Chapter 4: Entailment

Question 1

Entailment

Answer 1

when the truth of premises absolutely guarantees the truth of the conclusion

Question 2

Deductive validity

Answer 2

premises actually entailing conclusions

Question 3

Deductive argument

Answer 3

premises presented as entailing conclusion

Question 4

Deductively Valid (Suppositional Strength)

Answer 4

good suppositional strength does not amount to deductive validity

Question 5

Deductively Valid Cases

Answer 5

For deductive validity, there can be no possible situation in which premises are true and conclusion false

Question 6

Flipping the Argument

Answer 6

Evaluating an argument by starting with the conclusion

Assumes conclusion is false

Question 7

Disjunction

Answer 7

Sentence is true as long as either P or Q is true (or both are)

Sentence is false when both P and Q are false

Question 8

Counterexamples

Answer 8

Instance that proves a universal claim to be false

If a form is deductively valid, every instance is deductively valid

Finding an invalid instance is a counterexample to the universal claim

Question 9

Reasons For Overlooking Entailment:

Answer 9

1. using logical form as sole measure of entailment
2. forgetting that false premises can still entail conclusion
3. overly complex argument