Chapter 4: Entailment Flashcards
Entailment
when the truth of premises absolutely guarantees the truth of the conclusion
Deductive validity
premises actually entailing conclusions
Deductive argument
premises presented as entailing conclusion
Deductively Valid (Suppositional Strength)
good suppositional strength does not amount to deductive validity
Deductively Valid Cases
For deductive validity, there can be no possible situation in which premises are true and conclusion false
Flipping the Argument
Evaluating an argument by starting with the conclusion
Assumes conclusion is false
Disjunction
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
Counterexamples
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
Reasons For Overlooking Entailment:
- using logical form as sole measure of entailment
- forgetting that false premises can still entail conclusion
- overly complex argument