Logic
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Transcript of Logic
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
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
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.
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.
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.
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.
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.
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)
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