Lecture 5

Question 1

What are the valid Argument forms?

Answer 1

• Argument by Elimination
  1. either P or Q
  2. Not P
  3. Therefore Q

Simplification
1. P and Q
2. Therefore P

Modus Ponens
1. If P then Q
2. P
3. Therefore Q

Modus Tollens
1. if P then Q
2. Not Q
3. Therefore not P

Chain arugment
1. if P and q
2. if Q then R
3. Therefore if P then R

Equivalence
1. P if and only if Q
2. Not P
3. Therefore Not Q

Question 2

What are the invalid argument forms

Answer 2

Affirming the Consequent
1. If P then Q
2. Q
3. Therefore P

Denying the antecedent
1. if P then Q
2. Not P
3. Therefore Not Q

Question 3

What is the finding vaildity and invaildty tip 1

Answer 3

Tip 1: Find examples to establish invaildity ( Counter examples)

Question 4

what is the finding vaildity and invaildity tip 2

Answer 4

Tip 2: Look for arguments that follow the same pattern, where validity or invalidity might be easier to idenifty.

Question 5

Finding Validity and Invalidity Tip3

Answer 5

Check the pattern
- see if it fits within one of the patterns we learned

Question 6

Two kind of validity

Answer 6

Semantic: Valid because it follows a valid argument form

Modal: Valid because of the meaning of terms
EXAMPLE: 1.
1. if it rains, the ground will be wet
2. it rains
3. Therefore the ground is wet