ACADEMIC TALK
Watch the lecture by Danielle Green on Plato’s Republic – Book 1 below and then complete the tasks.
Plato’s Republic: Book 1
Danielle Green
Your tasks for the Plato Republic Lecture:
Find Plato and Aristotle in the painting below!
What is the meaning behind Plato and Aristotle’s actions in the painting? What is a Socratic Dialogue?
What is a premise? What is a conclusion?
Arguments and Logic
Is this a valid argument?
- All humans are cats.
- Cats are dogs.
- Therefore, humans are dogs.
How about this?
- The sky is blue.
- The cars are moving.
- Therefore, I am on Planet Earth.
Or this?
- There are cats in this building.
- There are no cats in this building.
- Therefore, I am the biggest cheese in all the land.
Only the second argument is not valid.
The first argument is valid since the conclusion follows if you accept the premises that all humans are cats and all cats are dogs, then all humans are dogs also! We can substitute ‘human’, ‘dog’ and ‘cat’ for symbols to help us make this clear:
All xs are ys,
All ys are zs,
Therefore, all xs are zs.
This feature in logic is called logical transitivity.
The third argument is valid because if you accept both that there are cats and that there are no cats, then the sentence ‘there are cats, or I am the biggest cheese in the world’ is true. And since there are also no cats, I conclude that I am the biggest cheese in the world. This principle is called the principle of logical explosion or ex falso quodlibet (from falsity, anything). Formally, a way of putting this is:
X is true.
X is not true.
X or Y.
Therefore, Y. The second argument is not valid because the premises have nothing to do with the conclusion of the argument, nor with each other. Just because the sky is blue, and cars move has nothing to do with whether I am on Earth or not. Premises must have a connection; they must have something to do with whether the conclusion is true or false for an argument to be valid.
The Allegory of the Cave, Republic VII
What does the Allegory of the Cave say about the journey and treatment of philosophers?
What does the Allegory of the Cave say about our world?
Do you agree with its analysis?
Why do you agree/disagree with Plato here?
Justice, Republic I
What is justice?
Cephalus – speaking the truth and giving people what they are owed.
Polemarchus (eventually) – doing good to true friends and not good to true enemies.
Thrasymachus – the advantage of the stronger.
What do you think of the ways that Socrates argues against these definitions?
Can you think of ways of responding to Socrates or helping him argue against these definitions?
What do you make of the ending of Book I?
“The result of this discussion… is that I know nothing, for when I don’t know what justice is, I’ll hardly know whether it is a kind of virtue or not, or whether a person who has it is happy or unhappy.”
(Republic, 354c)
Ask someone around you what they think justice is.
If you agree with them, why?
If not, why do you disagree with them?
Further Reading
Plato’s Republic, Book I – Plato, Republic, Book 1 (tufts.edu)
G. Hourani, 1962. “Thrasymachus’ Definition of Justice in Plato’s “Republic”” in Phronesis 7(2) pp.110-120 thrasymachus_definition_of_justice_in_platos_republic.pdf (warwick.ac.uk)
