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Logic: Language and Informatio

1-1-1 Propositions

Greg Restall

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What isLogicall about?

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What isLogicall about?

One answer Propositions, and

relationships between them.

consistency

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What isLogicall about?

One answer Propositions, and

relationships between them.

consistency

consequence

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What isLogicall about?

One answer Propositions, and

relationships between them.

consistency

consequence

equivalence

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Example Propositions

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Example Propositions

A sentence expresses a propositionif it makes some statement

about how things are.

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Example Propositions

A sentence expresses a propositionif it makes some statement

about how things are.

We have students from all over the world.

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Example Propositions

A sentence expresses a propositionif it makes some statement

about how things are.

We have students from all over the world.

There is no difference between the mind and the brain.

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Example Propositions

A sentence expresses a propositionif it makes some statement

about how things are.

We have students from all over the world.

There is no difference between the mind and the brain.

3+ 5 < 4+ 3.

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Example Non-Propositions

Not all sentences express propositions.

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Example Non-Propositions

Not all sentences express propositions.

Please dont watch these lectures while driving a car.

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Example Non-Propositions

Not all sentences express propositions.

Please dont watch these lectures while driving a car.

What is the capital of Ethiopia?

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Example Non-Propositions

Not all sentences express propositions.

Please dont watch these lectures while driving a car.

What is the capital of Ethiopia?

Thank goodness; the poor cat!

l

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Example Non-Propositions

Not all sentences express propositions.

Please dont watch these lectures while driving a car.

What is the capital of Ethiopia?

Thank goodness; the poor cat!

Hi, Jen!

H d ll hi h i i

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How do we tell which sentences express propositio

Here are guidelines for distinguishing sentences that expresspropositions from those that dont:

H d ll hi h i i

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How do we tell which sentences express propositio

Here are guidelines for distinguishing sentences that expresspropositions from those that dont:

A propositionis the kind of thing you could:

H d ll hi h i i

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How do we tell which sentences express propositio

Here are guidelines for distinguishing sentences that expresspropositions from those that dont:

A propositionis the kind of thing you could:

believeordisbelieve;

H d t ll hi h t iti

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How do we tell which sentences express propositio

Here are guidelines for distinguishing sentences that expresspropositions from those that dont:

A propositionis the kind of thing you could:

believeordisbelieve;

agreeordisagreewith;

H d t ll hi h t iti

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How do we tell which sentences express propositio

Here are guidelines for distinguishing sentences that expresspropositions from those that dont:

A propositionis the kind of thing you could:

believeordisbelieve;

agreeordisagreewith;

assertordeny;

How do we tell which sentences express propositio

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How do we tell which sentences express propositio

Here are guidelines for distinguishing sentences that expresspropositions from those that dont:

A propositionis the kind of thing you could:

believeordisbelieve;

agreeordisagreewith;

assertordeny;

give a reasonfororagainst;

How do we tell which sentences express propositio

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How do we tell which sentences express propositio

Here are guidelines for distinguishing sentences that expresspropositions from those that dont:

A propositionis the kind of thing you could:

believeordisbelieve;

agreeordisagreewith;

assertordeny;

give a reasonfororagainst;

use as a reasonfororagainstsomething else; and

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Exercise

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Exercise

Exercise

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Exercise

Which of these sentences express propositions?

Greg lives in Melbourne.

What do you think of logic so far?

I wish I had learned logic before!

Its immoral to consume meat.

This last sentence on the list is not true.

Next Up: Connectives and Combining Propositio

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Next Up: Connectives and Combining Propositio