Lecture 1 - Plato on relativism
Theaetus comes up with the claim ‘knowledge is perception’ (p. 205). Socrates converts this
claim into the homo-mensura doctrine of Protagoras, holding the idea that man is the measure
of everything: “Man, he says, is the measure of all things, of the existence of things that are,
and of the non-existence of things that are not (...)” (p. 205).
‘Knowledge is perception’ can be explained as follows:
a) How things appear to an individual, is how they are to that individual.
b) The equivalence of ‘Y appears F to X’ is ‘X perceives Y as F’.
>Example: to individual A, the wind feels cold, and to individual B the wind feels hot. This
means that the wind is cold to individual A and is hot to individual B.
Because of the theory of Flux, there is a perceptual infallibility. The theory of Flux means
that there is an interaction between the viewer’s eyes and the object, which creates an
unrepeatable and unique perception, because everything is continuously in motion.
From this it follows that perception can thus not be conflictive, and that there is truth
in everyone’s belief.
After explaining this claim, Socrates goes on to refute it. The critiques are:
a) Are people the measure of their own truth? If so, how could one individual, like
Protagoras himself, be wiser than another?
The answer is that one cannot be wiser than someone else, but instead can be better
able to clarify the way things appear to people as some sort of expertise.
b) The self-refutation argument:
1) Some people believe that there are false beliefs. So, if all beliefs are true (acc. to
Protagoras’ doctrine), there are false beliefs.
2) From 1 follows that if there are people who believe that Protagoras is wrong about
man being the measure of all things, Protagoras must agree with them, because their
disagreement is a truth.
This disputes the homo-mensura doctrine.
, Lecture 2 - Aristoteles on substance
A substance is an individual thing that can exist by itself; it’s an independent entity. Aristotle
has distinguished ways of talking about a substance by making ten categories, as explained in
his Categories.
What can be said of a substance is distinguished in two groups:
a) said of what a subject is (what they are)
b) said of what is in a subject (what they have)
These qualities are based upon the substance and depend upon the substance. If the substance
ceases to exist, so do the qualities.
There is a distinction between primary and secondary substances.
a) A primary substance is an individual, which is the most independent.
b) A secondary substance is a species or genus, which is a higher level of abstraction and
is dependent on the primary substance (the individual).
‘To predicate’ (predication) means to say something of a substance or subject. This statement
is either true or false.
For a sentence to be true or false, it must at least include a predicate and an object. Example:
a fast horse, a tall man, a big house.
The constituents can consist of nouns (and their derivatives) and verbs.
Aristotle abbreviates ‘predicate’ as P, and ‘subject’ as S. A sentence would be ‘S is P’. This
sentence is to be read as ‘S is/exists as a P’.
A predication would be true if:
1) S and P belong to the same category, or
2) S refers to a substance and P to another category.
The ten categories are:
1. Substance
2. Quantity
3. Quality
4. Relative
5. Where
6. When
7. Being arranged
8. Having on
9. Doing
10. Being affected
Attributes are things that belong to a substance (so, anything from categories 2-10) that are
optional for that substance to have, or are changeable. It used to be called ‘accidents’.
Theaetus comes up with the claim ‘knowledge is perception’ (p. 205). Socrates converts this
claim into the homo-mensura doctrine of Protagoras, holding the idea that man is the measure
of everything: “Man, he says, is the measure of all things, of the existence of things that are,
and of the non-existence of things that are not (...)” (p. 205).
‘Knowledge is perception’ can be explained as follows:
a) How things appear to an individual, is how they are to that individual.
b) The equivalence of ‘Y appears F to X’ is ‘X perceives Y as F’.
>Example: to individual A, the wind feels cold, and to individual B the wind feels hot. This
means that the wind is cold to individual A and is hot to individual B.
Because of the theory of Flux, there is a perceptual infallibility. The theory of Flux means
that there is an interaction between the viewer’s eyes and the object, which creates an
unrepeatable and unique perception, because everything is continuously in motion.
From this it follows that perception can thus not be conflictive, and that there is truth
in everyone’s belief.
After explaining this claim, Socrates goes on to refute it. The critiques are:
a) Are people the measure of their own truth? If so, how could one individual, like
Protagoras himself, be wiser than another?
The answer is that one cannot be wiser than someone else, but instead can be better
able to clarify the way things appear to people as some sort of expertise.
b) The self-refutation argument:
1) Some people believe that there are false beliefs. So, if all beliefs are true (acc. to
Protagoras’ doctrine), there are false beliefs.
2) From 1 follows that if there are people who believe that Protagoras is wrong about
man being the measure of all things, Protagoras must agree with them, because their
disagreement is a truth.
This disputes the homo-mensura doctrine.
, Lecture 2 - Aristoteles on substance
A substance is an individual thing that can exist by itself; it’s an independent entity. Aristotle
has distinguished ways of talking about a substance by making ten categories, as explained in
his Categories.
What can be said of a substance is distinguished in two groups:
a) said of what a subject is (what they are)
b) said of what is in a subject (what they have)
These qualities are based upon the substance and depend upon the substance. If the substance
ceases to exist, so do the qualities.
There is a distinction between primary and secondary substances.
a) A primary substance is an individual, which is the most independent.
b) A secondary substance is a species or genus, which is a higher level of abstraction and
is dependent on the primary substance (the individual).
‘To predicate’ (predication) means to say something of a substance or subject. This statement
is either true or false.
For a sentence to be true or false, it must at least include a predicate and an object. Example:
a fast horse, a tall man, a big house.
The constituents can consist of nouns (and their derivatives) and verbs.
Aristotle abbreviates ‘predicate’ as P, and ‘subject’ as S. A sentence would be ‘S is P’. This
sentence is to be read as ‘S is/exists as a P’.
A predication would be true if:
1) S and P belong to the same category, or
2) S refers to a substance and P to another category.
The ten categories are:
1. Substance
2. Quantity
3. Quality
4. Relative
5. Where
6. When
7. Being arranged
8. Having on
9. Doing
10. Being affected
Attributes are things that belong to a substance (so, anything from categories 2-10) that are
optional for that substance to have, or are changeable. It used to be called ‘accidents’.
