Logic 101 Practice Problems (Set 1)

1. Identifying Arguments

Determine whether each passage contains an argument. If it does, identify the premises and the conclusion.

1. “Because the streets are wet, it must have rained last night.”

2. “Close the door right now!”

3. “Most cats purr when they’re happy. My cat is purring, so she’s probably happy.”

4. “I’ll meet you at 5.”

5. “Everyone at the debate tournament is wearing a badge, so Alex must be wearing a badge too.”

2. Premise & Conclusion Indicators

Identify the indicator words and identify whether they signal a premise or conclusion.

1. “Since debate requires preparation, you should always research before a round.”

2. “You dropped your arguments; therefore, you lost the round.”

3. “You can infer from the evidence that the witness is lying.”

4. “Because Alex is the best speaker, the team should let him give the final rebuttal.”

5. “It follows that if practice improves performance, then skipping practice hurts performance.”

3. Validity Check

For each argument, decide if it is valid or invalid. (Don’t worry about whether the premises are true.)

1. All dogs are animals.

2. All poodles are dogs.

3. Therefore, all poodles are animals.

1. If it’s raining, then the ground is wet.

2. The ground is wet.

3. Therefore, it’s raining.

1. The moon is made of cheese.

2. Cheese is delicious.

3. Therefore, the moon is delicious.

1. All debaters love logic.

2. Maria is a debater.

3. Therefore, Maria loves logic.

4. Soundness Check

Say whether each argument is sound or unsound.

1. If water boils at 212°F, then you can make tea by heating water.

2. Water boils at 212°F.

3. Therefore, you can make tea by heating water.

1. If unicorns exist, then they are mammals.

2. Unicorns exist.

3. Therefore, unicorns are mammals.

5. Deductive or Inductive?

Classify each argument as deductive or inductive.

1. “If all humans are mortal, and Socrates is human, then Socrates is mortal.”

2. “Most students at this tournament are tired. Jamie is a student at this tournament. So, Jamie is probably tired.”

3. “If I don’t practice my speech, I will do poorly. I didn’t practice. Therefore, I will do poorly.”

4. “Every time I’ve eaten at that restaurant, the food was good. So the next meal will probably be good too.”

6. Construct Your Own

• Write one valid but unsound argument.

• Write one sound argument.

• Write one inductive argument about debate tournaments.