4. Exercises on identification and Evaluation

4.  Exercises on induction, deduction, and argument evaluation.

Identify the conclusion first. Then determine which pattern of argument the example fits best, to decide (confirm) that it is inductive or deductive.   To evaluate, first ask yourself if the conclusion follows from the premise(s), and after that, ask yourself if the premises are true.

 

  1. Humpty Dumpty is an egg, and he’s rude and bad at math, so some talking eggs are rude.

2. Humpty Dumpty is rude and bad at math, so all talking eggs are bad at math.

 

3. This Logic class meets in Trinkle, so all Logic classes meet in this building.

4.  The Republican nominee for President is going to be a woman, since Bachman, Romney, Paul, Perry, Gingrich, Santorum all are female.

 

5.  Gingrich must visit UMW often, since his campaign headquarters is in Westmoreland Hall.

6.  Romney and Gingrich both eat in Seacobeck once a month, and they both have grey hair, so Romney is probably overweight too, since Gingrich is.

 

7. The OWS people will probably vote for Romney because he’s a member of that top 1% they are always talking about.

8.  Alice can’t find her keys, so either she misplaced them or someone stole them.

 

9.  They can’t be stolen unless someone else came into the house after she unlocked the door, and no one did, so she must have misplaced them.

 

10. They must be around here somewhere, even if she still can’t find them, since no one stole them and she had them with her when she came in.

 

 

11. This January 1 was the 149th  anniversary of the Emancipation Proclamation. Lincoln must have signed it in 1863.

 

12. May is the best month in the whole world. One reason is because it’s my birthday. Another reason is because of spring. The third reason it’s the best month is because my friends and I go outside and play football.

 

 

13. The best month is December because my granddad says so, and he’s old.

 

14. CVS never closes. Their sign says “Open 24 hours.”

 

 

15. You need to slow down. That sign says 55 and you’re doing 70.

 

16. All the Congressmen running for POTUS say you can’t trust the government, so you really can’t.

 

 

17. Free public education, Social Security retirement benefits, and Medicaid are all examples of socialist thinking, so it can’t be all bad, since everyone agrees these are good things.

 

18. The recipe says to only use water, flour, salt and yeast. Your baguettes will come out better if you do that.

 

 

19. The last time I made bread, I used more yeast than just one tablespoon, and it came out great, so I’m going to try that again this time.

 

20. “Redskins” is kind of a racist name for a professional team, and they’ve had a terrible year too. They should change their name, and maybe they’ll do better next year.

 

 

21. The morning star is the same planet as the evening star, so “the morning star” means the same thing as “the evening star.”

 

22. Logic is part of philosophy, and Mary is a logician, so she’s got to be a philosopher.

 

 

23. Socrates was a philosopher, and he died. Plato died too.  Same thing with Aristotle.  And –all of them were men.  Lucius Outlaw is a man and a philosopher, so he’ll probably die too.

 

24. Socrates was a philosopher, and he died. Plato died too.  Same thing with Aristotle. Probably all philosophers die.

 

 

25. Socrates was a philosopher, and he died. Plato died too.  Same thing with Aristotle.  Not a good career choice.

 

26. Someone once said “Socrates is a man, all men are mortal, so Socrates is mortal.” This was a very wise man, so Socrates must have been mortal.

 

 

27. Socrates is a man, all men are mortal, so Socrates is mortal.

 

28. If someone’s a philosopher, he’s not going to live forever, because if you’re a philosopher, you’re mortal.

 

 

29. Either you’re a philosopher or you’re immortal. But no one’s immortal, so everyone’s a philosopher.

30.  Dr. Watson has been playing billiards, since he has chalk on his fingers.

31.   If I hadn’t paid, you wouldn’t be arguing with me,  but you are. So I did.

 

 

 

 

Answers

 

  1. Humpty Dumpty is an egg, and he’s rude and bad at math, so some talking eggs are rude.      Categorical Syllogism.  Valid.  Unsound.

2.  Humpty Dumpty is rude and bad at math, so all talking eggs are bad at math.   Generalization.   Weak (based on just a single example). Uncogent (because weak)

 

3.  This Logic class meets in Trinkle, so all Logic classes meet in this building.  Generalization.  Weak, uncogent.  But note that the conclusion is, in fact, true.

4.  The Republican nominee for President is going to be a woman, since Bachman, Romney, Paul, Perry, Gingrich, Santorum all are female.   Prediction. Strong (conclusion is likely. given the premise).  Uncogent (because the premise is, in fact, false).

 

5.  Gingrich must visit UMW often, since his campaign headquarters is in Westmoreland Hall.        Categorical syllogism (with a missing, implied premise: candidates visit their campaign headquarters often.)    Valid, unsound.

6.  Romney and Gingrich both eat in Seacobeck once a month, and they both have grey hair, so Romney is probably overweight too, since Gingrich is.   Analogy.  Weak.

 

7.  The OWS people will probably vote for Romney because he’s a member of that top 1% they are always talking about.     Prediction.  Weak.

8.  Alice can’t find her keys, so either she misplaced them or someone stole them.  Prediction. Strong.   (not “definition” since other possibilities include –someone taking them by mistake, her dog sitting on them, etc.).    Fictional example, so we cannot pronounce on cogency.       Not “disjunctive syllogism,” despite the existence of an “either…or” statement, because the “either…or” statement is the conclusion; the argument does not turn on the “either…or.”

 

9.  They can’t be stolen unless someone else came into the house after she unlocked the door, and no one did, so she must have misplaced them.

Disjunctive syllogism. Valid.    (“Unless” is another way to say “or.”)

 

10. They must be around here somewhere, even if she still can’t find them, since no one stole them and she had them with her when she came in.

 

Causal? But this seems more certain than “highly probable.”   For a deductive pattern, “by definition” could work: “Not elsewhere” means “here somewhere.”   Valid.

 

 

11. This January 1 was the 149 anniversary of the Emancipation Proclamation. Lincoln must have signed it in 1863.

From Math.  Valid. Sound

 

12. May is the best month in the whole world. One reason is because it’s my birthday. Another reason is because of spring. The third reason it’s the best month is because my friends and I go outside and play football.

 

Causal, if we take it as an argument.  No more weak than strong, since this is really just an explanation of why this third grader likes May the best.

 

 

13. The best month is December because my granddad says so, and he’s old.

From Authority. Weak.

 

14. CVS never closes. Their sign says “Open 24 hours.”

From Signs. Strong. Cogent.

 

 

15. You need to slow down. That sign says 55 and you’re doing 70.

From Signs. Strong.

 

16. All the Congressmen running for POTUS say you can’t trust the government, so you really can’t.

From Authority.  Weak.

 

 

 

 

17. Free public education, Social Security retirement benefits, and Medicaid are all examples of socialist thinking, so it can’t be all bad, since everyone agrees these are good things.

Categorical syllogism.  Valid. Sound? –does everyone agree?

 

18. The recipe says to only use water, flour, salt and yeast. Your baguettes will come out better if you do that.

Prediction.  Strong.  Cogent.  (The “if…then” statement is the conclusion; the conclusion is  not derived from or based on an “if…then” statement, so this is not a hypothetical syllogism.

 

 

19. The last time I made bread, I used more yeast than just one tablespoon, and it came out great, so I’m going to try that again this time.

Not really an argument.  It’s  not pertinent to try to convince us that he’s departing from the recipe; this offers an explanation of why he’s departing from the recipe.

 

20. “Redskins” is kind of a racist name for a professional team, and they’ve had a terrible year too. They should change their name, and maybe they’ll do better next year.   

Causal.  Weak (suggests that the name has a causal role in their record of success).

 

 

21. The morning star is the same planet as the evening star, so “the morning star” means the same thing as “the evening star.”

From Definition (of “meaning”). Invalid.

 

22. Logic is part of philosophy, and Mary is a logician, so she’s got to be a philosopher.

Categorical syllogism.  Valid.

 

 

23. Socrates was a philosopher, and he died. Plato died too.  Same thing with Aristotle.  And –all of them were men.  Lucius Outlaw is a man and a philosopher, so he’ll probably die too.    Analogy.  Strong. Cogent.

 

24. Socrates was a philosopher, and he died. Plato died too.  Same thing with Aristotle. Probably all philosophers die.       Generalization.   Weak (these are unusual philosophers?)

 

 

25. Socrates was a philosopher, and he died. Plato died too.  Same thing with Aristotle.  Not a good career choice.

Causal.  Weak (nothing here indicates that being a philosopher caused death).

 

26. Someone once said “Socrates is a man, all men are mortal, so Socrates is mortal.” This was a very wise man, so Socrates must have been mortal.

From Authority.  Weak (unnamed source).

 

 

27. Socrates is a man, all men are mortal, so Socrates is mortal.

Categorical Syllogism.  Valid. Sound.

 

28. If someone’s a philosopher, he’s not going to live forever, because if you’re a philosopher, you’re mortal.      Hypothetical syllogism?  Argument from definition?   (You can see it paraphrases the Categorical syllogism.)   Valid.  Sound.

 

29. Either you’re a philosopher or you’re immortal. But no one’s immortal, so everyone’s a philosopher.

Disjunctive syllogism.  Valid.  Unsound (the premise is a false dichotomy).

 

30. Dr. Watson has been playing billiards, since he has chalk on his fingers.

Causal.  Strong.

 

31. If I hadn’t paid, you wouldn’t be arguing with me,  but you are. So I did.

Hypothetical syllogism (actually we’ll call it Modus Tollens in a few weeks).   Valid.

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