The Legacy of Ancient Greek
Philosophy
Prof. Rob Koons
Edward Feser, The Last Superstition: A Refutation of the New
Atheism, Chapter 2
Leadership for America 2013
Socrates vs. The Sophists
Socrates (469-399 B.C)
Opposed the Sophists (the
Wise Men), who tended
toward skepticism and
relativism (“Man is the
measure of all things”).
Socrates used rational
dialogue in order to seek the
essences or “definitions” of
things, especially ethical ones,
like Justice, Courage or
Friendship.
Plato’s Theory of “Forms”
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A “Form” is the kind of essence that Socrates
sought: the Form of Justice, the Good, Humanity,
etc.
Forms are not physical objects, nor something
private, subjective or merely mental. A “third
realm”.
Examples: mathematical objects, like the triangle.
For Plato, material objects (including us) are faint,
imperfect copies of some perfect Form.
This fact has normative implications: something is
a better F the more perfectly it copies the form of
the F. Better triangles, better men.
In modern philosophy, Plato’s Forms are
classified as “abstract objects”. They are typically
called “universals”.
Why believe in Forms or Universals?
1. The “One over Many” argument. All triangles share something in common,
even if this common element were never recognized or thought of. It could
exist even if all “instances” of it (physical triangles) were destroyed.
2. Such abstract objects are studied in mathematics, which studies real things
but not physical things.
3. The nature of propositions (truths and possible truths). These would exist
and could be true even if they were no material objects and no minds.
4. The argument from science. All sciences investigate universal laws, which
are not about particular things but about their common natures.
5. Language necessarily involve universals. A word or word-type (like “red”) is
itself a universal, instantiated by many physical and psychological tokens.
There are sentences in English that have never been and never will be
spoken, and yet which have definite meanings.
6. The objectivity of concepts and the possibility of storing and communicating
knowledge. We cannot literally share our ideas nor store them – all we can
remember or communicate are universal contents.
The Philosophy of Aristotle
Aristotle (388-322 BC) was
Plato’s student.
Influenced all later Christian
philosophers, including
Augustine and Thomas
Aquinas.
Wrote on many subjects:
biology, chemistry, astronomy.
Best-known: Categories,
Metaphysics.
“Moderate” Realism about Universals
• Aristotle agreed with Plato that universals (forms) must
exist to make science and thought possible.
• However, he rejected the idea that material objects were
mere “copies” of separately existing Forms.
• Instead, he insisted that the Forms existed “in” particular
objects. A universal (like humanity or justice) exists only
insofar as there actual humans or just people.
Species and Genus
Genus
Differentia 1
Species 1
Differentia 2
Species 2
The Ten Categories
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Substance
Quantity
Quality
Relation
Place
Time
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Position (attitude)
State (having)
Action
Affection (having
been acted on)
Primary vs. Secondary Substance
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Reverses Plato’s priorities: it is the
(changeable) particular substance that
is most real (most fully substantial).
Secondary substances are substantial
only in a “qualified way”: by referring
to classes (natural kinds) of
substances.
Species are more fully substantial than
genera, because closer to individuals.
Substance vs. Accidents
• Besides substance, the other categories
(quantity, quality, relation, etc.) are
categories of ‘accidents’.
• Individual accidents are “present in”
substances, in such a way that there is a
one-way dependency of the accident on its
substantial bearer.
• Aristotle: “Humanity is not present in the
individual man.” Why not? Is there such a
thing as Socrates’ humanity?
Four-Fold Division
Not present
in a subject
Not
predicated of
a subject
Particular
substances
Present in a
subject
Particular
accidents
Predicated of
a subject
Substance
universals
(species,
genera)
Nonsubstantial
universals
The Fourfold Division (2)
Predicated of
a subject
Not present
in a subject
Not
predicated of
a subject
Socrates,
Bucephalus
Present in a
subject
Socrates’
paleness
Paleness
Humanity,
animality
The Possibility of Change
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“It is a distinctive mark of substance,
that, while remaining numerically one
and the same, it is capable of admitting
contrary qualities (accidents), the
modification taking place through a
change in the substance itself.”
Example from Physics, 1: “the
unmusical man becomes musical.”
Denials of the Possibility of Change
• Denied by Parmenides and his disciples (the
Eleatic philosophers).
Denials of the Possibility of Change
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Argument from the causal impossibility
of change.
– Any new thing must come from either
being or non-being.
– If it comes from being, it already exists,
and so isn’t new.
– Nothing can come from non-being.
– Consequently, no new thing can come to
be.
Potential and Actual Being
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Aristotle rebuts these arguments by
introducing a distinction between two
kinds of being: potential and actual.
To speak or think of a thing, it must
have at least potential being, not
necessarily actual being.
The Causation of Change
• Change comes from both being and non-being (in
different ways).
• For a change to occur, there must be something
that exists before and after the change (the
substance).
• There must also be the absence or privation of
some accident (e.g., being non-musical).
• The non-musical man becomes musical (i.e., a
musical man). Change begins with a combination
of being (as a substance) and non-being (of an
accident in the substance).
Causation Requires an Agent
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When change happens, there was already a potentiality
for the new state in the changing thing.
Potentialities for new states are rooted in the actual
nature of a thing, not just in what we can imagine or
conceive of.
In addition for a potentiality for change in the thing that
changes (the “patient”), we also need an outside
“agent”, with an active power of producing the change.
This “agent” must exist separately from the “patient”, or
else we could not explain why the change did not happen
sooner: the change happens only when the agent and
patient come into mutual contact (or appropriate
proximity) with one another.
This Applies also to Animals and Persons
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Animals and people may appear to act spontaneously,
with no external agent, but we can in fact always find an
agent-patient pair.
In many cases, the organism is stimulated into action by
some perceived change in the environment.
In ever case, we can find some part of the organism
acting upon some other part: such as molecules in the in
the stomach or heart acting upon neurons, which in turn
act on the brain, stimulating further behavior through
perception of some internal state.
Potentialities always Depend on Actuality
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In a sense, these are complementary notions.
However, actuality is more fundamental than or “prior
to” potentiality, in several ways:
• The potentiality of a thing is always grounded in its
actual nature.
• A potentiality is always a potentiality for some kind of
actuality, not vice versa. Actuality is prior in definition.
• Potentialities are never actualized except by the
presence of actual agents.
As a consequence, a being of pure actuality is possible,
but not a being of pure potentiality.
Proof of God’s Existence: St. Thomas
Aquinas’s “First Way”
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In his writings (Summa Theologica and Summa Contra
Gentiles), St. Thomas draws on Aristotle’s work to
demonstrate the existence of God as the First Agent, a
being of Pure Actuality (with no unrealized potentialities).
Time cannot pass without change, and change cannot
happen without the activity of agents.
When natural, created agents act in time, they pass from
being potentially active to being actually active, from
potentially in contact or proximity with the patient to
being actually so.
Hence, there must always be some “prior” agent that
actualizes this potentiality of the proximate natural
agent.
Aquinas’s First Way
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There cannot be an infinite series of such agents, each
being actualized by the prior one, with no first agent,
since nothing would explain how the whole series moved
from potentiality to actuality
Thus, there must be a first agent which is always active
and always in contact with every created thing, the
ultimate source of all change, and the ultimate driver
behind the forward motion of time itself.
Such a first agent must be omni-present (present
everywhere) and immaterial, and it must be a being of
pure actuality, with no unrealized potentiality.
Such a being must be “beyond” time, influencing
creation by its thought and intention. This must be God.
Isn’t Inertia the Answer?
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Some philosophers argue that Newton’s idea of inertia
is the answer: once in motion, bodies tend naturally to
stay in motion. No First Agent/Mover must continuously
keep them moving at every instant.
Why this is wrong: inertia presupposes the passage of
time. Things tend to move with a constant velocity:
covering the same distance in equal intervals of passing
time.
Thus, inertia cannot explain why change keeps
happening, why time keeps passing.
For this, you need an eternally active, timeless Mover.
The Necessity of Stability
• Heraclitus had said: “All is flux,” and “You
can’t step twice into the same river.”
Suggesting that nothing whatsoever endures
from one moment to the next.
• Aristotle argues that this is impossible.
Change implies that something is changed:
the thing changed must in some respects
endure.
• In simple case: substances endure, accidents
change.
What about Substantial Change?
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There are two kinds of change that
don’t fit Aristotle’s simple model (as
presented in The Categories):
generation (creation), and destruction
of substances.
Aristotle believed that some
substances: plants, animals, perhaps
blobs of pure element or mixture, do
come into and go out of existence.
Aristotle’s Physics, Chapter 1
• In this chapter, Aristotle introduces the notion
of ‘matter’ (hule -- lumber).
• Matter = “the primary substratum of each
thing from which it comes to be without
qualification (I.e., from which it is generated),
and which persists in the result (after the
thing is destroyed).”
• Substratum = that which endures through a
change.
In what sense does the matter
endure?
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Not as actual substance.
For Aristotle, one substance cannot be
composed of, constituted by another
substance or substances. A substance
is a thing that exists in and of and by
itself, not through the existence of
other things.
A simple illustration
Potentiality
Particle A
Particle B
Actuality
Particle A
Generating a Complex Individual
Potentiality
A Particles
Actuality
B complex
A Particles
Parts are Essentially Parts
• The parts of a substance (such as an animal or
plant) are essentially parts: they can exist only as
the organic parts they are. Organic things are
organic all the way down.
• Thus, when the animal consumes food, water or
oxygen, even the microscopic particles cease to
exist and are replaced by corresponding organic
parts.
• When waste is eliminated, the converse process
takes place. Ditto for conception & death.
Aristotelian Matter is Hierarchical
• The residue which would exist at the
animal’s death is the proximate matter of
the animal.
• What if those substances were also
destroyed? Then some further substances
would exist - the more remote matter of the
animal.
• At the ideal limit -- we would reach “prime
matter”.
What would Prime Matter be Like?
• It can never exist as such. Aristotelian matter
always exists in some form or other.
• It is much closer to modern ideas of energy
(or mass-energy) than to Newton’s or
Boyle’s conception of “matter”.
• It lacks even dimensionality and quantity.
• It’s what “survives” through radical
transformations of energy from one form (and
even one quantity) to another.
Form and Matter
• Aristotle’s view is called ‘hylomorphism’ (or
‘hylemorphism’).
• Substances are “composed” of both form
(morphe --- the same word Plato used) and
matter (hule -- Aristotle’s coinage).
• Socrates’ humanity is his form: that by which
Socrates exists, that by which his matter is
his matter (as opposed to an actual corpse).
Form is the Actuality;
Matter is Potentiality
• The “matter” of a substance is its potentiality to produce new
substances, either by extruding parts of itself, or by being utterly
destroyed and leaving behind some residue of itself.
• The “form” of a substance is its actual nature, here and now. The
form explains what active powers and passive potentialities a thing
has.
• This is why a being of pure actuality, like God, must be immaterial.
• Just as actuality is prior to potentiality, so form is prior to matter.
• Thus, it is possible for a substance to exist as pure Form (God, the
angels, the human soul after death and before the resurrection), but it
is impossible for anything to exist as pure, unformed Matter.
The Four “Causes”
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The Material Cause: what is a thing made of?
The Formal Cause: what is the fundamental nature of a
thing? What is it?
The Efficient Cause: what agent brought this thing into
existence?
The Final Cause: what is the end or purpose for which
the thing exists?
• These obviously apply to human artifacts, tools.
• Also to organs.
• Aristotle argues that all four apply universally, to all
substances.
• The most controversial is the last one.
Final Causation
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In the inorganic world: consider cycles, like the water
cycle or rock cycle. Each stage exists “for the sake of”
the next one.
The basic laws of nature are not just regularities (Nancy
Cartwright). They represent the ways things (electrons,
photons) act, their active powers and passive
potentialities.
Powers and potentialities point forward, to a possible
future. This is the final cause. Aquinas: “Every agent acts
for an end, otherwise one things would not follow from the
action of the agent more than another.” (ST I, q44, a4)
Final causation is the “cause of causes”, the fundamental
basis for all explanation.