Logic

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Logic The Lost Art of Argument

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Logic. The Lost Art of Argument. Logic - Review. Proposition – A statement that is either true or false (but not both) Conjunction – And Disjunction – Or Negation – Not Truth Tables can be used to determine Equivalence Equivalence – Two propositions have the same truth values. - PowerPoint PPT Presentation

Transcript of Logic

Page 1: Logic

Logic

The Lost Art of Argument

Page 2: Logic

Logic - Review

Proposition – A statement that is either true or false (but not both)

Conjunction – And

Disjunction – Or

Negation – Not

Truth Tables can be used to determine Equivalence

Equivalence – Two propositions have the same truth values

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Conditional Sentences

Definition: Conditional Sentence – Given two propositions P, Q.P QP implies QIf P, then Q

Examples:If it is raining, then the roof is wet.If I am late for class, then it is Monday.If you don’t wear your lucky shirt, then you will lose the game.If 4 is an even number, then 4 > 8If the moon is round, then the chair is blue

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Conditional Sentences

Definition: Antecedent – If P Q, then P is called the antecedent.

Definition: Consequent – If P Q, then Q is called the consequent.

Identify the Antecedent and Consequent in the following:

If it is raining, then the roof is wet.

If I am late for class, then it is Monday.

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Conditional Sentences

Definition: Negation – For propositions P and Q, the negation of P Q is ~P ~Q

Examples:

If it is raining, then the roof is wet.

Negation: If it is not raining, then the roof is not wet.

If I am late for class, then it is Monday.

Negation: If I am not late for class, then it is not Monday.

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Conditional Sentences

Definition: Converse – For propositions P and Q, the converse of P Q is Q P

Examples:

If it is raining, then the roof is wet.

Converse: If the roof is wet, then it is raining.

If I am late for class, then it is Monday.

Converse: If it is Monday, then I am late for class.

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Conditional Sentences

Definition: Contrapositive – For propositions P and Q, the contrapositive of P Q is (~Q) (~P)

Examples:

If it is raining, then the roof is wet.

Contrapositive: If the roof is not wet, then it is not raining.

If I am late for class, then it is Monday.

Contrapositive: If it is not Monday, then I am not late for class.

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Conditional Sentences

Transitive Property of Conditional Sentences: P Q, Q R, then P R

Examples:

If it is raining, then I am late for class.

If I am late for class, then it is Monday.

If it is raining, then it is Monday.

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Logic - Review

Definition: Conditional Sentence – Given two propositions P, Q.P QP implies QIf P, then Q

Definition: Antecedent – If P Q, then P is called the antecedent.Definition: Consequent – If P Q, then Q is called the consequent.

Definition: Negation – For propositions P and Q, the negation of P Q is ~P ~Q

Definition: Converse – For propositions P and Q, the converse of P Q is Q P

Definition: Contrapositive – For propositions P and Q, the contrapositive of P Q is (~Q) (~P)

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Logic – Next Time

Syllogisms

All the old articles in this cupboard are cracked

All jugs in this cupboard are old

Nothing in this cupboard that is cracked will hold water