142. Knowledge, Reason, and the Eternal Reasons

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Lecture Notes

Main Topics #

• Common Reason and Truth: Heraclitus’s distinction between the private worlds of the sleeping and the common world of the waking; truth is one and common, not many and private
• Participation in Eternal Reasons: How human reason participates in divine knowledge through the natural light of the agent intellect, which is a partaking (participatio) of the uncreated eternal light
• Augustine’s Reconciliation of Plato and Aristotle: How Augustine appropriates what is true in Platonic forms while rejecting their separation from matter, replacing separated ideas with the eternal reasons existing in God’s mind
• The Source of Knowledge: Sense and Intellect: The proper object of human intellect is the essence or nature (quidditas) of sensible things; knowledge begins with sensation but transcends it through intellectual abstraction
• The Role of the Agent Intellect: The agent intellect makes potentially understandable things actually understandable, functioning as the “understandable light” that illuminates sensible images (phantasms)

Key Arguments #

The Truth as Common and One #

• When asleep, people have many private worlds and answers (e.g., 2+2 could equal 3, 5, or 6 in dreams)
• When awake, there is one common world with one true answer that all rational minds can access
• This reflects Heraclitus’s principle: “We should not act and speak like those asleep”
• The truth about what is common to all reason is the reflection of eternal reasons in every man’s reason

The Necessity of Something Common #

• In conversation between equals, progress requires finding something both parties agree upon to judge their disagreements
• In teaching, the teacher leads the student from things already known to things not yet known; thus both must share common ground
• Just as a city needs one common law (not different laws for different people), the life of the mind requires common principles accessible to all reason
• All particular laws are “fed by” (fed by) the natural law, which itself is a partaking of the divine law

Participation in Divine Light Through Natural Reason #

• The natural light of reason (the agent intellect) is a partaking (participatio) of the uncreated divine light
• What is naturally understood by the human mind is a partaking of the eternal reasons, not the eternal reasons themselves
• Only the blessed (the sancta and pura who see God) know all things in the eternal reasons as in an object
• In the present life, we know things in the eternal reasons as in a source or cause of knowledge, analogous to seeing things in the sun through the sun’s light
• This is why every man who comes into the world is “enlightened by this light” (John 1:9)—the natural light of reason, not faith, which not everyone has

Augustine’s Modification of Plato #

• Plato laid down that separated forms (ideas) subsist by themselves outside matter
• Augustine found this alien to the faith but recognized the truth in Plato’s insight about immaterial knowledge
• Augustine replaced Plato’s separated forms with the eternal reasons (rationes aeternae) existing in God’s divine mind
• According to these divine reasons, all creatures are formed; according to them also the human soul knows all things
• Augustine appropriates what is true in the pagan philosophers (as from “unjust possessors”) while rejecting what contradicts faith

Important Definitions #

• Participatio (Participation): The way creatures share in divine perfections; human reason participates in the eternal divine light and the eternal reasons through the agent intellect
• Agent Intellect (Intellectus Agens): The active power of the human soul that functions as the “understandable light,” making potentially understandable things (in phantasms) actually understandable through abstraction
• Understandable Light (Lux Intelligibilis): The agent intellect itself, compared by Aristotle to physical light; just as light makes potentially visible colors actually visible, the agent intellect makes potentially understandable sensibles actually understandable
• Eternal Reasons (Rationes Aeternae): The divine ideas existing in God’s mind according to which all creatures are formed and known; human knowledge is a partaking or likeness of these reasons
• Quidditas (What-it-is/Essence): The nature or essence of a thing; the proper object of human intellectual knowledge when abstracted from sensible particulars
• Phantasm (Phantasma): Mental image formed from sensory experience; the proper material upon which the agent intellect acts in the process of abstraction

Examples & Illustrations #

The Dog Example (Process of Abstraction) #

• A mother repeatedly points to dogs and says “see the dog”
• After the child has seen multiple dogs, he separates out what they have in common
• This separated universal is the beginning of rational knowledge
• The universal “dog” is not itself sensed but is understood from many sensible particulars

Mathematical Truth (2 + 2 = 4) #

• When asleep and dreaming, different people might answer 3, 5, or 6 to “what is 2+2?”
• When awake and using reason, all give the one true answer: 4
• This common knowledge is accessible to all rational minds and reflects participation in the eternal reasons
• It demonstrates that truth is one and common, not many and private

The City and Its Laws #

• A city requires one common law for all citizens to function (e.g., all drive on the same side of the street)
• Without this common law, there would be chaos
• Similarly, intellectual discourse requires common principles accessible to all reason
• All particular laws (speed limits, food safety, hunting regulations) are “fed by” one universal natural law to preserve human life and property
• This natural law is itself fed by the divine law, suggesting a hierarchy of laws ultimately grounded in divine wisdom

The Humility of Ancient Philosophers #

• Pythagoras, though called wise for his discoveries, rejected the title “wise” and said only God is wise; instead, he coined the term “philosopher” (lover of wisdom) to express humility
• Socrates, when told by the oracle that no one is wiser than he, maintained that his wisdom consists only in knowing that he knows nothing
• Plato rejected Protagoras’s claim that “man is the measure of all things” and instead affirmed that “God is the measure of all things”
• This humility recognizes the dependence of human reason on the eternal reasons in God

Notable Quotes #

“Listen not to me, but to reason” — Heraclitus, illustrating that truth appeals to what is common to all rational minds, not to private authority

“Those who speak with understanding must be strong in what is common to all, as much as the city is strong in its law, and even more so” — Heraclitus, on the necessity of common principles both in discourse and in social life

“For all the laws of the city are fed by one divine law, which is more than sufficient for all” — Heraclitus, indicating the hierarchy of laws ultimately grounded in the divine

“The light of your face is sealed upon us, Lord” — Psalm 4:6-7, cited by Thomas to express how divine light illuminates human reason, making truth manifest to all

“This was the light that enlightens every man who comes into this world” — John 1:9, interpreted as referring to the natural light of reason as a participation in divine light, which all humans possess

“As a child is to a man, so is man to God” — Heraclitus, expressing the humility of recognizing human reason’s dependence on divine wisdom

“God alone is wise” — Pythagoras, the foundational humility of philosophy recognizing wisdom belongs to God alone

Questions Addressed #

How Do We Know What Is Common? #

• Question: If Heraclitus tells us to “listen not to me, but to reason,” what reason is he referring to if reason differs in each person?
• Answer: He refers to what is common to all reason—those truths naturally understood by every rational mind (e.g., “a whole is greater than one of its parts”). This common understanding is a partaking of the eternal reasons.

How Does the Soul Know All Things in the Eternal Reasons? #

• Question: Does the human soul, in this present life, see the eternal reasons themselves as objects of knowledge?
• Answer: No. Only the blessed who see God directly know all things in the eternal reasons as in an object. In this life, we know things in the eternal reasons as in a source or cause of knowledge—through the participation of the agent intellect in the divine light.

What Is the Relationship Between Natural Reason and Divine Light? #

• Question: Is the natural light of reason a partaking of divine light, or is it merely something different from faith?
• Answer: Yes, the natural light of reason is a partaking of the eternal divine light. Just as physical light makes colors actually visible, the agent intellect (the understandable light) makes sensibles actually understandable. Both are participations in the uncreated light in which the eternal reasons are contained.

Why Must We Appeal to Something Common in Discourse? #

• Question: How can two people in disagreement ever make progress in understanding?
• Answer: They must find something common to both—some principle or truth that both accept—and use it to judge where they disagree. Without this common ground, dialogue becomes mere contradiction. This necessity reflects the deeper truth that all rational minds participate in eternal reasons.