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Theory of Knowledge Theory of Knowledge

Theory of Knowledge - PowerPoint Presentation

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Theory of Knowledge - PPT Presentation

TOK Lecture 7 Ways of Knowing Reason Part 1 What is reasoning And how does it lead to knowledge What is reasoning A possible answer reasoning is the mental processing of information But not all mental processing ID: 413573

theory reasoning inference deductive reasoning theory deductive inference knowledge inductive premise conclusion mental induction experience reliable information processing reason

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Slide1

Theory of KnowledgeTOK

Lecture 7: Ways of Knowing - ReasonSlide2

Part 1: What is reasoning? And, how does it lead to knowledge?Slide3

What is reasoning?

A possible answer: reasoning is the mental processing of information.

But, not all mental processing

of information counts

as reasoning.

The transformation of the electrical impulses sent down the optic nerve to the brain into a mental image is an example of mental processing of information.

But it is surely not an example of reasoning.

Does only the mental processing of

propositional

information (information that comes in the form of

statements

) counts as reasoning?

What about spatial reasoning?Slide4

What is an inference?

Drawing an inference involves deriving a conclusion from a premise or set of premises

.

Premise = a

statement

that supports/acts as a basis form/provides evidence for another statement.

Conclusion = a

statement

that is supported by one or more premises.

The

process of drawing inferences is very important

in understanding how

reasoning can lead to knowledge

i.e.,

h

ow

reasoning can count as a “way of

knowing

”.Slide5

Two kinds of inference

Deductive inferences

– when successful: if the premises are true, then the conclusion

has to be true

.

Example 1:

(Premise 1) Steve is a bachelor.

(Conclusion) Steve is not married to Sally

.

Example 2:

(

Premise 1

) All ravens are black

(

Premise 2

) X is a raven

(

Conclusion)

X is

blackSlide6

Two kinds of inference

Non

-

deductive inferences

– Even when successful, the truth of the premises makes the conclusion likely, but not certain.

Example 1:

(Premise 1) The window of my car is broken, and my laptop – which I left on the back seat – is missing.

(Premise 2) The best available explanation of this state of affairs is that someone has broken into my car and stolen my laptop.

(Conclusion) Someone has broken into my car and stolen my laptop

.

Example 2:

(

Premise 1

) Most ravens are

black.

(

Premise 2

) X is a

raven.

(

Conclusion)

X is

black.Slide7

Part 2: The relationship between reason and experienceSlide8

Scientific Reasoning

Natural science is considered to be

an

area of knowledge

in which reason

(

a

way of knowing

) and experience (

another way of knowing

) come together.

But how does this work?Slide9

Inductive reasoning/inference

When philosophers first started thinking about scientific reasoning, they took the process to be

inductive

.

What is inductive reasoning?

Reasoning from particular observations/experiences to general conclusions about the world.

Examples

:

All tigers

observed so far

have been

stripy

. T

herefore,

all tigers are stripy

.

The sun

has always been observed

to rise in the eastern sky. Therefore, the sun rises in the eastern sky every morning (including tomorrow morning).

The fallibility of induction

Inductive reasoning is a form of

non-deductive

reasoning.

The mere fact that all X’s so far observed have been Y does not make it certain the all X’s are Y: All swans observed by Europeans up until the 18

th

century were white!Slide10

Inductive reasoning/inference

Hume’s problem of induction.

The sun has always risen in the east in the morning.

Therefore, the sun will rise in the east tomorrow morning.

But, how do we know that inductive reasoning is reliable

?

Surely we are not justified in making a particular inductive inference unless we are justified in believing that induction, more generally, is a reliable process of reasoning.

We know that induction is reliable because induction has

always

proved

reliable in the past.

Uh oh, we are using inductive reasoning to justify the use of inductive reasoning!

This is like

trying to find

out if Bob is a reliable witness by asking Bob himself.Slide11

Hypothetico-Deductive Reasoning

What is it?

This is where you:

(1) Come up with a hypothesis/theory

(2) Work out what the empirical consequences of the theory will be.

(3) Conduct experiments/observations and see if the results match those predicted by the theory.

Example

:

Einstein’s relativity theory entails – amongst other things - that nothing can travel faster than the speed of light.

If we fail to observe anything travelling faster than the speed of light – or doing anything

else that contradicts the theory – then the theory stands.

If

we do observe some event that the theory says is impossible, the theory falls.Slide12

Hypothetico-Deductive Reasoning

Advantages of the

hypothetico

-deductive approach:

Gets us around the problem of induction

We don’t need to assume that the future will be like the past.

If a theory makes a prediction and the prediction is not borne out, then the theory is proven false, and that is that.

Disadvantages

:

Only allows for falsification, never for absolute verification.

The fact that the predictions generated by a theory have come true so far does not mean that this will continue for ever.

E.g. – Scientists have not yet made a reliable observation of an object travelling faster than the speed of light, but such an observation might be made at some time in the future. Slide13

A priori reasoning: pure reason

A priori

reasoning involves reasoning to conclusions in a way that does not involve any reliance on experience.

The example of mathematical reasoning:

Most mathematical reasoning involves the drawing of inferences from mathematical axioms or principles.

But how are the principles

themselves supported

/justified?

By experience

? Surely not.

Because to understand them is to see that they simply must be true?

This answer actually seems more plausible.Slide14

Knowledge without reasoning?

Sometimes it looks as though we can gain knowledge is a way that doesn’t rely on other knowledge.

In fact, it seems like this must be the case: if all knowledge relies on other knowledge for support, then the chains of support will go on forever.

Self-evidence in logic and mathematics

Do you need a reason to accept that 1 + 1 = 2?

If you know what “1 + 1 = 2” means, then you know that it is true, right?

Basic empirical beliefs

What about beliefs about the contents of experience?

E.g. “I have a pain in my leg” or “I see something red”Slide15

Discussion questions for this week

What is reasoning, and how does it differ from other kinds of mental processing of information?

What is an inference?

What is the difference between deductive and non-deductive inference? Can you come up with some examples of each?

What reasons do we have to prefer the hypothetic-deductive account of scientific reasoning to the inductive account?

Can there be reasoning without experience, or knowledge without reasoning?Slide16

Journal entry due

week 1, Term 2, and reading.

What is the difference between deductive and non-deductive inference?

Come

up with

two

examples of

each.

Reading for the start of term 2:

Nicholas

Alchin

,

Theory of Knowledge

, pp. 72-91