6H Practice: Enthymemes - Missing premises and conclusions; Determining whether arguments are valid or invalid - Logic 5e Student Resources

1. Determine which one of the following conclusions makes this incomplete argument valid.

A broken cell phone will be replaced only if it is accompanied by a sales slip. I do not have the sales slip for my broken cell phone.

My broken cell phone will not be replaced.

My cell phone will not be replaced.

My broken cell phone will be replaced.

My cell phone will be replaced.

2. Determine which one of the following missing conclusions makes this incomplete argument valid.

Anyone who can successfully find their way home can learn logic. All the students in this class can successfully find their way home.

Most students in this class can learn logic.

All the students in this class can learn logic.

Not all students in this class can learn logic.

None of the students in this class can learn logic.

3. Determine which one of the following premises makes this incomplete argument valid.

A few state laws are unconstitutional. They will be overturned by the Supreme Court.

Most unconstitutional laws are laws overturned by the Supreme Court.

No unconstitutional laws are laws overturned by the Supreme Court.

All unconstitutional laws are laws overturned by the Supreme Court.

Not all unconstitutional laws are laws overturned by the Supreme Court.

4. Determine which one of the following missing premises makes this incomplete argument valid.

Some airline companies take their customers for granted, because any company that refuses to give a refund on a purchase takes their customers for granted.

Some airline companies refuse to give a refund on a purchase.

Some companies refuse to give a refund on a purchase.

Not all airline companies refuse to give a refund on a purchase.

Some airline companies give a refund on a purchase.

5. The following enthymeme was adapted from either a newspaper, a website, or another source. First, supply the missing premise or conclusion for the following enthymemes. Second, translate the results into standard-form categorical syllogisms. Third, test your answers by using Venn diagrams and the six rules under the modern interpretation.

The two Koreas are still technically at war—the Korean War ended only with a truce.
Peter Beck, “Obama and South Korea Leader Agree to Hold Joint Military Exercise,” MSNBC.com

Missing premise: All wars that ended only with a truce are countries still technically at war. Valid.

Missing conclusion: All wars that ended only with a truce are countries still technically at war. Valid.

Missing premise: All wars that ended only with a truce are countries still technically at war. Invalid.

Missing conclusion: All wars that ended only with a truce are countries still technically at war. Invalid.

6. The following enthymeme was adapted from either a newspaper, a website, or another source. First, supply the missing premise or conclusion for the following enthymemes. Second, translate the results into standard-form categorical syllogisms. Third, test your answers by using Venn diagrams and the six rules under the modern interpretation.

All of us failed to match our dreams of perfection. So I rate us on the basis of our splendid failure to do the impossible.
William Faulkner, Writers at Work, First Series, ed. Malcolm Cowley

Missing premise: All people with dreams of perfection are splendid failures to do the impossible. Valid.

Missing conclusion: All people with dreams of perfection are splendid failures to do the impossible. Valid.

Missing premise: All people with dreams of perfection are splendid failures to do the impossible. Invalid.

Missing conclusion: All people with dreams of perfection are splendid failures to do the impossible. Invalid.

7. Determine which one of the following missing conclusions makes this incomplete argument valid.

Several varsity sports teams have hazing rituals. Those that do will be suspended.

Some varsity sports teams will not be suspended.

Some varsity sports teams will be suspended.

All varsity sports teams will be suspended.

No varsity sports teams will be suspended.

8. Determine which one of the following missing premises makes this incomplete argument valid.

Every year Global greenhouse gas emissions’ rise is detrimental to Earth’s survival because every year more and more people eating meat is detrimental to Earth’s survival.

All years that more and more people eat meat are years when greenhouse gas emissions rise.

No years that more and more people eat meat are years when greenhouse gas emissions rise.

Some years that more and more people eat meat are years when greenhouse gas emissions rise.

Some years that more and more people eat meat are not years when greenhouse gas emissions rise.

9. Determine which one of the following missing conclusions makes this incomplete argument valid.

While it’s true that all smart people wear glasses, it’s definitely not the case that tall people wear glasses.

All smart people are tall.

No smart people are tall.

Some smart people are tall.

Some smart people are not tall.

10. Determine which one of the following missing premises makes this incomplete argument valid.

Not every dog likes swimming, so some dogs aren’t Labradors.

All Labradors are dogs that like swimming.

No Labradors are dogs that like swimming.

Some Labradors are dogs that like swimming.

Some Labradors are not dogs that like swimming.

11. Determine which one of the following missing premises makes this incomplete argument valid.

I know for a fact that there isn’t a single Olympian who uses performance-enhancing drugs because none of my friends use performance-enhancing drugs.

All Olympians are people who are my friends.

No Olympians are people who are my friends.

Some Olympians are people who are my friends.

Some Olympians are not people who are my friends.

12. Determine which one of the following missing premises makes this incomplete argument valid.

Some people aren’t polite because no one has manners anymore!

Some types of politeness require manners.

No types of politeness require manners.

Some types of politeness do not require manners.

All types of politeness require manners.

13. Determine which one of the following missing conclusions makes this incomplete argument valid.

All humans are mammals, but only a few humans are rational.

All rational beings are mammals.

Some rational beings are mammals.

No rational beings are mammals.

Some rational beings are not mammals.

14. Determine which one of the following missing premises makes this incomplete argument valid.

There isn’t a single reality TV show that is a high-quality program since no high-quality programs involve throwing tables.

All reality TV shows are programs that involve throwing tables.

No reality TV shows are programs that involve throwing tables.

Some reality TV shows are programs that involve throwing tables.

Some reality TV shows are not programs that involve throwing tables.

15. Determine which one of the following missing conclusions makes this incomplete argument valid.

All dogs are animals that bite, and no fish are animals that bite.

All dogs are fish.

No dogs are fish.

Some dogs are fish.

Some dogs are not fish.

6H Practice: Enthymemes - Missing premises and conclusions; Determining whether arguments are valid or invalid

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