PHIL 447N Complete Study Guide: 100 Practice Questions on Fallacies,
Deductive Logic, Categorical Syllogisms, Inductive Reasoning, and Cognitive
Biases with Expert Explanations
Section 1: Informal Fallacies
1. "If we allow students to retake exams, next they will want to rewrite essays,
then they will want to skip finals altogether. Soon, there will be no academic
standards left."
What fallacy is being committed?
A. Slippery Slope
B. Hasty Generalization
C. Ad Hominem
D. Straw Man
Answer: A. Slippery Slope
Explanation: The argument assumes that allowing a minor concession (retaking exams)
will inevitably lead to an extreme, undesirable outcome (no academic standards) without
providing evidence for the chain of events.
2. "Dr. Smith argues that we should increase funding for public health, but Dr.
Smith was recently divorced and has been acting erratically. We should ignore his
proposal."
What fallacy is being committed?
A. Ad Hominem (Circumstantial)
B. Appeal to Authority
C. Red Herring
D. Tu Quoque
Answer: A. Ad Hominem (Circumstantial)
Explanation: This attacks the person making the argument (their personal life/character)
rather than addressing the merits of the funding proposal.
,3. "Either we ban all cars from the city center, or we accept that pedestrians will
continue to be hit by vehicles."
What fallacy is being committed?
A. Begging the Question
B. False Dilemma
C. Appeal to Ignorance
D. Equivocation
Answer: B. False Dilemma
Explanation: This presents only two extreme options when there are many alternatives
(e.g., implementing traffic calming measures, creating designated bike lanes, speed
limits).
4. "My grandfather smoked two packs a day and lived to be 95. Therefore,
smoking is not harmful to your health."
What fallacy is being committed?
A. Hasty Generalization
B. Appeal to Probability
C. Anecdotal Fallacy
D. Post Hoc Ergo Propter Hoc
Answer: C. Anecdotal Fallacy
Explanation: The arguer uses a single personal story (anecdote) to dismiss statistical
evidence or general scientific consensus.
5. "You can’t prove that ghosts don’t exist, so they must exist."
What fallacy is being committed?
A. Burden of Proof
B. Appeal to Ignorance
C. Begging the Question
D. Composition
Answer: B. Appeal to Ignorance
Explanation: It argues that a proposition is true simply because it has not been proven
false.
,Section 2: Deductive Logic & Validity
6. If an argument is valid and has all true premises, it is:
A. Sound
B. Cogent
C. Strong
D. Weak
Answer: A. Sound
Explanation: In deductive logic, validity ensures the conclusion follows from the
premises; soundness adds the requirement that the premises are actually true.
7. Identify the argument form:
If it rains, the ground gets wet.
The ground is wet.
Therefore, it rained.
A. Modus Ponens
B. Modus Tollens
C. Affirming the Consequent
D. Denying the Antecedent
Answer: C. Affirming the Consequent
Explanation: This is a formal fallacy. The structure is: If P then Q; Q; therefore P. This is
invalid because the ground could be wet for other reasons (sprinklers, a hose).
8. Which of the following is a valid argument form?
A. If P then Q; Not P; Therefore Not Q
B. If P then Q; Not Q; Therefore Not P
C. All A are B; Some B are C; Therefore Some A are C
D. Most A are B; Most B are C; Therefore Most A are C
Answer: B. If P then Q; Not Q; Therefore Not P
Explanation: This is Modus Tollens, a valid form. (If A then B; Not B; so Not A).
, Section 3: Categorical Logic (Syllogisms)
9. Translate into standard form: "Only registered voters can vote."
A. All registered voters are people who can vote.
B. No non-registered voters are people who can vote.
C. All people who can vote are registered voters.
D. Some voters are registered.
Answer: C. All people who can vote are registered voters.
Explanation: "Only A is B" translates to "All B are A."
10. Evaluate the syllogism:
All philosophers are thinkers.
Some thinkers are logicians.
Therefore, some philosophers are logicians.
A. Valid
B. Invalid (Undistributed Middle)
C. Invalid (Illicit Major)
D. Sound
Answer: B. Invalid (Undistributed Middle)
Explanation: The middle term ("thinkers") is not distributed in either premise. Just
because philosophers are thinkers, and some thinkers are logicians, the philosophers
might not be the same thinkers who are logicians.
Section 4: Inductive Reasoning & Probability
11. "A survey of 100 college students at a private Ivy League university found that
80% support candidate X. Therefore, 80% of all Americans support candidate X."
What is the primary weakness?
A. Unrepresentative sample
B. Small sample size
Deductive Logic, Categorical Syllogisms, Inductive Reasoning, and Cognitive
Biases with Expert Explanations
Section 1: Informal Fallacies
1. "If we allow students to retake exams, next they will want to rewrite essays,
then they will want to skip finals altogether. Soon, there will be no academic
standards left."
What fallacy is being committed?
A. Slippery Slope
B. Hasty Generalization
C. Ad Hominem
D. Straw Man
Answer: A. Slippery Slope
Explanation: The argument assumes that allowing a minor concession (retaking exams)
will inevitably lead to an extreme, undesirable outcome (no academic standards) without
providing evidence for the chain of events.
2. "Dr. Smith argues that we should increase funding for public health, but Dr.
Smith was recently divorced and has been acting erratically. We should ignore his
proposal."
What fallacy is being committed?
A. Ad Hominem (Circumstantial)
B. Appeal to Authority
C. Red Herring
D. Tu Quoque
Answer: A. Ad Hominem (Circumstantial)
Explanation: This attacks the person making the argument (their personal life/character)
rather than addressing the merits of the funding proposal.
,3. "Either we ban all cars from the city center, or we accept that pedestrians will
continue to be hit by vehicles."
What fallacy is being committed?
A. Begging the Question
B. False Dilemma
C. Appeal to Ignorance
D. Equivocation
Answer: B. False Dilemma
Explanation: This presents only two extreme options when there are many alternatives
(e.g., implementing traffic calming measures, creating designated bike lanes, speed
limits).
4. "My grandfather smoked two packs a day and lived to be 95. Therefore,
smoking is not harmful to your health."
What fallacy is being committed?
A. Hasty Generalization
B. Appeal to Probability
C. Anecdotal Fallacy
D. Post Hoc Ergo Propter Hoc
Answer: C. Anecdotal Fallacy
Explanation: The arguer uses a single personal story (anecdote) to dismiss statistical
evidence or general scientific consensus.
5. "You can’t prove that ghosts don’t exist, so they must exist."
What fallacy is being committed?
A. Burden of Proof
B. Appeal to Ignorance
C. Begging the Question
D. Composition
Answer: B. Appeal to Ignorance
Explanation: It argues that a proposition is true simply because it has not been proven
false.
,Section 2: Deductive Logic & Validity
6. If an argument is valid and has all true premises, it is:
A. Sound
B. Cogent
C. Strong
D. Weak
Answer: A. Sound
Explanation: In deductive logic, validity ensures the conclusion follows from the
premises; soundness adds the requirement that the premises are actually true.
7. Identify the argument form:
If it rains, the ground gets wet.
The ground is wet.
Therefore, it rained.
A. Modus Ponens
B. Modus Tollens
C. Affirming the Consequent
D. Denying the Antecedent
Answer: C. Affirming the Consequent
Explanation: This is a formal fallacy. The structure is: If P then Q; Q; therefore P. This is
invalid because the ground could be wet for other reasons (sprinklers, a hose).
8. Which of the following is a valid argument form?
A. If P then Q; Not P; Therefore Not Q
B. If P then Q; Not Q; Therefore Not P
C. All A are B; Some B are C; Therefore Some A are C
D. Most A are B; Most B are C; Therefore Most A are C
Answer: B. If P then Q; Not Q; Therefore Not P
Explanation: This is Modus Tollens, a valid form. (If A then B; Not B; so Not A).
, Section 3: Categorical Logic (Syllogisms)
9. Translate into standard form: "Only registered voters can vote."
A. All registered voters are people who can vote.
B. No non-registered voters are people who can vote.
C. All people who can vote are registered voters.
D. Some voters are registered.
Answer: C. All people who can vote are registered voters.
Explanation: "Only A is B" translates to "All B are A."
10. Evaluate the syllogism:
All philosophers are thinkers.
Some thinkers are logicians.
Therefore, some philosophers are logicians.
A. Valid
B. Invalid (Undistributed Middle)
C. Invalid (Illicit Major)
D. Sound
Answer: B. Invalid (Undistributed Middle)
Explanation: The middle term ("thinkers") is not distributed in either premise. Just
because philosophers are thinkers, and some thinkers are logicians, the philosophers
might not be the same thinkers who are logicians.
Section 4: Inductive Reasoning & Probability
11. "A survey of 100 college students at a private Ivy League university found that
80% support candidate X. Therefore, 80% of all Americans support candidate X."
What is the primary weakness?
A. Unrepresentative sample
B. Small sample size
