detail

Pedagogical Note: Some teachers (including Berquist) begin by teaching the powers first, then circle back to the essence, to avoid misconceptions about how we know the soul.

Why the Theologian Studies the Soul #

Thomas restricts theological inquiry about the soul, not studying the body except insofar as it relates to the soul, because:

• The human soul is made in the image and likeness of God
• Theology considers all things in reference to God
• By contrast, Aristotle in De Anima and natural philosophy study the body extensively (digestion, bodily organs, etc.)
• The theologian cares primarily for the soul’s spiritual dignity and relation to God

Structure of Question 75 (Seven Articles) #

Question 75 contains seven articles examining the soul’s essence:

1. Whether the soul is a body
2. Whether the human soul is subsistent
3. Whether the souls of brute animals are subsistent
4. Whether the soul is man (refuting Platonism)
5. Whether the soul is composed of matter and form
6. Whether the soul is incorruptible
7. Whether the soul is of the same species as an angel

Key Arguments #

Man’s Composite Nature #

• Man unites spiritual substance (soul) and bodily substance (body)
• According to his body, man shares more in common with beasts than angels (animals have livers, hearts, etc.)
• According to his soul, man is more like an angel
• Following Aristotle (Nicomachean Ethics X): “Something is what it is most of all”
• Therefore, man is more like an angel than a beast, because the soul is more constitutive of man than the body
• When we say of a dead person, “He is gone,” even though the body remains, we acknowledge the soul as the primary constituent

The Two Most Probable Pre-Aristotelian Opinions #

Opinion 1: Simmias’s Pythagorean View (from Plato’s Phaedo)

• Claim: The soul is the harmony or organization of the body
• Modern parallel: Biologists might say a living body is alive because of how its materials are combined and ordered (like a piano in tune vs. out of tune)
• Truth it contains: The soul is indeed a form (μορφή)
• Error it contains: Treats the soul as an accidental form (like health, shape, or arrangement) rather than a substantial form
• Problem with biologism: If we could combine the same materials in the right ratios and arrangements, we could create life—but this ignores what makes a thing substantial

Opinion 2: Socratic/Platonic View (from Phaedo)

• Claim: The soul is a complete, immaterial substance imprisoned in the body
• Truth it contains: The soul is subsistent and has being in its own right
• Error it contains: Treats the soul as a complete substance, when it is actually incomplete without the body
• Platonic problem: Implies the soul’s natural state is separation from the body

Aristotle’s Synthesis:

• The soul is a substantial form that unites the truths of both views
• It is a form (not a mere organization or accident), making the body to be alive
• It is subsistent (having a mode of being in its own right), yet incomplete without the body
• The soul is the first actuality (ἐντελέχεια/actus) of the body

Important Definitions #

• Subsistent (subsistens): Having existence in its own right, not merely as an accident dependent on another subject. The soul exists not merely in the body but as a principle of being.

• Substantial Form (forma substantialis): A form that makes something be what it is essentially (e.g., the soul makes a body to be alive and human). Distinguished from accidental form.

• Accidental Form (forma accidentalis): A form that exists only in a subject and can be lost without destroying the subject’s fundamental nature (e.g., health, color, shape, or organization). A piano remaining out of tune is still a piano.

• Complete Substance: A substance fully constituted in itself and not naturally requiring union with another (e.g., an angel, God).

• Incomplete Substance: A substance that naturally requires union with another to constitute a complete being (e.g., the human soul requires the body).

Examples & Illustrations #

The Piano Analogy: A piano in tune and a piano out of tune contain the same material parts, yet they differ in their organization and ordering. The difference is accidental (the arrangement), not substantial. This illustrates how materialism treats the soul as merely an organizational principle rather than a substantial form.

Living vs. Non-living Matter: Modern biology observes that a living body and a non-living body contain the same chemical elements (carbon, oxygen, hydrogen, nitrogen, etc.). The difference lies in how these materials are combined and organized. Yet this observation, while true, does not capture the substantial difference—the presence or absence of a soul as the form making something to be.

Dante’s Purgatorio and Plato’s Tempest: Dante represents souls as air-like substances with recognizable human shapes, which is poetically beautiful but philosophically represents the Platonic error. The soul is not a subtle body.

Notable Quotes #

“When someone dies, even the common man says, ‘he’s gone.’ So what do you mean he’s gone? The body’s still there. But when the soul’s gone, we say he’s gone.” — Berquist, illustrating that the soul is what primarily constitutes a living being

“Something is what it is most of all.” — Aristotle, Nicomachean Ethics Book X, cited by Thomas and Berquist to show that man is defined by his soul more than by his body

Questions Addressed #

How Do We Know the Soul If We Come to Know It Through Operations First? #

Resolution: The epistemological order reverses the pedagogical order.

• We gain preliminary knowledge of the soul’s nature by reasoning from its operations (e.g., understanding is immaterial because it knows all material things)
• This preliminary knowledge allows us to grasp the soul’s nature in general
• Then we return to study each power and operation in particular detail with fuller understanding
• The pedagogical presentation (essence, then powers, then operations) is not a false order—it completes what the prior knowledge began

Why Does Thomas Quote Dionysius on Three Things in Spiritual Substances? #

Answer: This is not arbitrary classification but reflects the natural structure of any substantial inquiry.

• Aristotle uses the same threefold structure in De Anima: first the essence/nature, then the powers (nutritive, sensitive, rational), then the operations
• The structure is philosophically grounded in the nature of substance itself
• One can verify this structure through other thinkers (not merely accepting Dionysius’s authority)

Why Study the Soul in Theology Rather Than Natural Philosophy? #

Answer: Different disciplines have different formal objects.

• Natural Philosophy (Aristotle in De Anima): Studies both the soul and the body extensively, including animal physiology, digestion, sense organs, etc.
• Theology (Thomas in Summa): Studies the soul primarily because it is made in God’s image and likeness; the body is considered only in relation to the soul
• The theological perspective emphasizes the soul’s spiritual dignity and its relation to God, not its biological functions

Which Philosophical View of the Soul Is Closest to Truth? #

Answer: Aristotle’s view that the soul is a substantial form that is subsistent yet incomplete synthesizes the truths in both Pythagorean and Platonic views while avoiding their errors.

• It preserves the Pythagorean insight that the soul is a form without reducing it to mere organization
• It preserves the Platonic insight that the soul is substantial without wrongly treating it as a complete substance naturally separated from the body