The Legacy of Ancient Greek
Philosophy
Prof. Rob Koons
St. Louis King of France
May 28, 2014
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”.
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
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.
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). Zeno (the creator of
the famous paradoxes, like Achilles and the
tortoise) was one of these.
• Argument from the impossibility of thinking of
the non-existent. Change involves a
transition from non-being to being (or vice
versa). However, it is impossible for some
thing to have non-existence.
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 - 1
• 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.
Causation Requires and Agent - 2
• 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 every 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.
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.
Generating & Destroying a
Complex Individual Substance
Potentiality
A Particles
Actuality
B complex
A Particles
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.
Pure Form
• 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 human soul can exist after death because
its pure intellectual functions (unlike the
functions of non-rational animality, like
sensation) don’t require physicality in their very
definition.
Rejecting Dualism
• Nonetheless, before death (and after the
Resurrection) human beings are (like other
animals) body-soul (or matter-form) composites.
• The rational soul acts as the form of the body –
fully responsible for the body’s being (in
actuality) a living, organic thing.
• Leads naturally to the “theology of the body” (as
John Paul II put it). What happens to the body
has spiritual significance – the body’s isn’t a
mere external contraption attached to an
essentially immaterial human being.
The Four “Causes”
• 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.
Implications of Final Causation
• Biology is thoroughly teleological: ‘genes’,
‘enzymes’, ‘cells’, ‘organs’ – all are defined in
terms of their function.
• The natural function of the human intellect is
the basis of the distinction between reason &
madness, knowledge & opinion, science &
pseudo-science.
• The natural function of the human will is the
basis of ethics and political philosophy: the
human person is naturally ordered to the life of
justice and virtue.