PhB Bachelor of Philosophy Logic and Argumentation 1 — Questions and Answers
Question 1: A deductively valid argument is one in which:
- The premises are all true
- If the premises are true, the conclusion must be true (Correct answer)
- The conclusion is probably true given the premises
- The premises and conclusion are all well-established facts
Correct answer: If the premises are true, the conclusion must be true
Validity is a structural property: a valid argument cannot have true premises and a false conclusion—the conclusion is guaranteed by the premises.
Question 2: A sound argument is one that is:
- Valid and persuasive
- Valid and has all true premises (Correct answer)
- Invalid but has a true conclusion
- Inductively strong and well-supported
Correct answer: Valid and has all true premises
Soundness combines validity (correct logical form) with truth (all premises are actually true), guaranteeing a true conclusion.
Question 3: The fallacy of affirming the consequent is committed when someone argues:
- If P then Q; P; therefore Q
- If P then Q; Q; therefore P (Correct answer)
- If P then Q; not Q; therefore not P
- If P then Q; not P; therefore not Q
Correct answer: If P then Q; Q; therefore P
Affirming the consequent ('If P then Q; Q; therefore P') is invalid because Q may be true for reasons unrelated to P.
Question 4: Modus ponens is the valid argument form:
- If P then Q; not Q; therefore not P
- If P then Q; P; therefore Q (Correct answer)
- If P then Q; not P; therefore not Q
- If P then Q; Q; therefore P
Correct answer: If P then Q; P; therefore Q
Modus ponens ('mode of putting') is the foundational deductive rule: given the conditional and its antecedent, we validly infer the consequent.
Question 5: An ad hominem fallacy occurs when:
- An argument appeals to popular opinion
- An argument attacks the person making a claim rather than addressing the claim itself (Correct answer)
- A conclusion does not follow from the premises
- An argument uses emotionally loaded language
Correct answer: An argument attacks the person making a claim rather than addressing the claim itself
Ad hominem ('against the person') dismisses an argument by attacking the character or motives of the arguer rather than the argument's content.
Question 6: The straw man fallacy involves:
- Appealing to an authority who is not an expert in the relevant field
- Misrepresenting an opponent's argument to make it easier to refute (Correct answer)
- Claiming that two extreme positions are the only options
- Drawing a conclusion that goes beyond what the evidence supports
Correct answer: Misrepresenting an opponent's argument to make it easier to refute
A straw man replaces the actual argument with a distorted, weaker version, then attacks that—leaving the real argument unaddressed.
PhB Bachelor of Philosophy Logic and Argumentation 1
A deductively valid argument is one in which: