Fallacious reasoning

Each of the following examples contains or suggests an argument that contains an informal fallacy. For each argument, identify the fallacy and state why the conclusion does not follow from the premises.

1. There are cases in which capital punishment is morally justified. Even Abraham Lincoln declined to pardon a young soldier who had been condemned to death for desertion.

2. The Supreme Court has ruled that persons accused of crimes cannot be interrogated unless their lawyer is present. I think this shows more concern for the criminal than for the victim. Laws exist to protect law-abiding citizens, not criminals. The police have a duty to get the facts, and one way to do that is to question the criminal. The Supreme Court's ruling is simply wrong.

3. The idea of treating frostbite by putting snow on it is absurd. It is one of the many folk remedies that originated among poor and ignorant people who had no access to competent medical help.

4. Each autumn, as soon as the frost comes, the leaves begin to turn. Some years, when the first frost is very severe, the leaves seem to turn almost overnight, and the entire countryside explodes in glorious hues of crimson and gold.

5. Professor: ‘Your assignment for next week is as follows. First, read the three essays handed out in class. Second, write a brief summary of each. Third, identify the one you liked least well. Fourth, write an essay describing the defect in your character to which you attribute this dislike.'

6. Man to bank teller: ‘I'd like to cash a check.' Teller: ‘Do you have any identification?' Man: ‘Yes, my friend here will identify me.' Teller: ‘But I don't know your friend.' Man: ‘No problem. I'll introduce you.'

7. John Stuart Mill: "Each person's happiness is a good to that person, and the general happiness, therefore, a good to the aggregate of all persons."

8. Jesus said, "The poor ye always have with you." Thus it is obviously futile to attempt to eradicate poverty, since the Lord said that trying to do this is doomed to failure.

9. Laws against discrimination are ridiculous. We could not survive even for a moment without discrimination! We discriminate between foods we do and don't like, between music we do and don't like, between people we do and don't like--we can't live without it, and it is wrong to expect us to do so.

10. Chinese spokesperson: ‘Don't presume to lecture us about human rights. How do you treat minorities in your own country? What are you doing for Native Americans, or for African Americans? Put your own house in order before you tell us what to do!'

The following passages contain fallacies of relevance. Identify the fallacy.

11. The Golden Rule is basic to every system of ethics ever devised, and everyone accepts it in some form or other. It is, therefore, an undeniably sound moral principle.

12. No mathematician has ever been able to demonstrate the truth of the "last theorem" of Fermat. It is therefore false.

13. Of course there is a Santa Claus. But he doesn't bring any presents to children who don't believe in him.

14. Mr. Scrooge, I can hardly manage to feed my children on what you have been paying me. And my youngest child, Tim, needs an operation if he is ever to walk again. So I deserve a raise!

15. "Mysticism is one of the great forces of world history. For religion is nearly the most important thing in the world, and religion never remains for long untouched by mysticism." (J. McTaggart, Some Dogmas of Religion)

The following passages contain fallacies of ambiguity. Identify the fallacy.

16. "Seeing that the eye and the hand and foot and every one of our members has some obvious function, must we not believe in a like manner that a human being has a function over and above these particular functions?" (Aristotle, Nicomachean Ethics)

17. The Bach children were both numerous and musical.

18. Improbable events happen every day, but what happens every day is precisely what is very probable. Therefore improbable events are very probable events.

19. The Delphic Oracle said to Croesus, King of Lydia, when Croesus asked the oracle if he should attack the Persia and its King, Cyrus the Great: ‘If Croesus goes to war with Cyrus, he will destroy a mighty kingdom.'

20. Traditional definition of anthropology: ‘The science of man embracing woman.' The following fallacies are of different types. For each case, identify the fallacy.
21. Everything in the universe serves a function that goes beyond itself. So the universe itself must serve a function that goes beyond itself.

22. Isn't it true that all students who get A grades study hard? So if you want me to study hard, Professor, give me an A!

23. The President must be a good friend to the working people of this country, because he told them so last night, and no one would lie to his friends.

24. "If you're not part of the solution then you're part of the problem." (E. Cleaver)

25. Nothing is unthinkable. For to think of nothing is simply not to think at all.

Overview: In your experience, what role do informal fallacies play in everyday speech? Do people make logical mistakes frequently, or is this more of a rare thing that only happens occasionally? Have you ever caught yourself using poor reasoning? Is it important to reason correctly? -- is it OK sometimes to reason poorly? -- how does a person check herself or himself to make sure that you are thinking correctly about something?