18. The Five Predicables: Definitions and Distinctions

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Lecture Notes

Main Topics #

The Five Predicables and Their Definitions #

Genus: A name said with one meaning (univocally) of many things other in kind, signifying what it is in a general way. Has five parts in its definition: (1) a name, (2) said with one meaning, (3) of many things, (4) other in kind, (5) signifying what it is.

Difference: A name said with one meaning of many things other in kind, signifying how they are what they are (not what they are). Shares the first four parts of genus’s definition but differs in the fifth part.

Lowest Species (ἔσχατον εἶδος): A name said with one meaning of many things, other only individually (not other in kind), signifying what it is. The strictest sense of species—distinguished from genus by a single difference (individuals rather than kinds).

Species (in broader sense): A particular kind of thing under a genus; any name that plays the role of specifying a kind of thing in relation to what is above it (genus) and below it (individuals or lower species).

Property and Accident: Mentioned but not detailed in this lecture.

The Problem of Most Universal Names #

Berquist establishes that not every genus has a genus above it:

• If every genus required a genus above it, infinite regress would make knowledge impossible
• One would need infinite definitions before any definition could be formed
• Therefore, there must be most universal names—being, something, thing—that cannot be further universalized
• These cannot be defined further: “Can there be something that is not a being?”

Univocal vs. Equivocal Predication #

The crucial question: Are the most universal names said univocally (with one meaning) or equivocally (with multiple meanings)?

• If univocal: There would be one highest genus of everything
• If equivocal by reason: There would be multiple highest genera
• Aristotle showed these names are not said univocally with the same meaning, therefore there is not one highest genus but multiple highest genera
• This leads to Aristotle’s doctrine of the categories

The Structure of Definitions #

Definitions typically contain one genus and multiple differences:

• No single difference is convertible with the thing being defined—only the combination of differences achieves this
• Example: Square = equilateral AND right-angled quadrilateral
  • Equilateral alone does not define square (rhombus is also equilateral)
  • Right-angled alone does not define square (oblong is also right-angled)
  • Only both together specify square uniquely
• This reflects our knowledge of things outwardly before inwardly
• Definition moves from confused to distinct knowledge

Relations Between the Predicables #

Genus and Difference:

• One difference: genus signifies what it is; difference signifies how it is what it is
• Both share: said with one meaning, of many things other in kind

Genus and Lowest Species:

• One difference: genus is said of many things other in kind; lowest species of many things other only individually
• Both share: signify what it is

Difference and Lowest Species:

• Two differences: (1) difference signifies how vs. species signifies what; (2) difference is said of things other in kind vs. species only individually
• Both share: said with one meaning, of many things

Relative Distinctions: The same name can be both genus and species depending on comparison:

• Quadrilateral is a species when compared to rectilineal plane figures
• Quadrilateral is a genus when compared to square, rhombus, oblong

Key Arguments #

Why Not Every Genus Has a Genus Above It #

First argument (from knowledge):

• If every genus had a genus above it, you would need to know infinitely many things before knowing anything
• One must know the genus quadrilateral before knowing square, but cannot know square if there’s always a more universal genus required
• This creates infinite regress: “In which case, you should know nothing”
• Therefore, there must be most universal names at which one stops

Second argument (from most universal words):

• There are demonstrably most universal names: being, something, thing
• Nothing can be more universal than these
• If every genus required a genus above it, these most universal names would not exist
• But they do exist, so not every genus has a genus above it

Why No Single Difference Is Convertible With a Species #

Thomas Aquinas raises a question in his Commentary on the Posterior Analytics: If genus comes from matter and difference from form, and unity requires one form, why shouldn’t there be a difference convertible with the thing?

Answer: We know things outwardly through sensation before knowing them inwardly. Therefore:

• We tend to guess at interior nature from exterior appearances
• No part of any definition is fully convertible with the thing defined
• Each part of the definition represents confused knowledge of the species
• Only the combination of all parts brings the mind from confused to distinct knowledge
• This reflects that definition is a process moving from general to specific understanding

Why There Cannot Be One Highest Genus #

• The most universal names (being, something, thing) are not said univocally with one and the same meaning
• They are said equivocally by reason (ἀμφιβολία κατὰ λόγον)
• Therefore, there cannot be one highest genus encompassing all things
• This necessitates multiple highest genera, leading to the doctrine of categories

Important Definitions #

Said with one meaning (ἐπὶ τοῦ αὐτοῦ λόγου / univocally): Predicated of many things with the same meaning and definition. The second part of every predicable’s definition.

Other in kind (ἕτερα τῷ εἴδει): Things differing not merely as individuals but as different kinds or species. Distinguishes genus and difference from lowest species.

Signifying what it is (τὸ τί ἐστιν): Indicating the essence or nature of a thing. The fifth part of genus and lowest species definitions.

Signifying how it is what it is (τὸ ποῖόν τι ἐστιν): Indicating the mode or manner of the thing’s being, not its essence. The fifth part of difference’s definition.

Lowest Species (ἔσχατον εἶδος): A species that has nothing below it; said of many individuals only, not other in kind.

Highest Genus (γένος ἀνώτατον): A genus that is not a species of anything above it.

Convertible (κατηγορεῖσθαι ἀντιστρόφως): Two things are convertible when every A is B and every B is A. A definition should be convertible with the thing defined.

Equivocal by reason (ἀμφιβολία κατὰ λόγον): Said with different meanings but with some connection or reason between the meanings (unlike equivocal by chance, where there is no connection).

Examples & Illustrations #

Geometric Examples #

Quadrilateral and Its Species:

• Quadrilateral (genus) → square, oblong, rhombus, rhomboid, trapezium (species)
• Equilateral (difference): separates square and rhombus from oblong and rhomboid
• Right-angled (difference): separates square and oblong from rhombus and rhomboid
• Only the combination of both differences specifies square uniquely
• No genus exists that encompasses the oblong when the ratio of longer to shorter side is not specified

Triangle and Its Species:

• Triangle (genus) → equilateral, isosceles, scalene (species)
• Equilateral triangle has no single name; must be expressed as a speech
• Despite lacking a name, it plays the same role that square plays for quadrilateral—it is a lowest species

Arithmetic Examples #

• Even and odd numbers: These are not lowest species; 7 (odd) and 8 (even) are lowest species
• Prime and composite: Both are genera (can be further divided)

Natural Philosophy Examples #

• Man appears to be a lowest species (animal with reason—where there is no species of reason)
• Dog: Different kinds of dogs exist, suggesting dog may not be lowest species
• The question of whether species differences are real or merely how we divide things

Poetic Examples #

From Berquist’s study of comedy:

• Good-natured comedy and satire are different forms of comedy
• Good-natured comedy expels laughter naturally; satire makes one laugh through shock (like Swift’s works)
• Shakespeare wrote three good-natured comedies but two satires
• Satire can be more impersive and shocking than good-natured comedy

Speech vs. Name #

When a lowest species lacks a single name, one uses a speech instead:

• “Equilateral triangle” is a speech (two names), not a single name
• “Rational animal” used to define man
• In drama, “tragicomedy” or “romance” are used for kinds of drama between tragedy and comedy
• The same logical function is served, even without a single name

Notable Quotes #

“Of many, what? Individuals, right? Okay? Many that differ only as individuals, not differing in kind, signify what it is.” — On the definition of lowest species

“If every genus had a genus above it, how many genus would you have to know to know anything? Yeah. In which case, you should know what? Nothing.” — On the impossibility of infinite regress in predication

“There are most universal words. Like take the word something or the word thing or the word being, right? Can there be something that is not a being?” — On the existence of most universal names

“Only a combination of the differences brings you from a confused knowledge to a, what, distinct knowledge, right?” — On how definitions move from confusion to clarity

“Nature loves to hide.” — Heraclitus, cited on why we know things outwardly before inwardly

“The combination has to fit just that one thing, right?” — On how multiple differences must combine to define a unique species

Questions Addressed #

Can the same name be both genus and species? #

Answer: Yes, but only in a relative sense. Quadrilateral is a species compared to rectilineal plane figures, but a genus compared to square. This is not an absolute but a relative distinction.

Does every genus have a genus above it? #

Answer: No. If it did, infinite regress would make knowledge impossible. There must be most universal names (being, something, thing) that cannot be further universalized. Both the need for knowledge to begin somewhere and the existence of demonstrably most universal words prove this.

Are the most universal names said univocally or equivocally? #

Answer: According to Aristotle, they are said equivocally by reason, not univocally with one meaning. This means there is not one highest genus but multiple highest genera, leading to the doctrine of categories.

Why do definitions require multiple differences rather than one? #

Answer: Because we know things outwardly before inwardly. No single difference is peculiar to a species; each is common to multiple species. Only the combination brings distinct knowledge. This reflects our natural progress from confused to distinct understanding.