Knowledge From Reason

Question 1

What is priori knowledge?

Answer 1

Knowledge that can be acquired without experience of the external world, through thought alone

E.g., working out what 5 + 4 is

Question 2

What is a posteriori knowledge?

Answer 2

Knowledge that can only be acquired from experience of the external world

E.g., doing an experiment to discover the temperature at which water boils

Question 3

Analytic vs Synthetic Truth

Answer 3

Analytic Truth - True in virtue of the meaning of the words
E.g., “A bachelor is an unmarried man” or “triangles have three sides”

Synthetic Truth - True in virtue of how the world is
E.g., “Grass is green” or “water boils at 100°c”

Question 4

What is (rational) intuition?

Answer 4

A priori method for gaining knowledge:

The ability to know something is true just by thinking about it

E.g. Descartes’ cogito argument (I doubt therefore I think therefore I am)

Question 5

What is deduction?

Answer 5

A priori method for gaining knowledge

A method of deriving true propositions from other true propositions (using reason)

E.g. You can use deduction to deduce statement 3 from statements 1 and 2 below:
1. If A is true then B is true
2. A is true
3. Therefore, B is true

Question 6

Empiricism vs Rationalism

Answer 6

Empiricism says all a priori knowledge is of analytic truths (i.e. there is no synthetic a priori knowledge)

WHEREAS

Rationalism says not all a priori knowledge is of analytic truths (i.e. there is at least one synthetic truth that can be known a priori using intuition and deduction)

Question 7

The Three Synthetic Truths Descartes Argues For

Answer 7

“I exist”
“God exists”
“The external world exists”

Question 8

Descartes - Three Waves of Doubt

Answer 8

Illusion
Dreaming
Deception

Question 9

Three Waves of Doubt: Illusion

Answer 9

I can doubt the reliability of my sense experience as it has deceived me in the past. For example, a pencil in water may look crooked even though it isn’t.

Question 10

Three Waves of Doubt: Dreaming

Answer 10

I might believe I’m looking at a computer screen, but if I’m simply dreaming that I am, then my belief is mistaken.

Question 11

Three Waves of Doubt: Deception

Answer 11

Basic ideas are still there in illusions and dreams such as 1+1=2 but Descartes says basic ideas can be doubted if you are being deceived.
E.g., I might believe I’m looking at a computer screen, but if I’m simply dreaming that I am, then my belief is mistaken.

Question 12

Position of Extreme Doubt

Answer 12

Global Scepticism

Question 13

Cogito Ergo Sum

Answer 13

I think therefore I am

Descartes — the only thing he can know for certain is:

Dubito, ergo cogito, ergo sum = I doubt, therefore I think, therefore I am

Descartes cannot doubt that he exists

Question 14

Clear and Distinct Ideas

Answer 14

Recognition that it’s impossible for the proposition to be false

Descartes claims that his certainty in the proposition ‘I exist’ is due to the fact that it is a clear and distinct idea

Question 15

Descartes’ 3 arguments for existence of God

Answer 15

Descartes gives several arguments for the existence of God using intuition and deduction:

• Descartes’ ontological argument
• Descartes’ cosmological argument
•The trademark argument

Question 16

Summary of Descartes’ Trademark Argument

Answer 16

1. I have the concept of God
2. My concept of God is the concept of something infinite and perfect
3. But I am a finite and imperfect being
4. The cause of an effect must have at least as much reality as the effect
5. So, the cause of my concept of God must have as much reality as what the concept is about
6. So, the cause of my idea of God must be an infinite and perfect being
7. So, God exists

Question 17

Problem of The Trademark Argument

Answer 17

The concept of God is not innate - If concept of God comes from experience, as Locke argues, then Descartes’ argument is not entirely a priori and so fails to establish rationalism

Question 18

Hume’s Fork

Answer 18

We can only have knowledge of:
- Relations of ideas
- Matters of fact

• Relations of ideas = a priori and analytic
• Matters of fact = a posteriori and synthetic

Question 19

What is innate knowledge?

Answer 19

Knowledge you’re born with and so doesn’t require experience (a posteriori) to be known

Innate knowledge is a priori knowledge

Question 20

Plato: Meno

Answer 20

Plato argues that all learning is a form of recalling knowledge from before we’re born. In other words, we’re born with innate propositional knowledge and we just need to remember it.

To prove his theory, Plato shows how Meno’s slave – a boy who has never been taught geometry – is able to understand a geometry proof.

Question 21

Necessary truth

Answer 21

Leibniz argues that our knowledge of necessary truths must be innate.

Necessary truth= What must be the case
• True in every possible world
• E.g. “2+2=4” is true in every possible world – it must always be true

Question 22

Contingent truth

Answer 22

Contingent truth = What is the case
• Could have been false in some other possible world
• E.g. “this website exists” is true but it would be false in some other possible world where I didn’t make it

Question 23

What does Leibniz argue?

Answer 23

Leibniz argues knowledge of necessary truths is innate. We know them by paying close attention to “what is already in our minds”.

Question 24

Arguments against innate knowledge (Locke’s arguments)

Answer 24

1. Innate knowledge would be universal
> Locke argues if we did have innate knowledge then every human would have such knowledge
Locke argues children and ‘idiots’ do not possess such knowledge – they don’t know the theorems of geometry, for example. So, this knowledge is not universal and therefore not innate.

2. Argument against innate concepts
Locke argues against the existence of innate concepts. The argument is that propositional knowledge relies on concepts. E.g., you can’t know that “1+1=2” without first having the concepts “1” ,“+”, and “2”. So, if Locke succeeds in disproving the existence of innate concepts, he will also succeed in disproving the existence of innate knowledge.

Question 25

Normal incredulity/ordinary doubt

Answer 25

Doubts that occur in our everyday lives
E.g., you might be unsure whether a friend’s birthday is the 17th or the 18th of August

Question 26

Examples of global sceptical scenarios in philosophy and popular culture

Answer 26

Descartes’ evil demon
The Matrix
The simulation hypothesis
Perfect virtual reality
Brain in a vat