14. God's Existence: The Five Ways of Thomas Aquinas

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Lecture Notes

Main Topics #

Overview of the Five Ways #

• Thomas provides five demonstrations for God’s existence, not proofs
• Each argument begins from observable features of creation and proceeds to God as first cause
• The arguments vary in their development between Summa Theologiae and Summa Contra Gentiles
• All arguments follow a similar logical structure: observation → causal principle → conclusion to God
• These are demonstrations quia (that it is so), not propter quid (why it is so), because we cannot know God’s essence directly

Why God’s Existence Requires Demonstration #

• God’s existence is per se notum in itself (self-evident in itself) but not per se notum to us
• We do not know what God is by nature, only through effects
• Demonstration is valid even when effects are not perfectly proportioned to their cause
• The proper response to those who claim it is obvious or impossible: it is knowable through reason but requires careful argument

The Order and Manifestness of the Arguments #

• The first way (from motion) is called “more manifest” (manifestior) because motion most readily catches the senses
• Following Shakespeare’s Troilus and Cressida: “Things in motion sooner catch the eye than what not stirs”
• Our knowledge begins with sensation, and motion is most sensible to us
• The first argument has special priority pedagogically, not necessarily metaphysically

Key Arguments #

First Way: From Motion #

Major Premises:

1. Whatever is moved is moved by another (omne quod movetur ab alio movetur)
2. There cannot be an infinite regress of moved movers; there must be an unmoved mover

Philosophical Foundation:

Definition of Motion: The act of what is in potency insofar as it is in potency (actus entis in potentia, inquantum in potentia)

• Motion is not the full actualization (e.g., being completely in the room)
• Motion is not accidental states (e.g., standing in a doorway)
• Coming into the room = the imperfect act of the ability to be in the room
• Becoming hot = the imperfect act of the ability to be hot
• Motion is essentially ordered toward further actualization

The Principle of Actuality:

• Nothing is moved except according as it is in potency to that which it is moved toward
• The thing moving must be in act to move something from potency to act
• “To move is nothing other than to lead something from potency into act”
• Example: Fire (actually hot) makes wood (potentially hot) actually hot
• A thing cannot be simultaneously in act and potency in the same respect

The Impossibility of Self-Motion:

• Nothing can move itself (impossibile est idem et secundum idem movere et moveri)
• Therefore, everything that is moved is moved by another

The Problem of Infinite Regress:

• A moved mover is by definition a middle—it has something before it and something after it
• Whether you have one or many moved movers linked together, they constitute one grand moved mover
• The number of moved movers (one or many, limited or unlimited) does not solve the problem
• With nothing before this grand moved mover, nothing would move at all
• Therefore, there must be an unmoved mover

Alternative Approach via “Through Itself” Principle:

• An axiom: Before “through another” there must be “through itself”
• If everything is a mover through another, how can there be any movers at all?
• A mover through itself cannot be a moved mover (by definition)
• Therefore, there must be an unmoved mover
• This unmoved mover is what all understand to be God

Second Way: From Efficient Causality #

Major Premises:

1. There is an order of efficient causes (makers) in sensible things
2. Nothing can be the maker of itself
3. An infinite regress of efficient causes is impossible

Key Principles:

The Impossibility of Self-Causation:

• To be the maker of oneself would require being before oneself—a contradiction
• Uses the axiom of before and after: nothing is before or after itself
• Even popular ideas like “self-made man” are strictly false

The Structure of Ordered Causes:

• In ordered efficient causes: the first is cause of the middle, and the middle is cause of the last
• This holds whether there are many causes or one, limited or unlimited
• The distinction is always between maker (causa) and made (effectus)

Removal of Causes:

• “If the cause is removed, the effect is removed”
• If there is no first efficient cause, there would be no last effect
• If there is no first cause, there would be no middle causes either
• Therefore, there must be a first efficient cause, which all call God

Comparison to Aristotle’s Four Causes:

• Aristotle discusses efficient cause as the “mover” and extends to “maker”
• The maker has more sense of being a cause of the form and existence of the thing
• Motion (change of place) is more immediately sensible than being/form
• The argument proceeds from what catches our senses to more abstract causality

Third Way: From Possibility and Necessity #

Key Distinction:

• “Possible” (possibile) here means “able to be and not be” (contingent beings)
• This differs from logical possibility (compatibility of predicates)
• Contingent beings are those that come to be and pass away (generabilia et corruptibilia)

The Argument Structure:

1. If all things are contingent (able to be and not be), then at some time nothing existed
2. What is not cannot begin to be except through something that is
3. If nothing existed at some time, nothing could begin to exist now
4. But things do exist now—this is clearly false (manifestum)
5. Therefore, not all beings are contingent; there must be something necessary

Analysis of Necessary Being:

• Every necessary being either has a cause of its necessity or does not
• An infinite series of necessary beings each caused by another is impossible
• Therefore, there must be something necessary through itself (per se necessarium)
• What exists through itself must be existence itself (esse)
• This is God

Location in Summa Contra Gentiles:

• This argument is anticipated in the Summa Contra Gentiles but in different form
• The backing for the premises differs between the two Summas
• The principle of act before potency appears in Aristotle’s Book IX of the Metaphysics

Further Ways (Fourth and Fifth) #

• The lecture does not complete detailed coverage of ways four and five
• Berquist indicates these are somewhat similar to treatments in Summa Contra Gentiles
• The fourth way proceeds from grades of perfection; the fifth from governance of things

Important Definitions #

Motion (Motus) #

• Definition: The act of what is in potency insofar as it is in potency (actus entis in potentia, inquantum in potentia)
• Scope: Includes not only local motion but also alteration, growth, and other changes
• Distinction from full act: A person coming into a room is in motion but not yet fully in the room
• Distinction from accidental states: A person standing in a doorway is partially in the room but not in motion toward being further in it
• Essential ordering: Motion is essentially ordered to further actualization—so long as motion continues, further actualization occurs

Potency (Potentia) #

• General: The ability or capacity to be or become something
• Passive potency: The capacity to be acted upon; what is moved is in passive potency to what moves it
• Active potency: The capacity to act upon something
• Self-limitation: What is in potency cannot actualize itself; it requires what is already in act

Act (Actus) #

• General: The realization or actualization of potency
• Causal principle: What is in act can move what is in potency; the mover must be in act
• Priority: Act is prior to potency simply speaking, though in a particular thing potency comes first
• Exemplar: Fire is hot in act and makes wood hot in act (from potential hotness)

Contingent Being (Ens Contingens) #

• Definition: Something that is able to be and not be (quod potest esse et non esse)
• Characteristics: Characterized by coming to be and passing away (generabilia et corruptibilia)
• Dependency: Depends on something else for its existence; cannot explain its own existence

Necessary Being (Ens Necessarium) #

• Definition: Something that cannot not be
• Dual possibility: Either has a cause of its necessity or is necessary through itself
• God’s nature: God alone is necessary through himself (per se necessarium) and is existence itself

Efficient Cause (Causa Efficiens) / Maker (Faciens) #

• Definition: The agent or cause that brings something into being
• Distinguished from: Material cause (matter), formal cause (form), final cause (end)
• In Aristotle: First called “mover” (kinoun), then extended to “maker”
• Relationship: Maker and made are always distinct; nothing makes itself

Through Itself vs. Through Another (Per Se vs. Per Aliud) #

• Per se (through itself): A thing has a property or causality intrinsically, by its own nature
• Per aliud (through another): A thing has a property or causality by something else
• Axiom: Before the through another, there must be the through itself
• Example: Coffee is sweet through sugar (per aliud); something must be sweet through itself

Before and After (Prius et Posterius) #

• Multiple senses:
  1. Before in time (tempore)
  2. Before in being (essentia): this could be without that, but not vice versa
  3. Before in the discourse of reason (ratione) / in knowing
  4. Before in goodness or excellence (bonitate)
  5. Before as cause to effect (sicut causa ad effectum)
• Axiom: Nothing is before or after itself
• Application: If something is maker of itself, it would be before itself—impossible

Examples & Illustrations #

Motion Examples #

Coming into the Room:

• Coming into the room ≠ the act of the ability to come into the room (circular)
• Coming into the room = the imperfect/incomplete act of the ability to be in the room
• Standing in the doorway: one foot in, one foot out (accidental; not ordered to being further in)
• While in motion toward being fully in the room, you will be more in the room than before

Heating Water:

• Becoming hot = the imperfect act of the ability to be hot
• Being warm ≠ being hot (different states)
• Heating milk: one can be warm without ever becoming warmer or approaching hotness (accidental)
• So long as becoming hot continues, the water will be hotter than before

The Train Example:

• The caboose: moved, doesn’t move anything
• A railroad car: pulled puller (moved mover)—pulls the caboose while being pulled itself
• Two cars together: one grand pulled puller
• Infinite cars: still one grand pulled puller with nothing before it
• With nothing pulling the first car, nothing moves
• Therefore, there must be a mover that is not itself moved

Fire and Wood:

• Fire is hot in act
• Wood is hot in potency (able to be hot)
• Fire makes the wood actually hot
• The mover (fire) must be in act; the moved (wood) must be in potency

Causality Examples #

Sugar and Coffee:

• Both are sweet, but coffee is sweet through sugar
• What would make something sweet if nothing is sweet through itself?
• First things known must be known through sensible objects, not through other words

Learning Words:

• A child learns “cookie” by associating the sound with the object
• If all words had to be known through other words, nothing would ever be known
• First words are learned per se (through the object), not per aliud (through other words)
• Berquist’s tape recording of teaching his son Paul the word “cookie”

Self-Made Man:

• Common expression: “self-made man”
• Strictly false: contradictory to be cause of oneself
• Even if one’s father is called “self-made,” this is incomplete analysis
• Sartre (even from existentialist perspective) sees this as “useless passion”

Axioms and Principles #

The Axiom of Before and After:

• Nothing is before or after itself
• If something were before itself, it could be without itself (contradiction)
• Used to show: self-causation is impossible, nothing moves itself

The Axiom of Whole and Part:

• A whole is greater than any of its parts
• Observable once you understand what a whole and part are

The Principle of Fewness:

• “Nature is pleased with simplicity and affects not the pomp of superfluous causes” (Newton)
• Fewer causes are better if they are sufficient
• Do not multiply causes beyond necessity
• This principle can support or challenge various arguments depending on what sufficiently explains the phenomena

Notable Quotes #

“Things in motion sooner catch the eye than what not stirs.” — Shakespeare, Troilus and Cressida (cited to explain why the first way is “more manifest”)

“Nihil dhat quod non habat.” — Scholastic axiom: “Nothing gives what it doesn’t have” (Berquist’s seminary professor would emphasize this to show why students couldn’t answer without knowledge)

“Nature is pleased with simplicity, and affects not the pomp of superfluous causes.” — Newton, Principia (the principle of fewness in causes)

“I am who am.” — Exodus 3:14 (cited as the definitive text against the second objection that God’s existence cannot be demonstrated)

“For to move is nothing other than to lead something from potency into act.” — Thomas Aquinas (central principle of the motion argument)

“Everything that is moved, necessarily is moved by another.” — Thomas Aquinas (first major premise of the first way)

“If the cause is removed, the effect is removed.” — Principle cited in the second way (causa sublata, sublatum effectus)

Questions Addressed #

Why is God’s Existence Not Self-Evident to Us? #

• God’s existence is self-evident in itself (per se notum in se)
• But we do not know what God is by nature
• Therefore, it is not self-evident to us (per se notum quoad nos)
• We must proceed from effects we can know to the cause we cannot directly know

Why Compare Summa Theologiae with Summa Contra Gentiles? #

• The arguments are not identical in the two works
• Motion arguments are more developed in Summa Contra Gentiles (two arguments vs. one)
• The third way appears differently in each work
• Later works sometimes expand earlier arguments, sometimes condense them
• One cannot judge chronology by length (e.g., Mark’s Gospel is short but not necessarily first)
• Different works have different purposes and audiences

Why Must There Be an Unmoved Mover? #

• A moved mover is by definition a middle with something before and after
• Whether one or many, linked moved movers constitute one grand moved mover
• With nothing before this grand moved mover, nothing moves
• Since motion exists, there must be something that is not itself moved

How Do We Know Not Everything is Through Another? #

• If everything were a mover through another, there would be no movers at all
• The same applies to knowing: if everything were known through other things, nothing would be known
• Therefore, there must be something through itself (per se)

Why Can’t an Infinite Series of Efficient Causes Work? #

• In ordered causes: the first causes the middle, the middle causes the last
• This holds whether limited or unlimited in number
• If there is no first cause, there is no last effect
• But effects exist, so there must be a first cause

What About Modern Misunderstandings? #

• Even modern Thomists often misunderstand the major and minor premises
• The five ways require genuine understanding, not superficial familiarity
• Teaching these to freshmen without true understanding produces naive applications
• Berquist cautions against intellectual pride; even professionals often misinterpret these arguments

Pedagogical Warnings #

On Studying These Arguments #

• Do not be overly ambitious; focus on genuine understanding
• Must fully understand these arguments, meeting them several times
• Even professional philosophers and theologians often misunderstand them
• Each argument depends on understanding whole sections of Aristotle’s physics and metaphysics
• The Summa Contra Gentiles provides much more developed backing for the premises

On False Confidence #

• Catholic colleges teaching the five ways to freshmen as if obviously true and quickly learnable
• Students claiming these will “convert the world” without real understanding
• The premises are not obvious and require serious metaphysical background
• Many intelligent people have rejected these arguments, not from stupidity but from misunderstanding them

On Chronological Judgments #

• Cannot judge which work comes first by which is longer or shorter
• Both expansion and condensation occur as thinkers develop their thought
• Must examine each work on its own terms and in its context
• Comparison helps understanding but does not establish chronological priority

Textual Connections #

Aristotle’s Physics #

• Book III: Definition of motion
• Book VI: Middle terms for some premises of motion argument
• Book VIII: Development of unmoved mover argument for motion; arguments for Aristotle’s first principles

Aristotle’s Metaphysics #

• Book II: Principle that things most true are most being
• Book V: Multiple meanings of cause and before/after
• Book IX: Act before potency (simply speaking)

Thomas Aquinas’s Works #

• Summa Contra Gentiles: More developed arguments, particularly for motion (two arguments)
• Commentary on the Sentences: Earlier treatment of existence of God
• Commentary on Psalm 21: David as figure of Christ (illustrating literal sense in Scripture)
• Leona edition commentary on Job: Book of Job ordered to defense of faith against evil objection

Scripture #

• Exodus 3:14 (“I am who am”): Divine self-revelation
• Psalm 21 (51): Penitential psalm with Christ as subject in Thomas’s reading
• Psalm 24: Via and semitah (way and path) as commands and counsels
• Matthew and Mark: Christ’s words on the cross from Psalm 21
• Romans 1:20: “Invisible things of God…understood from things made”

Conceptual Clarifications #

Motion vs. Rest #

• Rest is not the opposite of motion but the cessation of motion
• Rest occurs when something ceases to be ordered to further actualization
• Example: Man standing in doorway at rest (not progressing further into room)

Potency and Actuality #

• Potency is not mere logical possibility but real capacity in a thing
• Actuality is not just a state but a dynamic realization
• The mover actualizes what is potential in the moved

Cause and Dependence #

• Efficient cause: the agent producing the effect
• Causal dependence: the effect requires the cause for its existence or operation
• An infinite series of dependent causes cannot explain anything

Through Itself (Per Se) vs. Through Another (Per Aliud) #

• This distinction underlies several of the five ways
• Applied to motion, causality, necessity, and knowledge
• The principle: the per aliud must ultimately rest on the per se