119. Substance, Nature, and the Meanings of Person

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Lecture Notes

Main Topics #

The Problem of Equivocation in Key Terms #

• Substance, nature, and related terms are equivocal by reason (not by chance)
• Equivocal by reason creates connection among meanings, making confusion common and dangerous
• Example: The word “bat” equivocal by chance (flying animal vs. sports equipment) cannot mislead; but equivocal by reason can mislead easily
• Students regularly confuse the senses of “before” and “after” despite instruction
• Mixing senses of equivocal terms is the most common mistake in thinking (per Aristotle’s Sophistical Refutations)

The Multiple Meanings of Substance (οὐσία/usia) #

Aristotle distinguishes in the Metaphysics (Book V):

1. First sense: What a thing is (essence); what the definition signifies
2. Second sense: The subject or supposit (ὑποκείμενον/hypokeimenon) that subsists in the genus of substance—the individual thing
3. Common notion: A thing that exists not in another as in a subject

The Multiple Meanings of Nature (φύσις/phusis) #

Aristotle in Metaphysics Book V identifies several meanings:

1. Generation of living things (nativity)
2. The source of generation in the mother
3. The intrinsic beginning of any motion or change
4. Matter or form (since these are sources of motion)
5. The essence: What a thing is, signified by definition

English usage typically employs only the last sense (“the nature of God,” “the nature of a tree”), overlooking the etymological connection to birth and generation.

The Three Names for Individual Substance #

Thomas explains that an individual substance can be named by three terms according to different considerations:

1. Subsistence (from subsistere): Insofar as it exists by itself and not in another as in a subject

   • Things that “subsist” are those that do not exist in another
   • Applied commonly to any individual in the genus of substance (dog, tree, man)

2. Nature (res naturae): Insofar as it is an individual of some determined genus or species

   • Example: Socrates is “a thing of human nature”; a dog is “a thing of canine nature”
   • Nature is more determined than essence (essence is taken from being, which is most common)

3. Hypostasis or Substance (substantia): Insofar as it stands under accidents

   • Hypostasis etymologically means “standing under” (ὑπό + στάσις/hypo + stasis)
   • Named from its position relative to accidents, which are more sensible to us
   • Substance is named from the fact that accidents depend upon it (subsisting underneath them)

The Translation Problem: Hypostasis in Greek vs. Latin #

• Greek hypostasis etymologically corresponds to Latin substantia
• But Latin substantia also means essence or nature (what a thing is)
• Confusion arises: saying “three substances” in God could suggest three natures (tritheism/heresy)
• Solution: Use subsistence (subsistentia) to avoid equivocation when discussing divine persons
• This demonstrates the critical importance of precise terminology in theology

Person as the Perfection Term #

• Person signifies what is most perfect in nature: something subsisting in a rational nature
• More particular than hypostasis: applies only to rational (intellectual) substances
• All three names (subsistence, nature, hypostasis) can apply to any individual substance
• But person, in its strict sense, applies only to rational individuals

The Problem of Defining Singulars #

• Objection: How can a singular be defined? Definitions are universal.
• Response: While “this singular” or “that singular” cannot be defined, the common notion of singularity can be defined
• Aristotle does this in the Categories when defining first substance
• The definition of person includes the notion of individuality, even though individual Socrates is not formally defined

The Question of the Separated Soul #

• A separated soul (like Peter in heaven) is not a person
• The soul is a part of human nature
• Just as a hand or other body part is not a person, neither is a separated soul alone
• Only the composite of soul and body constitutes a person (an individual substance)
• A separated soul cannot be called a hypostasis or individual substance
• When Scripture says “Peter pray for us,” this is synecdoche (part for whole)
• Augustine notes we will enjoy seeing God even more when body and soul are reunited, as the whole is more perfect than the part

Key Arguments #

Why Substance is Named from Standing Under Accidents #

• Accidents are more sensible to us than substance itself
• We perceive color, shape, size directly; we perceive the underlying substance only through intellection
• Therefore, substance is named from its relationship to what is more known to us (accidents)
• The word itself reveals an epistemological truth: accidents are our path to understanding substance

The Insufficiency of Modern Objections to Substance #

• Bertrand Russell’s objection: “Accidents have no more need of substance than the earth needs an elephant to rest on”
• Response: What would make them accidents without substance? The term presupposes substance.
• Descartes’s confusion: Identifying substance with extension (quantity)
• Response: Is quantity the same as what a thing is? No. A man’s size changes throughout life, yet he remains the same substance.
• The common understanding confirms the distinction: size and essence are not identical

Why Accidents Are Known Before Substance #

• We see color before we understand the colored thing
• We perceive shape before we grasp the shaped substance
• Yet intellection grasps the substance behind these sensible accidents
• This is why substance is named from standing under accidents—revealing the order of our knowledge

Important Definitions #

• Subsistence (subsistentia): Existing by itself, not in another as in a subject; derived from subsistere
• Hypostasis (ὑπόστασις): From ὑπό (hypo, under) + στάσις (stasis, standing); etymologically: individual substance; customarily used by Greeks for rational individuals specifically
• Nature (φύσις/phusis): Originally signified generation/birth; extended to intrinsic source of motion; finally, what a thing is (essence)
• Essence (ἐssentia/usia/οὐσία): What a thing is; signified by definition; the principles common to a species (not individual principles)
• Rational Nature (in context of person): Understood as intellectual nature; the capacity for understanding, not merely discursive reasoning
• Supposit/Suppositum (ὑποκείμενον): The subject underlying; the individual thing that subsists and stands under accidents
• Individual Substance (substantia particularis): A thing existing in itself, not in another; the second meaning of substance
• First Substance (πρώτη οὐσία/prima substantia): The individual thing (Socrates, Plato, this dog)
• Second Substance (δευτέρα οὐσία/secunda substantia): The universal (man, dog)—the species and genus

Examples & Illustrations #

The Division of Quadrilaterals #

• Aristotle begins Elements with five kinds: square, oblong, rhombus, rhomboid, trapezium
• As geometry develops, these are reorganized: the first four are all parallelograms
• Division follows the rule of two: parallelogram vs. non-parallelogram
• The four types result from crisscrossing two divisions:
  • Right-angled or not right-angled
  • Sides equal or not equal
• Results: Square (equal sides, right angles), oblong (unequal sides, right angles), rhombus (equal sides, non-right angles), rhomboid (unequal sides, non-right angles)
• This method shows how complex divisions can be reduced to systematic order

Fire and Water: Accidental Differences Substituting for Unknown Substantial Differences #

• Ancient definition: Fire is a simple body, hot and dry; water is a simple body, cold and wet
• Hot, dry, cold, wet are all in the category of quality (third species of sensible qualities)
• The substantial difference between fire and water is unknown or unnamed
• Therefore, accidental differences are used in place of substantial ones
• This reveals our weakness: we must use what we know (accidents) to signify what we don’t know (substantial differences)

The Separated Soul Cannot Be a Person #

• The soul alone, separated from body, is not a person
• Just as a hand severed from the body is not a hand (not in the full sense)
• A part cannot be an individual substance or hypostasis
• When we say “Peter is in heaven,” we use synecdoche (part for whole)
• The proper subject of personhood is the composite: soul united to body

The Example of Champion the Horse #

• An example of a beautiful horse the lecturer once encountered
• Illustrates the principle: the individual horse (this horse, Champion) is a particular substance
• Not universal like the concept “horse” but a particular thing that subsists

Questions Addressed #

Can a singular thing be defined? #

Answer: While the individual Socrates cannot be defined, the common notion of individuality can be. Aristotle defines first substance this way in the Categories. Person includes the notion of singularity in its definition, even though individual persons are not formally defined.

Why is “nature” more suitable than “essence” in the definition of person? #

Answer: Nature has a more determinate meaning; essence is taken from being, which is the most common term. Nature, derived from birth and generation, carries the idea of a source within a determined kind, making it more specific and appropriate for defining person than the overly broad term essence.

How are subsistence, nature, and hypostasis related to the common notion of substance? #

Answer: All three names for individual substance express the same reality from different perspectives:

• Subsistence: emphasizes that it exists by itself, not in another
• Nature: emphasizes that it is an individual of a determined kind
• Hypostasis: emphasizes that it stands under and supports accidents They are three ways of understanding a single reality: individual substance.

Why is the separated soul not a person? #

Answer: Because the soul is a part of human nature, not the whole. Only what is an individual substance can be a person. A separated soul, lacking its natural completion in the body, cannot be called an individual substance or hypostasis. It is a part, and parts are not persons, just as hands are not persons.

What is the relationship between these terms and equivocation? #

Answer: All these terms—substance, nature, hypostasis—are equivocal by reason, meaning they have multiple related meanings that are easily confused. Understanding the different senses prevents errors in philosophy and theology. Mixing these senses is the most common source of logical and metaphysical mistakes.