2. Logic, Predication, and the Three Acts of Reason

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Lecture Notes

Main Topics #

Logic Proceeds by Way of Predication #

Thomas Aquinas teaches that while natural philosophy proceeds by way of motion (per modum motis), logic proceeds by way of predication (per modum praedicationis). This means:

• Everything in logic relates to how something is “said of” something else
• The fundamental operation is the predication—the way a name or term is predicated of many things
• The first books of Albert the Great on logic are called the Predicabilia and Predicamenta, both derived from the notion of predication

The Three Acts of Reason (Thomas Aquinas) #

Thomas divides logic into three parts corresponding to three acts of reason:

1. First Act: Understanding What Something Is (Simple Apprehension)

   • Grasping the essence or nature of a thing
   • Examples: understanding what a square, circle, or dog is
   • Aristotle calls this intelligere (understanding)
   • Corresponds to Aristotle’s Categories

2. Second Act: Understanding True or False (Judgment)

   • Putting together or separating concepts understood in the first act
   • Composition-division: composing in affirmative statements, dividing in negative statements
   • Example: “A square is a quadrilateral” (true) vs. “A square is a circle” (false)
   • Corresponds to Aristotle’s Peri Hermeneias (De Interpretatione)

3. Third Act: Reasoning (Discursive Thought)

   • Putting together statements to reach new conclusions
   • Moving from known to unknown through argument and syllogism
   • Corresponds to Aristotle’s Analytics and other works on reasoning

Alternative Division: Albert the Great’s Twofold Approach #

Albert divides logic into two parts:

• Art of Defining: Coming to know the simple unknown (what is X?)
• Art of Reasoning: Coming to know the complex unknown (is X true?) and reasoning itself

Albert combines Thomas’s second and third acts because both involve discourse directed toward knowing. This division emphasizes that logic is not an end in itself but a means to knowledge.

The Natural Road in Logic #

Despite logic’s concern with immaterial relations, it cannot entirely avoid the natural road—the progression from sense knowledge to intellectual knowledge:

• Called “natural” because man is a rational animal; sense perception (animal nature) develops before reason
• Logic begins with names said of things, which are sensible (spoken sounds)
• The order of naming follows the order of knowing: word (sensible) → thought (intelligible) → reason (faculty)

Key Arguments #

Why Logic Studies the Universal #

Following Shakespeare’s definition of reason as “ability for large discourse”:

• Large means covering a large area
• Logic’s primary concern is the universal—terms said of many things
• Example: “man” is said of every human being (past, present, future); no end to how many things it’s said of
• Universal discourse covers a larger area than particular discourse (biography, history)
• Poets present “the universal singularized”—a character type (e.g., a jealous man) embodied in particular form

Univocal, Equivocal, and Equivocal by Reason #

Names said of many things can be classified:

• Univocal: Same meaning in all instances (e.g., “animal” said of dog and cat; “quadrilateral” said of square, rectangle, rhombus)
• Equivocal: Different meanings in different instances (e.g., “bank”—financial institution vs. riverbank)
• Equivocal by Reason: A middle ground where meanings are related by some connection or order

Equivocal can be further divided:

• By Chance: No connection between the different meanings (e.g., three men named Richard who are unrelated)
• By Reason: A genuine connection or order between meanings (e.g., logos: word → thought → reason, where each meaning is connected through signification and causation)

Important Definitions #

Name vs. Speech #

Both are vocal sounds signifying by custom/human agreement (not by nature):

• Name (nomen): Vocal sound signifying by custom, having no parts that signify by themselves

  • Example: “Duane”—syllables don’t have independent meanings
  • Even compound names like “Johnson” (son of John) or “Bergquist” (mountain branch) function as single units
  • Etymology (historical origin) ≠ Meaning (current function)

• Speech (sermo): Vocal sound signifying by custom, having parts that signify by themselves

  • Example: “white man”—both “white” and “man” have independent meanings
  • Includes definitions, statements, and arguments

Three Kinds of Speech Perfecting the Three Acts #

1. Definition: Speech making known/bringing out what something is

   • Composed of genus and difference
   • Example: “Square is an equilateral and right-angled quadrilateral”

2. Statement (propositio or better, enuntiatio): Speech signifying true or false

   • Truth is where true/false is found (in statements, not in things themselves)
   • Contradictory statements: one true, one false

3. Argument/Syllogism: Speech putting together statements to reach conclusion

   • Syllogism: argument where conclusion follows necessarily from premises
   • Broader category is “argument” (speech using statements to reach conclusion)

Predication (Praedicatio) #

In the strict sense, a syllogism is based on the “set of all” and the “set of none”—this is what predication means: the way something is said of something else.

Examples & Illustrations #

Understanding the Three Acts in Practice #

First Act:

• Understanding what a square is
• Understanding what a circle is
• Understanding what an odd number or even number is
• Understanding the difference between a dog and a cat

Second Act:

• “A square is a quadrilateral” (TRUE—saying what is, is)
• “A square is not a circle” (TRUE—saying what is not, is not)
• “A square is a circle” (FALSE—saying what is not, is)
• “You are sitting now” (TRUE if actually sitting; saying what is, is)

Third Act:

• Putting together premises to draw a conclusion through reasoning
• Syllogisms that demonstrate (make you know the cause)

Equivocal by Chance #

• Three men named Richard: Berquist’s brother, a student in his house, a manager at a package store
• No connection between them; merely happened to share the same name
• Two apostles named Judas (one good, one infamous)

Equivocal by Reason #

• Logos: Word → Thought → Reason
  • Connected by natural progression: word is sensible, thought is signified by word, reason is faculty producing thoughts
  • Each meaning relates to the others through signification and causation

Etymology vs. Meaning #

• Johnson: Etymology = “son of John,” but person named Johnson may not be John’s son
• Bergquist: Etymology = “mountain branch” (Berg + quist), but family is not mountain branches
• Etymology traces historical origin; meaning is how a word functions in current use

Notable Quotes #

“Logic proceeds by way of predication” - St. Thomas Aquinas (contrasted with natural philosophy proceeding by way of motion)

“Reason is the ability for large discourse, looking before and after” - Shakespeare (cited by Berquist to explain why logic concerns the universal)

“Nature likes to hide” - Heraclitus (explaining why definitions must bring out or make manifest what things are)

“All knowledge begins and ends in the senses” - Aristotle and Albert Einstein (showing agreement across millennia on the natural road)

Questions Addressed #

Q: How does logic differ from natural philosophy? A: Natural philosophy proceeds by way of motion (what things do); logic proceeds by way of predication (how things are said of other things). Logic begins with the sensible (spoken words/names) but rises to intelligible relations among universal concepts.

Q: Why does Thomas divide logic into three parts instead of two? A: Thomas follows the three distinct acts of reason themselves. Albert’s twofold division (defining vs. reasoning) is also valid but emphasizes logic’s goal: coming to know the unknown. Both approaches have merit depending on one’s emphasis.

Q: What is the difference between equivocal by chance and equivocal by reason? A: By chance: no connection between the different meanings (e.g., unrelated people with the same name). By reason: the meanings are genuinely related by some order or connection (e.g., logos: word signifies thought, thought is produced by reason).

Q: Where is truth or falsity found? A: In statements (the second act), not in things themselves or in the ocean or air. Truth is found in statements that correctly correspond to reality; falsity in those that do not.

Q: Can an equivocal word be used univocally? A: Yes. An equivocal word (having multiple meanings) can be used univocally if, in a particular instance, only one of its meanings is intended and applied consistently.

Key Distinctions #

Predication and Categories #

Aristotle’s Categories is not strictly about definition but about the ten supreme ways things are predicated (the “ten accusations” or predications):

• The word categories derives from Greek katēgorein (to accuse, to predicate)
• Berquist notes the striking translation: “Ten Supreme Accusations” (modes of predication)
• Both Predicabilia and Predicamenta concern predication but from different angles

The Structure of Logic’s Study #

Following the natural road from sensible to intelligible:

1. Names (sensible vocal sounds)
2. Speech composed of names
3. How names are predicated and related to things and to each other