l21

Lecture 21 Truth

4 December 2014

Plan

1. Admin stuff: final, etc.

Plan

1. Admin stuff: final, etc. 2. Truth

Plan

1. Admin stuff: final, etc. 2. Truth 3. Teaching evals

Truth and falsehood

I

Truth and falsehood are properties of propositions

Truth and falsehood

I I

Truth and falsehood are properties of propositions A proposition is something that says that things are in a certain way.

Truth and falsehood

I I I

Truth and falsehood are properties of propositions A proposition is something that says that things are in a certain way. Let p be a proposition. Then,

Truth and falsehood

I I I

Truth and falsehood are properties of propositions A proposition is something that says that things are in a certain way. Let p be a proposition. Then, I

p is true if things are as p says they are, and

Truth and falsehood

I I I

Truth and falsehood are properties of propositions A proposition is something that says that things are in a certain way. Let p be a proposition. Then, I I

p is true if things are as p says they are, and p is false, otherwise.

Truth and falsehood

I I I

Truth and falsehood are properties of propositions A proposition is something that says that things are in a certain way. Let p be a proposition. Then, I I

I

p is true if things are as p says they are, and p is false, otherwise.

p, for example:

Truth and falsehood

I I I

Truth and falsehood are properties of propositions A proposition is something that says that things are in a certain way. Let p be a proposition. Then, I I

I

p is true if things are as p says they are, and p is false, otherwise.

p, for example: I

let p be the proposition expressed by “la neige tombe”

Truth and falsehood

I I I

Truth and falsehood are properties of propositions A proposition is something that says that things are in a certain way. Let p be a proposition. Then, I I

I

p is true if things are as p says they are, and p is false, otherwise.

p, for example: I I

let p be the proposition expressed by “la neige tombe” then p says that snow is falling, and

Truth and falsehood

I I I

Truth and falsehood are properties of propositions A proposition is something that says that things are in a certain way. Let p be a proposition. Then, I I

I

p is true if things are as p says they are, and p is false, otherwise.

p, for example: I I I

let p be the proposition expressed by “la neige tombe” then p says that snow is falling, and p is true if snow is falling, and p is otherwise false

Belief and truth I

Belief is a relationship between a person and a proposition

Belief and truth I I

Belief is a relationship between a person and a proposition A person’s belief is their representation of how the world is

Belief and truth I I I

Belief is a relationship between a person and a proposition A person’s belief is their representation of how the world is Belief and truth are not the same thing

Belief and truth I I I

Belief is a relationship between a person and a proposition A person’s belief is their representation of how the world is Belief and truth are not the same thing I

Not every true proposition is believed by any one person

Belief and truth I I I

Belief is a relationship between a person and a proposition A person’s belief is their representation of how the world is Belief and truth are not the same thing I I

Not every true proposition is believed by any one person Probably every person believes some propositions which are false

Belief and truth I I I

Belief is a relationship between a person and a proposition A person’s belief is their representation of how the world is Belief and truth are not the same thing I I

I

Not every true proposition is believed by any one person Probably every person believes some propositions which are false

Belief is relative to a person, but truth is not

Belief and truth I I I

Belief is a relationship between a person and a proposition A person’s belief is their representation of how the world is Belief and truth are not the same thing I I

I

Not every true proposition is believed by any one person Probably every person believes some propositions which are false

Belief is relative to a person, but truth is not I

Let p be the proposition that the earth is at most 10,000 years old

Belief and truth I I I

Belief is a relationship between a person and a proposition A person’s belief is their representation of how the world is Belief and truth are not the same thing I I

I

Not every true proposition is believed by any one person Probably every person believes some propositions which are false

Belief is relative to a person, but truth is not I

I

Let p be the proposition that the earth is at most 10,000 years old Pat Buchanan believes p, but Stephen Pinker does not

Belief and truth I I I

Belief is a relationship between a person and a proposition A person’s belief is their representation of how the world is Belief and truth are not the same thing I I

I

Not every true proposition is believed by any one person Probably every person believes some propositions which are false

Belief is relative to a person, but truth is not I

I I

Let p be the proposition that the earth is at most 10,000 years old Pat Buchanan believes p, but Stephen Pinker does not But, the truth of p depends only on the age of the earth,

Belief and truth I I I

Belief is a relationship between a person and a proposition A person’s belief is their representation of how the world is Belief and truth are not the same thing I I

I

Not every true proposition is believed by any one person Probably every person believes some propositions which are false

Belief is relative to a person, but truth is not I

I I

Let p be the proposition that the earth is at most 10,000 years old Pat Buchanan believes p, but Stephen Pinker does not But, the truth of p depends only on the age of the earth, I

and the age of the earth doesn’t even depend on whether any people ever existed,

Belief and truth I I I

Belief is a relationship between a person and a proposition A person’s belief is their representation of how the world is Belief and truth are not the same thing I I

I

Not every true proposition is believed by any one person Probably every person believes some propositions which are false

Belief is relative to a person, but truth is not I

I I

Let p be the proposition that the earth is at most 10,000 years old Pat Buchanan believes p, but Stephen Pinker does not But, the truth of p depends only on the age of the earth, I

I

and the age of the earth doesn’t even depend on whether any people ever existed, let alone on what people believe about it

What is the purpose of belief? I

But why believe anything?

What is the purpose of belief? I I

But why believe anything? What you should do generally depends on how things are

What is the purpose of belief? I I

But why believe anything? What you should do generally depends on how things are I

if it’s going to rain, then you should bring an umbrella

What is the purpose of belief? I I

But why believe anything? What you should do generally depends on how things are I I

if it’s going to rain, then you should bring an umbrella i.e., most imperatives are “hypothetical”

What is the purpose of belief? I I

But why believe anything? What you should do generally depends on how things are I I

I

if it’s going to rain, then you should bring an umbrella i.e., most imperatives are “hypothetical”

But what people actually do depends on how they think things are

What is the purpose of belief? I I

But why believe anything? What you should do generally depends on how things are I I

I

if it’s going to rain, then you should bring an umbrella i.e., most imperatives are “hypothetical”

But what people actually do depends on how they think things are I

Suppose Lisa believes it’s going to rain, but Lucy doesn’t.

What is the purpose of belief? I I

But why believe anything? What you should do generally depends on how things are I I

I

if it’s going to rain, then you should bring an umbrella i.e., most imperatives are “hypothetical”

But what people actually do depends on how they think things are I I

Suppose Lisa believes it’s going to rain, but Lucy doesn’t. Then Lisa will bring an umbrella but Lucy won’t

What is the purpose of belief? I I

But why believe anything? What you should do generally depends on how things are I I

I

But what people actually do depends on how they think things are I I

I

if it’s going to rain, then you should bring an umbrella i.e., most imperatives are “hypothetical”

Suppose Lisa believes it’s going to rain, but Lucy doesn’t. Then Lisa will bring an umbrella but Lucy won’t

If you didn’t believe anything, you wouldn’t know what to do

What is the purpose of belief? I I

But why believe anything? What you should do generally depends on how things are I I

I

But what people actually do depends on how they think things are I I

I I

if it’s going to rain, then you should bring an umbrella i.e., most imperatives are “hypothetical”

Suppose Lisa believes it’s going to rain, but Lucy doesn’t. Then Lisa will bring an umbrella but Lucy won’t

If you didn’t believe anything, you wouldn’t know what to do So beliefs guide action:

What is the purpose of belief? I I

But why believe anything? What you should do generally depends on how things are I I

I

But what people actually do depends on how they think things are I I

I I

if it’s going to rain, then you should bring an umbrella i.e., most imperatives are “hypothetical”

Suppose Lisa believes it’s going to rain, but Lucy doesn’t. Then Lisa will bring an umbrella but Lucy won’t

If you didn’t believe anything, you wouldn’t know what to do So beliefs guide action: I

If somebody believes that p, then she does what would be best if p

Belief and truth, 2

I

It is generally thought that false beliefs are defective

Belief and truth, 2

I I

It is generally thought that false beliefs are defective Thus, you should try only to believe what is true

Belief and truth, 2

I I I

It is generally thought that false beliefs are defective Thus, you should try only to believe what is true But why?

Belief and truth, 2

I I I I

It is generally thought that false beliefs are defective Thus, you should try only to believe what is true But why? One reason is that beliefs guide action:

Belief and truth, 2

I I I I

It is generally thought that false beliefs are defective Thus, you should try only to believe what is true But why? One reason is that beliefs guide action: I

If you believe that p, then you do what would be best if p

Belief and truth, 2

I I I I

It is generally thought that false beliefs are defective Thus, you should try only to believe what is true But why? One reason is that beliefs guide action: I I

If you believe that p, then you do what would be best if p But if p is false, then what would be best if p may not be what is best in fact

Belief and truth, 2

I I I I

It is generally thought that false beliefs are defective Thus, you should try only to believe what is true But why? One reason is that beliefs guide action: I I

I

If you believe that p, then you do what would be best if p But if p is false, then what would be best if p may not be what is best in fact So if you believe what is false, then you may not do what is best

Belief and truth, 2

I I I I

It is generally thought that false beliefs are defective Thus, you should try only to believe what is true But why? One reason is that beliefs guide action: I I

I

I

If you believe that p, then you do what would be best if p But if p is false, then what would be best if p may not be what is best in fact So if you believe what is false, then you may not do what is best

In other words, false beliefs have bad consequences

A consequentialist evaluation of belief

I

Consequentialism says: it is right to do A if doing A has the best consequences

A consequentialist evaluation of belief

I I

Consequentialism says: it is right to do A if doing A has the best consequences Applied to belief we get this:

A consequentialist evaluation of belief

I I

Consequentialism says: it is right to do A if doing A has the best consequences Applied to belief we get this: 1. it is right to believe p if believing p has the best consequences

A consequentialist evaluation of belief

I I

Consequentialism says: it is right to do A if doing A has the best consequences Applied to belief we get this: 1. it is right to believe p if believing p has the best consequences 2. believing what is true generally has better consequences than believing whta is false

A consequentialist evaluation of belief

I I

Consequentialism says: it is right to do A if doing A has the best consequences Applied to belief we get this: 1. it is right to believe p if believing p has the best consequences 2. believing what is true generally has better consequences than believing whta is false 3. So, it is generally right to believe what is true

Objections to belief-consequentialism, 1

I

Consequentialism doesn’t support rules of conduct

Objections to belief-consequentialism, 1

I I

Consequentialism doesn’t support rules of conduct Any interesting rule will have cases in which breaking it has better consequences

Objections to belief-consequentialism, 1

I I I

Consequentialism doesn’t support rules of conduct Any interesting rule will have cases in which breaking it has better consequences Specifically, believing a falsehood may sometimes have better consequences

Objections to belief-consequentialism, 1

I I I

Consequentialism doesn’t support rules of conduct Any interesting rule will have cases in which breaking it has better consequences Specifically, believing a falsehood may sometimes have better consequences I

E.g., suppose Lucy and Lisa are meeting for coffee

Objections to belief-consequentialism, 1

I I I

Consequentialism doesn’t support rules of conduct Any interesting rule will have cases in which breaking it has better consequences Specifically, believing a falsehood may sometimes have better consequences I I

E.g., suppose Lucy and Lisa are meeting for coffee If Lucy is an hour late, then it’s better for Lisa to have remembered the wrong time

Objections to belief-consequentialism, 1

I I I

Consequentialism doesn’t support rules of conduct Any interesting rule will have cases in which breaking it has better consequences Specifically, believing a falsehood may sometimes have better consequences I I

I

E.g., suppose Lucy and Lisa are meeting for coffee If Lucy is an hour late, then it’s better for Lisa to have remembered the wrong time But aren’t false beliefs defective no matter what?

Objections to belief-consequentialism, 2

I

Consequentialism is a theory of right action

Objections to belief-consequentialism, 2

I

Consequentialism is a theory of right action I

To decide what to do, you figure out what has the best consequences

Objections to belief-consequentialism, 2

I

Consequentialism is a theory of right action I

I

To decide what to do, you figure out what has the best consequences

So consequentialism applies to your choices

Objections to belief-consequentialism, 2

I

Consequentialism is a theory of right action I

I I

To decide what to do, you figure out what has the best consequences

So consequentialism applies to your choices But are beliefs chosen?

Objections to belief-consequentialism, 2

I

Consequentialism is a theory of right action I

I I

To decide what to do, you figure out what has the best consequences

So consequentialism applies to your choices But are beliefs chosen? I

Can you now decide to believe that it’s raining?

Objections to belief-consequentialism, 2

I

Consequentialism is a theory of right action I

I I

To decide what to do, you figure out what has the best consequences

So consequentialism applies to your choices But are beliefs chosen? I I

Can you now decide to believe that it’s raining? Seems crazy!

Origins of belief

I

You don’t start out believing everything you believe eventually

Origins of belief

I

You don’t start out believing everything you believe eventually I

E.g., six months ago you didn’t think your philosophy class would be in SHA 110

Origins of belief

I

You don’t start out believing everything you believe eventually I

I

E.g., six months ago you didn’t think your philosophy class would be in SHA 110 Rather, at some point you needed to get to class, so you needed to know where it is

Origins of belief

I

You don’t start out believing everything you believe eventually I

I

I

E.g., six months ago you didn’t think your philosophy class would be in SHA 110 Rather, at some point you needed to get to class, so you needed to know where it is

So how do beliefs arise?

Origins of belief

I

You don’t start out believing everything you believe eventually I

I

I I

E.g., six months ago you didn’t think your philosophy class would be in SHA 110 Rather, at some point you needed to get to class, so you needed to know where it is

So how do beliefs arise? Normally, belief that p arises from evidence that p

Origins of belief

I

You don’t start out believing everything you believe eventually I

I

I I

E.g., six months ago you didn’t think your philosophy class would be in SHA 110 Rather, at some point you needed to get to class, so you needed to know where it is

So how do beliefs arise? Normally, belief that p arises from evidence that p I

e.g., somebody believe’s its raining because they see water falling from the sky

Origins of belief

I

You don’t start out believing everything you believe eventually I

I

I I

So how do beliefs arise? Normally, belief that p arises from evidence that p I

I

E.g., six months ago you didn’t think your philosophy class would be in SHA 110 Rather, at some point you needed to get to class, so you needed to know where it is

e.g., somebody believe’s its raining because they see water falling from the sky

The question which beliefs are beneficial doesn’t come up

William James: The will to believe

I

James is a psychologist

William James: The will to believe

I I

James is a psychologist He knows that people’s beliefs do not just depend on their evidence

William James: The will to believe

I I

James is a psychologist He knows that people’s beliefs do not just depend on their evidence I

Rather, belief depends on desire, friendship, culture, etc.

William James: The will to believe

I I

James is a psychologist He knows that people’s beliefs do not just depend on their evidence I

I

Rather, belief depends on desire, friendship, culture, etc.

However: he argues that this is as it should be:

William James: The will to believe

I I

James is a psychologist He knows that people’s beliefs do not just depend on their evidence I

I

Rather, belief depends on desire, friendship, culture, etc.

However: he argues that this is as it should be: I

I.e., when answering a question you ought not only rely on evidence

Options

I

An option is a decision between two states of belief

Options

I I

An option is a decision between two states of belief An option is

Options

I I

An option is a decision between two states of belief An option is I

live, if the correctness of the beliefs is not settled

Options

I I

An option is a decision between two states of belief An option is I I

live, if the correctness of the beliefs is not settled forced, if you must choose one state over the other

Options

I I

An option is a decision between two states of belief An option is I I I

live, if the correctness of the beliefs is not settled forced, if you must choose one state over the other momentous, if what you choose matters a lot.

Options

I I

An option is a decision between two states of belief An option is I I I

I

live, if the correctness of the beliefs is not settled forced, if you must choose one state over the other momentous, if what you choose matters a lot.

An option is genuine if it is live, forced and momentous

Options

I I

An option is a decision between two states of belief An option is I I I

I I

live, if the correctness of the beliefs is not settled forced, if you must choose one state over the other momentous, if what you choose matters a lot.

An option is genuine if it is live, forced and momentous James contends that genuine options should not be decided only by evidence

Science

I

James argues that in science it is better to give in to your passions, if only tentatively:

Science

I

James argues that in science it is better to give in to your passions, if only tentatively: I

“The most useful investigator, because the most sensitive observer, is always he whose eager interest in one side of the question is balanced by an equally keen nervousness lest he become deceived.”

Science

I

James argues that in science it is better to give in to your passions, if only tentatively: I

I

“The most useful investigator, because the most sensitive observer, is always he whose eager interest in one side of the question is balanced by an equally keen nervousness lest he become deceived.” “Science has organized this nervousness into a regular technique, her so-called method of verification.”

Morality

I

Morality is about what is good.

Morality

I I

Morality is about what is good. Science can’t settle these, because it presupposes something about the good, namely that knowledge is good.

Morality

I I I

Morality is about what is good. Science can’t settle these, because it presupposes something about the good, namely that knowledge is good. Ayway, it’s not clear that there is truth or falsehood about morality, but if there is, then here our opinions must be decided by passion

Relationships

I

How about beliefs about people?

Relationships

I I

How about beliefs about people? Friendship requires unfounded belief in its existence

Relationships

I I

How about beliefs about people? Friendship requires unfounded belief in its existence I

Whether Lucy likes Robert depends on whether she believes Robert likes her

Relationships

I I

How about beliefs about people? Friendship requires unfounded belief in its existence I

I

Whether Lucy likes Robert depends on whether she believes Robert likes her Whether Robert likes Lucy depends on whether he believes Lucy likes him

Relationships

I I

How about beliefs about people? Friendship requires unfounded belief in its existence I

I

I

Whether Lucy likes Robert depends on whether she believes Robert likes her Whether Robert likes Lucy depends on whether he believes Lucy likes him

Cooperation requires belief in the faithfulness of the parties

Relationships

I I

How about beliefs about people? Friendship requires unfounded belief in its existence I

I

I I

Whether Lucy likes Robert depends on whether she believes Robert likes her Whether Robert likes Lucy depends on whether he believes Lucy likes him

Cooperation requires belief in the faithfulness of the parties Sometimes, the existence of a fact depends on belief in its existence

Relationships

I I

How about beliefs about people? Friendship requires unfounded belief in its existence I

I

I I

Whether Lucy likes Robert depends on whether she believes Robert likes her Whether Robert likes Lucy depends on whether he believes Lucy likes him

Cooperation requires belief in the faithfulness of the parties Sometimes, the existence of a fact depends on belief in its existence I

So we’d better believe it exists if we want it to be true

Relationships

I I

How about beliefs about people? Friendship requires unfounded belief in its existence I

I

I I

Whether Lucy likes Robert depends on whether she believes Robert likes her Whether Robert likes Lucy depends on whether he believes Lucy likes him

Cooperation requires belief in the faithfulness of the parties Sometimes, the existence of a fact depends on belief in its existence I I

So we’d better believe it exists if we want it to be true i.e., desire for p is sometimes a reason to believe that p

Dekalog 2

I

Dorota’s husband is mortally ill, and

Dekalog 2

I I

Dorota’s husband is mortally ill, and She is pregnant with another man’s child

Dekalog 2

I I I

Dorota’s husband is mortally ill, and She is pregnant with another man’s child She loves both men

Dekalog 2

I I I I

Dorota’s husband is mortally ill, and She is pregnant with another man’s child She loves both men She resolves:

Dekalog 2

I I I I

Dorota’s husband is mortally ill, and She is pregnant with another man’s child She loves both men She resolves: I

to have an abortion if her husband is going to live

Dekalog 2

I I I I

Dorota’s husband is mortally ill, and She is pregnant with another man’s child She loves both men She resolves: I I

to have an abortion if her husband is going to live to keep the child if her husband is going to die

Dekalog 2

I I I I

Dorota’s husband is mortally ill, and She is pregnant with another man’s child She loves both men She resolves: I I I

to have an abortion if her husband is going to live to keep the child if her husband is going to die So, she wants to know what will happen to her husband

Dekalog 2

I I I I

Dorota’s husband is mortally ill, and She is pregnant with another man’s child She loves both men She resolves: I I I

I

to have an abortion if her husband is going to live to keep the child if her husband is going to die So, she wants to know what will happen to her husband

How should Dorota decide what to believe?