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Introduction to Philosophy

WHAT IS

KNOWLEDGE? (AND DO WE HAVE ANY?)

Professor Duncan Pritchard FRSE duncan.pritchard@ed.ac.uk

www.ppls.ed.ac.uk/people/view/duncan-pritchard-frse

Ren Descartes (1596-1650)

Structure of the Lecture

Part One: What is Knowledge? Part Two: Do We Have any Knowledge?

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Part One:

What is Knowledge?

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Propositional versus Ability Knowledge

Knowledge-that: Knowing that Paris is the

capital of France. Knowing that the earth

orbits the sun. Knowing that one has

toothache.

Knowledge-how: Knowing how to drive. Knowing how to play

piano. Knowing how to beat the

stock market.

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Two Conditions for Propositional Knowledge

One can know a proposition only if: (i) That proposition is true;

(ii) One believes that proposition.

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Knowing versus Getting it Right

Two Intuitions About Knowledge

The Ability Intuition

Knowledge requires getting it right through

ones ability

The Anti-Luck Intuition

Knowledge requires getting it right in a non-

lucky way

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The Classical Account of Knowledge

One can know a proposition if, only if: (i) That proposition is true;

(ii) One believes that proposition; (iii) Ones belief is justified.

Plato (427-347 BC)

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Gettier Counterexamples

Examples of justified true belief where the true belief in question is just too

lucky to count as knowledge

Edmund Gettier (b. 1927)

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A Gettier-Style Case

The Stopped Clock

You believe that the time is 7.28am. You are justified in believing that the

time is 7.28am. It is true that it is 7.28am.

But you dont know that its 7.28am because, unbeknownst to you, what you are looking at is a stopped clock. A stopped clock, yesterday.

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Another Gettier-Style Case

The Sheep

You believe that there is a sheep in the field. You are justified in believing that there is a sheep in the field.

It is true that there is a sheep in the field. But you dont know that there is a sheep in the field because,

unbeknownst to you, what you are looking at is a big sheep-shaped rock which is obscuring from view a sheep hidden behind.

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A Formula for Inventing Gettier-Style Cases

Step One Take a belief that is formed in such a way that it would usually result in a false belief, but which is

justified nonetheless.

Step Two Make the belief true, albeit for reasons that have

nothing to do with the subjects justification.

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Patching up the Classical Account:No False Lemmas

One can know a proposition if, only if: (i) That proposition is true;

(ii) One believes that proposition; (iii) Ones belief is justified;

(iv) Ones belief is not based on any false assumptions (or lemmas).

Keith Lehrer (b. 1936)

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Two Questions Raised by Gettier-Style Cases

(1) Is justification even necessary for knowledge?

(2) How does one go about eliminating knowledge-undermining luck?

Part One Conclusions

Knowledge is not justified true belief. Nor is knowledge justified true belief plus

some obvious extra condition. So what is knowledge?

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Part Two

Do We Have any Knowledge?

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Radical Scepticism Radical scepticism is the view that

knowledge (at least of the world around us) is impossible.

Sceptics make use of sceptical hypotheses, scenarios where

everything is as it usually appears to be, but where we are being radically

deceived.

The sceptic says that we cannot rule-out sceptical hypotheses, and thus argues that we are unable to know anything about

the world around us.

Ren Descartes (1596-1650)

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The Brain-in-a-Vat Sceptical

Argument

1. I dont know that Im not a brain-in-a-vat.

2. If I dont know that Im not a brain-in-a-vat, then I dont know very much.

C. So, I dont know very much.

Brains-in-Vats

Question: Why dont we know that were not brains-in-vats? Answer: Because we cant tell the difference!

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Brains-in-Vats and Everyday Knowledge

So even if we dont know that were not brains-in-vats, so what?

But if you were a brain-in-a-vat, then you wouldnt have hands (since brains-in-vats are handless by

definition). So how do you know that you have hands?(And if you dont know this, what do you know?)

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Epistemic Vertigo

It is certainly part of the human condition that we are fallible

creatures. But perhaps, once we reflect on the matter (and thus reflectively ascend), we realise

that there is more than just fallibility at issue here. Maybe we simply dont know as much as we

typically suppose.

Part Two Conclusions

Radical scepticism is the view that we know very little, if anything, about the world around us.

Radical scepticism makes use of sceptical hypotheses, which are scenarios indistinguishable from ordinary life but where we are radically in error.

It seems that if we cannot rule-out these hypotheses, then much of what we think we know is under threat.

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Further Reading

I explore these issues about the nature and

extent of knowledge in my introductory textbook, What is This Thing Called Knowledge? (Routledge).

See especially parts 1 & 3.

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Thank You For Listening!

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