1. Knowledge & Truth Book V
Plato - Republic
Knowledge & Truth
Book V

2. "Who are the true philosophers?"
“Lovers of the vision of truth"
But what does this mean?
How do we know truth?
1st step: distinguish sense from intellect.

3. Ideas and Things Intellect
Beauty is opposite of ugliness, just of unjust, good of evil, and so on.
Each of these is one thing.
This is not the same as enjoying beautiful things.
Sense
Such sense knowledge is like dreaming.
Beauty, goodness the just seem to change.
The problem: "the beautiful will in some point of view be found ugly."

4. Ideas and things ~ cont’d
Likewise with other opposites.
A large dog is smaller than a small elephant!

5. Ideas and Things ~ cont’d
If everything is true ‘in some point of view,’ then those same things are false 'in some point of view.'
That is to say...
Nothing is absolutely true.
Knowledge is relative.

6. Plato's answer
Things we sense, which can be beautiful, large, or just 'in a point of view,' are halfway between being and non-being.
Those who know these things without knowing absolute ideas have opinion rather than knowledge.
They are lovers of opinion, not philosophers.

7. Image and Reality Book VI
Plato - Republic
Image and Reality
Book VI

8. Absolute ideas and things
What does - say - a lovely rose have to do with absolute beauty?
Socrates begins by distinguishing the visible and the intelligible.

9. The “Divided Line”
Ascent from images through perceptions through hypotheses to first principles (ideas).
Four Conditions in the soul:
Understanding
Thought (mathematical hypothesis)
Belief or opinion
Imaging (picture-thinking)
Human knowledge moves from pictures, images and analogies to perfect understanding, but how?

10. The “Divided Line” 1st section - images, shadows, reflections
2nd section - animals, things
Things in the 1st section copy those in the 2nd.
3rd section - figures from the visible realm: mathematics.
4th section - no images but ideas themselves
Visible
Intelligible

11. Republic – Book VII
The Cave

12. The Cave

13. The Cave and the Line Line Cave The shadows Imagination
Belief
Thought
Understanding
The shadows
The objects on the wall
Reflections and shadows
Objects outside the cave

14. The Interpretation (517b-c)
The cave itself is a metaphor for knowledge of the sensible world.
The entire realm of sense is only apparent knowledge.
The fire – source of light within the Cave – represents the sun.
This corresponds to the lower two sections of the Line.

15. The Interpretation (cont’d)
The world outside the Cave is the realm of intelligence.
1st – discursive thought about mathematical entities.
2nd – understanding of the Forms themselves.
The source of all these is the Good.
The Good is “the cause of all that is correct and beautiful in anything.” (517c)

16. Application to Education
Education: not putting knowledge into ignorant souls but turning them towards the brightest region of being (518c).
The art of conversion of souls (518d).