This document provides an overview of key concepts from Plato's epistemology and metaphysics. It discusses Plato's view that knowledge pertains to eternal, unchanging forms that exist in the intelligible realm, rather than the particulars of the visible realm which are merely objects of opinion. It also summarizes Plato's idea of an ideal society structured around three classes that map to the three parts of the soul: producers correspond to appetite, auxiliaries to spirit, and philosopher kings to reason.

1. PLATO TERMS

2. Epistemology
The branch of philosophy concerned with
knowledge, belief, and thought.
Epistemological questions include:
What is knowledge?
How do we form beliefs?
Can we know anything?

3. CONSIDER:
What is your own approach to epistemology?
WHAT IS YOUR FIRST PRINCIPLE?
EVIDENCE
SCIENCE
FAITH
SELF-INTEREST
CULTURAL INFLUENCES
WHY?

4. VISIBLE vs. INTELLIGIBLE REALM
The Visible Realm is grasped with our senses. It is
comprised of the particular things we see, hear, smell,
taste, touch around us—the SENSIBLE PARTICULARS. We
cannot “know” anything about these objects; we can only
have opinions.
The Intelligible Realm is an aspect of reality beyond and
more real than what we can see. It cannot be grasped
through the senses but through the intellect. This realm is
comprised of the FORMS and is the realm of TRUTH and
the object of knowledge.

5. FORMS
The unchanging, eternal, absolute entities or truths. These
absolute entities (which are based on concepts, not objects, like
Beauty, Goodness, Sourness) are the cause of all the objects we
experience in the visible realm.
My blue pen is not the absolute blue pen. Conceptually, there is
an ideal blue pen that can never be realized on earth.
The FORM OF THE GOOD is the ultimate form from which all
others are derived. It is the source of intelligibility and of our
capacity to know. It acts in the intelligible realm as the sun in
the visible realm (illuminating/clarifying everything). It is the
ultimate object of knowledge.
By grasping the Form of the Good, one reaches the highest
grade of cognitive activity, understanding, and becomes a
philosopher-king.

6. METAPHYSICS
The philosophical study of the fundamental nature of
things. It is often broken down into the study of BEING
and ORIGINS.
The FORM OF THE GOOD is the ultimate origin for Plato.
CONSIDER:
What are some common beliefs about the ultimate source,
the ultimate origin of everything?

7. Plato considered the soul to be 3 parts:
Appetite
Spirit
Reason

8. APPETITE:
This is man’s desire for food, sex, shelter. It’s
basically encapsulates physical needs/urges, though
those can be necessary desires (the desire to eat to
stay alive), unnecessary desires (the desire to eat a
10 lb. steak 3 times a day), and unlawful desires (the
desire to eat one’s children).
In a just man, the appetite is strictly controlled by
reason and reason’s henchman, spirit.
Plato considered the lowest class of society to be
ruled by this aspect of the soul.

9. SPIRIT
The source of desire for honor, victory, and justice.
Spirit is responsible for feelings of anger and
indignation.
In a just soul, spirit acts as henchman for reason,
ensuring that appetite adheres to reason’s
commands.
In Plato’s ideal society, the peace-keeping or
militaristic class would be motivated by this part of
the soul.

10. REASON
This aspect of the soul lusts after TRUTH. It is the
source of all of our philosophic desires.
The just man is ruled by reason and should therefore
rule over an ideal society.
These men Plato called “philosopher kings.”

11. 3 LEVELS OF PLATO’S IDEAL SOCIETY
PRODUCERS
AUXILIARY
GUARDIANS
These correspond to the 3 parts of the soul.

12. PRODUCERS
All producers had a SPECIALIZTION: they only worked at
the one thing they did best, and they had no other
choices. They consist of the largest class of society which
includes all professions: framers, craftsmen, merchants,
doctors, artists, actors, lawyers, judges. However, they
have no share in ruling.
Because they are ruled by APPETITE (physical
desire/urges), they are not fit to rule. They are only fit
to…
OBEY and WORK

13. AUXILIARY
The warriors responsible for defending the city from
invaders and keeping the peace at home.
They must enforce the convictions/laws of the guardians
and ensure that the producers obey.
Like SPIRIT is the henchman of REASON, the AUXILIARY are
the henchmen of the GUARDIANS.
Because the AUXILIARY are motivated by SPIRIT, they seek
honor, victory, and justice.

14. GUARDIANS
Also known as PHILOSOPHER KINGS, GUARDIANS rule over
Plato’s ideal society.
Because they are motivated by REASON and because they
have achieved an UNDERSTANDING of the FORM OF THE
GOOD, they are the only ones fit to rule.

15. LEVELS of COGNITIVE ACTIVITY
IMAGINATION
BELIEF
THOUGHT
UNDERSTANDING

16. IMAGINATION: The lowest grade of cognitive activity. Mere
images and shadows are seen as the most real things. Ideas
about man and the world come from art (poetry, movies…reality
TV).
BELIEF: The second lowest grade of cognitive activity. The
object of belief is the visible realm rather than the intelligible
realm. A man in a state of belief does not have any access to
the Forms, but instead takes sensible particulars as the most
real things.
THOUGHT: The second highest grade of cognitive activity. It
focuses on the Forms (eternal truths, not just physical objects).
Thought though can only proceed with the crutches of images
and hypotheses (i.e. unproven assumptions).
UNDERSTANDING: The highest grade of cognitive activity
involving pure, abstract reason—Plato considered Math the
highest discipline because it is purely theoretical. This is only
achieved once the Form of the Good is grasped.

17. KNOWLEDGE vs. OPINION
Knowledge can only pertain to eternal, unchanging truths.
I can know that 2+2=4, because this will always be the
case (2 itself is a concept, an interpretation of the data
we see).
Since only eternal, unchanging truths can be the objects
of knowledge, all other truths are relegated to opinion.
Opinion is the highest form of certainty that we can hope
for when it comes to the visible realm, the realm of
sensible particulars.

18. SOPHISTS
During Plato’s day, the Sophists rejected the notion of
objective truth and knowledge, including objective moral
truth. They did not believe in “right” and “wrong.”
Plato wanted to prove the Sophists wrong: to show that
there is such a thing as objective truth, and that we can
have knowledge of this objective truth.
That objective truth simply does not inhabit this realm.

19. BEFORE READING PLATO, WATCH: