1. Plato on Knowledge

2. Plato 429-347 BC 429-347 BC Student of Socrates (469-399) Student of Socrates (469-399) Teacher of Aristotle (384-322) Teacher of Aristotle (384-322) Founded ‘Academy’ Founded ‘Academy’ Wrote Dialogues Wrote Dialogues Theaetetus Theaetetus Republic Republic Meno Meno

3. Theaetetus A late treatment of knowledge A late treatment of knowledge Dismisses two possibilities for knowledge Dismisses two possibilities for knowledge Perception Perception True belief True belief Proposes: True Belief with an Account Proposes: True Belief with an Account To know X is to truly believe X and to have an account of X To know X is to truly believe X and to have an account of X But what is an account? Justification for the belief? But what is an account? Justification for the belief?

4. Theaetetus First possibility: an account is an analysis of how X is composed of simpler parts First possibility: an account is an analysis of how X is composed of simpler parts So no simple thing can be known? So no simple thing can be known? Reject this idea Reject this idea

5. Theaetetus Second possibility: an account is a catalogue of the component parts Second possibility: an account is a catalogue of the component parts But you can list the parts of a chariot without having an understanding of the chariot itself. But you can list the parts of a chariot without having an understanding of the chariot itself. Reject this idea Reject this idea

6. Theaetetus Third possibility: an account is an identification of the distinguishing characteristic Third possibility: an account is an identification of the distinguishing characteristic To know X about the sun is for X to be a true belief and you can identify the sun as, say, the brightest object in the sky To know X about the sun is for X to be a true belief and you can identify the sun as, say, the brightest object in the sky But this means there is always something else to know before you can know any X But this means there is always something else to know before you can know any X Reject this idea Reject this idea

7. Theaetetus All possibilities are eliminated. All possibilities are eliminated. Aporia again? Aporia again? Plato has another theory from previous dialogues Plato has another theory from previous dialogues

8. The Theory of the Forms There is a realm of real things that are both non- physical and non-mental There is a realm of real things that are both non- physical and non-mental Things in this realm are the ‘Forms’ (ideas in Greek) of things in the physical realm Things in this realm are the ‘Forms’ (ideas in Greek) of things in the physical realm Things in the physical realm are what they are because they are in some way connected to their Forms Things in the physical realm are what they are because they are in some way connected to their Forms We can know things only through ‘acquaintance’ with their Forms We can know things only through ‘acquaintance’ with their Forms

9. The Theory of the Forms Forms explain the possibility of general terms Forms explain the possibility of general terms We can call many things by one name We can call many things by one name All things which are dogs we can call a dog. All things which are dogs we can call a dog. There must be something which is: There must be something which is: 1. Common to all things called by a general term 2. Distinctive of all those things This thing is This thing is 1. Not physical – not all dogs have any physical trait 2. Recognisable by us – but not by our senses

10. The Theory of the Forms Forms explain the possibility of judgement Forms explain the possibility of judgement All judgement is a type of comparing All judgement is a type of comparing ‘This is a dog’ means I am comparing ‘this’ to some standard of dogginess ‘This is a dog’ means I am comparing ‘this’ to some standard of dogginess The standard can’t be another dog – else I have to first judge that that is a dog, and so on The standard can’t be another dog – else I have to first judge that that is a dog, and so on The standard can’t be my idea of a dog – it is the idea of a dog only because it is judged to represent dogs accurately. So I still need to judge its dogginess; and so on. The standard can’t be my idea of a dog – it is the idea of a dog only because it is judged to represent dogs accurately. So I still need to judge its dogginess; and so on.

11. The Theory of the Forms Forms explain the possibility of judgement Forms explain the possibility of judgement The standard of ‘dog’ can’t be physical or mental The standard of ‘dog’ can’t be physical or mental It is metaphysical It is metaphysical It is that in virtue of which It is that in virtue of which 1. All things properly called ‘dog’ are properly so called 2. Only things properly called ‘dog’ are properly so called We call it the Form of dog, or dog-in-itself, … We call it the Form of dog, or dog-in-itself, …

12. The Theory of the Forms How do Forms relate to their particulars? How do Forms relate to their particulars? 1. 1. Transcendence: there is far more to the Forms than the particular things which fall under them 2. 2. Immanence: the Forms are present in their particulars, but not in a way that we can perceive through our senses

13. The Theory of the Forms How do we come to know of them? How do we come to know of them? 1. Not by our external senses (perception) 2. Not by our internal sense (awareness) 3. But by intellectual perception or awareness of the understanding (Whatever those might be)

14. The Theory of the Forms Who is capable of knowing them? Who is capable of knowing them? We are all able to use the term ‘dog’ correctly, We are all able to use the term ‘dog’ correctly, So we are all ‘intellectually aware’ of the Form of Dog So we are all ‘intellectually aware’ of the Form of Dog Dog is the Form of a mundane thing – it is a ‘lower’ Form Dog is the Form of a mundane thing – it is a ‘lower’ Form ‘Higher’ Forms are of things such as Triangle, Courage, Equal, Noble, … ‘Higher’ Forms are of things such as Triangle, Courage, Equal, Noble, … Only those trained as intellectuals can ‘perceive these in their understanding’ Only those trained as intellectuals can ‘perceive these in their understanding’

15. How we Know How do we come to know the higher Forms? How do we come to know the higher Forms? Plato gives an example in the Meno Plato gives an example in the Meno A slave is taught to double a square A slave is taught to double a square Slave thinks he knows but gives the wrong answer at first before Socrates begins to question him Slave thinks he knows but gives the wrong answer at first before Socrates begins to question him This also shows the value of elenchus This also shows the value of elenchus Socrates then gets the slave to give the right answer Socrates then gets the slave to give the right answer Since the slave only answered questions, he must have known how to double a square already Since the slave only answered questions, he must have known how to double a square already

16. The Allegory of the Cave What is the difference between how normal people see the world and how philosophers see it? What is the difference between how normal people see the world and how philosophers see it?

17. The Objects of Knowledge Only the Forms are objects of real knowledge Only the Forms are objects of real knowledge They are permanent, unchanging, always true They are permanent, unchanging, always true What is learnt through the senses is ‘opinion’ What is learnt through the senses is ‘opinion’ It is impermanent, changeable, sometimes true and sometimes not It is impermanent, changeable, sometimes true and sometimes not Plato is contradicted by Aristotle, as we shall see