11

22

David Hume’s Theory David Hume’s Theory of Knowledgeof Knowledge

(1711-1776)(1711-1776)Scottish EmpiricistScottish Empiricist

33

An Enquiry Concerning An Enquiry Concerning Human UnderstandingHuman Understanding

Foundation of all knowledge is in Foundation of all knowledge is in sensory experiencesensory experience

44

Can we have certain Can we have certain knowledge?knowledge?

YES!YES!

55

Relation of IdeasRelation of Ideas

How our ideas relate to one anotherHow our ideas relate to one another

Analytic TruthsAnalytic TruthsTautologiesTautologies

Mathematical TruthsMathematical Truths

66

Always can involve a contradictionAlways can involve a contradiction

““An unmarried man An unmarried man is notis not a bachelor” a bachelor”

Why is this a contradiction?Why is this a contradiction?

Because of how we define the termsBecause of how we define the terms

77

All other knowledge?All other knowledge?

88

Matters of FactMatters of Fact

Synthetic TruthsSynthetic Truths

Never can involve a contradictionNever can involve a contradiction

We can only have a high degree of We can only have a high degree of probabilityprobability

99

ExampleExample

““The sun will rise tomorrow”The sun will rise tomorrow”

1010

2 Types of Perceptions2 Types of Perceptions

1111

ImpressionsImpressions

From From sense datasense data

ofofmind independent realitymind independent reality

1212

Thoughts / IdeasThoughts / Ideas

FromFromOur memory ofOur memory of

ImpressionsImpressionsoror

ImaginationImagination

1313

Difference between the two?Difference between the two?

Impressions are more lively than Impressions are more lively than thoughts or ideasthoughts or ideas

1414

ExampleExample

Which is more lively:Which is more lively:

Actually burning your fingerActually burning your fingeroror

The memory of burning your finger?The memory of burning your finger?

1515

Empirical Criteria of MeaningEmpirical Criteria of Meaning

1. All meaningful ideas must be traced 1. All meaningful ideas must be traced back to sense impressionback to sense impression

(Experience)(Experience)

1616

2. Ideas and beliefs that cannot be traced 2. Ideas and beliefs that cannot be traced back to sense impression (experience) back to sense impression (experience)

are meaninglessare meaningless

1717

ExampleExample

A golden mountainA golden mountain

A unicornA unicorn

GodGod

1818

How would you explain color How would you explain color to a blind person?to a blind person?

You can’tYou can’t

They have no impression referenceThey have no impression reference

1919

Cause and EffectCause and Effect

2020

2121

Cause and EffectCause and Effect

Cannot be traced back to impressionsCannot be traced back to impressions

It involves no contradictionIt involves no contradiction

2222

For ExampleFor Example

Let’s take the sentence:Let’s take the sentence:

““X causes Y”X causes Y”

Where X and Y are both eventsWhere X and Y are both events

2323

X is the event of billiard ball A X is the event of billiard ball A striking billiard ball Bstriking billiard ball B

Y is the event of billiard ball B moving Y is the event of billiard ball B moving after being struckafter being struck

2424

Question:Question:Is the sentence “X causes Y” analytic?Is the sentence “X causes Y” analytic?

That is to say, is the sentence That is to say, is the sentence ““X does not cause Y” a self-contradiction?X does not cause Y” a self-contradiction?

Like:Like:

““A unmarried male is not a bachelor”A unmarried male is not a bachelor”

2525

Answer:Answer:

NO!NO!

This sentence is not analytic!This sentence is not analytic!

2626

Is this sentence synthetic?Is this sentence synthetic?

It seems that the answer will be yes It seems that the answer will be yes because this is the only alternativebecause this is the only alternative

But Hume had a problem with this But Hume had a problem with this answer too!answer too!

2727

When he analyzed the concept of When he analyzed the concept of causality, he broke it down into three causality, he broke it down into three components:components:

1.1. PriorityPriority2.2. ContiguityContiguity3.3. Necessary ConnectionNecessary Connection

2828

PriorityPriority

Means that X precedes YMeans that X precedes Y

This can be traced back to sense dataThis can be traced back to sense data

2929

ContiguityContiguity

Means that X touches YMeans that X touches Y

This can also be traced back to sense This can also be traced back to sense datadata

3030

Necessary Connection?Necessary Connection?

Means that if X happens, Y Means that if X happens, Y MUSTMUST happen happen

No matter how many times Hume looked No matter how many times Hume looked he could find no necessary connectionhe could find no necessary connection

Therefore, causality cannot be traced Therefore, causality cannot be traced back to sense databack to sense data

3131

Implications?Implications?

Causality means that whenever we say Causality means that whenever we say that one thing (X) causes another thing that one thing (X) causes another thing

(Y)(Y)

We are really only reporting our own We are really only reporting our own EXPECTATIONS EXPECTATIONS

that X will be followed by Ythat X will be followed by Y

3232

This is a psychological fact about us and This is a psychological fact about us and not a fact about the worldnot a fact about the world

Even if X was followed by Y innumerable Even if X was followed by Y innumerable times in the past, times in the past,

that does not justify our claim to know that does not justify our claim to know that it will do so again in the futurethat it will do so again in the future

3333

And we assume that (A) caused (B)And we assume that (A) caused (B)

But all we have seen is two distinct But all we have seen is two distinct events that happen in successionevents that happen in succession

3434

ExampleExample

The rooster always crows just before the The rooster always crows just before the sun risessun rises

Does that cause the sun to rise?Does that cause the sun to rise?NO!NO!

3535

Causality is a matter ofCausality is a matter ofCUSTOMCUSTOM

andandHABITHABIT