lecture 9 - PHIL 102 Logic and Reasoning Test 1 Logic and...

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Unformatted text preview: 9/26/2011 PHIL 102 Logic and Reasoning Test 1 Logic and Reasoning PHIL 102 [9] Sept 26 RECAP In-class test 28 Sept (instead of lecture) Covers ch. 1 to ch. 5 • • • • • • PHIL 102 Logic and Reasoning Test 1 Format: • Part A: 10 multiple choice questions x 5 marks each = 50 marks • Note: only one answer is correct • Part B: 6 short answer questions x 2.5 marks each = 15 marks • Part C: 2 logical form question x 2.5 marks = 5 marks • Part D: 2 diagramming question x 7.5 marks = 15 marks • Part E: 1 reverse diagramming question x 15 marks = 15 marks 30% of total grade Covers chapters 1 to 5 Materials to prepare: lecture notes + textbook Date 28 Sept. Held in‐class, 45 min (12:00 – 12:45) Bring ID with you, a functional pen. If you miss(ed) the test, contact me asap. You will be allowed to sit the make‐up test only if the absence from this one can be documented. A. Multiple choice • Critical thinking concerns… a. Determining the cause of our beliefs b. Pinpointing the psychological basis of our beliefs c. Determining the quality of our beliefs d. Assessing the practical impact of our beliefs A. Multiple choice A. Multiple choice • A statement is… • Statements backed by good reasons are… a. A question or exclamation b. An affirmation of prior beliefs c. An assertion that something is or is not the case d. An assertion that is neither true nor false a. b. c. d. To be believed with certainty Worthy of strong acceptance Beyond doubt Deserving of weak acceptance 1 9/26/2011 A. Multiple choice • A deductively valid argument cannot have… a. True premises and a false conclusion b. False premises and a false conclusion c. False premises and a true conclusion d. True premises and a true conclusion A. Multiple choice • When a claim is neither worthy of outright rejection nor deserving of complete acceptance, we should… a. Proportion our belief to the evidence b. Proportion our belief to background information c. Tentatively accept it d. Tentatively reject it A. Multiple choice A. Multiple choice • You are most likely to let your self‐interest get in the way of clear thinking when you… • Chief among possible reasons for doubting an expert (aside from conflicting expert opinion) is. . . a. Are indifferent to your circumstances b. Have a personal stake in the conclusions you reach c. Have no commitments d. Try to control your emotions A. Multiple choice • An argument with this form—“If p, then q. If q, then r. Therefore, if p, then r”—is known as… a. b. c. d. Modus tollens Hypothetical syllogism Modus ponens Disjunctive syllogism a. Handwriting b. Bias c. Grammatical errors d. His/her nationality A. Multiple choice • A slippery‐slope pattern of argument is fallacious when. . . a. It is hypothetical b. There is good reason to think that doing one action will inevitably lead to another undesirable action. c. There are only two possible results. d. There is no good reason to think that doing one action will inevitably lead to another undesirable action. 2 9/26/2011 A. Multiple choice • A deductive argument is intended to provide… a. b. c. d. Probable support for its conclusion Persuasive support for its conclusion Logically conclusive support for its conclusion Tentative support for its conclusion A. Multiple choice • A deductively valid argument that has true premises is said to be… a. b. c. d. Strong Sound Cogent Probable A. Multiple choice B. Short answer • This argument—“Either you support the war or you are a traitor to your country. You don’t support the war. So you’re a traitor”—is an example of. . . • Why is it important to critically examine your beliefs? a. b. c. d. False dilemma Begging the question Equivocation Innuendo B. Short answer • Guard against error and manipulation • Beliefs ground decisions, so better beliefs lead to better decisions B. Short answer • What is the difference between sentences that do and do not express statements? • Give an example of a cogent inductive argument. • The first category can be true or false, the second can’t • The second category includes questions, orders, interjections, etc. • Cogent = inductively strong + true premises • Example: ‘99% of people who buy lottery tickets don’t win. John bought a ticket. So it’s very likely that John will not win.’ 3 9/26/2011 B. Short answer B. Short answer • Why is asking someone to prove a universal negative unreasonable? • Universal negative: ‘There are no asteroids made of chocolate’ • It is hard to prove this because we can only base the claim on common sense and on the observation of a few asteroids we saw through telescopes. We haven’t inspected, and can’t inspect all asteroids in the Universe. • Give an example of a valid argument in which the premises are false. B. Short answer B. Short answer • Give an example of the ‘straw man’ fallacy. • Bread is a stone. Stones are nourishing. Therefore, bread is nourishing. • Give an example of a valid argument in which the conclusion is false. • ‘Senator Kennedy is opposed to the military spending bill, saying that it’s too costly. Why does he always want to slash everything to the bone? He wants a pint‐sized military that couldn’t fight off a crazed band of terrorists, let alone a rogue nation’ • If Obama is the president, then the moon is made of green cheese. The moon is not made of green cheese. Therefore, Obama is not the president. B. Short answer C. Logical form • Give an example of an inductive argument which is strong, but not cogent. • Strong = good inductive support. Not cogent = premises are false. • Example: ‘99% of the smokers die before the age of forty. So John, who is a smoker, will die before he reaches forty.’ • For the following argument, determine whether it is valid or invalid and indicate the argument pattern: • If the Pilgrims built that wall, [then] there would be archaeological evidence of that. But there is no such evidence. So the Pilgrims did not build that wall. • If p, then q. Not q. Therefore, not p. • Valid! 4 9/26/2011 C. Logical form • For the following argument, determine whether it is valid or invalid and indicate the argument pattern: C. Logical form • If laws could stop crime, there would be no crime. But there is crime. Therefore the laws cannot stop crime. • If p, then q. Not q. Therefore, not p. • Valid! • For the following argument, determine whether it is valid or invalid and indicate the argument pattern: • If it rains, Alex will get wet. If he gets wet, he’ll be upset. Therefore, if it rains, Alex will be upset. • If p, then q. If q, then, r. Therefore, if p, then r. • Valid! D. Diagramming D. Diagramming • (1) Most atheists are liberals, and (2) George is an atheist. Therefore, (3) George is probably a liberal. (4) Therefore, George is probably in favor of increased welfare benefits (5) because most liberalsare in favor of increased welfare benefits. D. Diagramming (1) We shouldn’t pay Edward an allowance (2) because he never does any work around the house, and (3) he will probably just waste the money because (4) he has no conception of the value of anything. (1) Most atheists are (1) + (2) liberals, and (2) George is an atheist. Therefore, (3) George is probably a liberal. (3) + (5) (4) Therefore, George is probably in favor of increased welfare benefits (5) because most liberals are (4) in favor of increased welfare benefits. D. Diagramming (1) We shouldn’t pay (2) (4) Edward an allowance (2) because he never (3) does any work around the house, and (3) he will probably just waste (1) the money because (4) he has no conception of the value of anything. 5 9/26/2011 E. Reverse diagramming ( 1) + (2 ) ( 3 ) + ( 4 ) E. Reverse diagramming ( 1) + (2 ) ( 3 ) + ( 4 ) (1) If the pipes are busted, there will be no running water. (2) The pipes are busted. (3) And if all the water is rusty, we won’t be able to use it anyway. (4) All the water is rusty. (5) So we have no usable water at this point. ( 5 ) ( 5 ) E. Reverse diagramming E. Reverse diagramming ( 1) + (2 ) ( 3 ) + ( 4 ) ( 5 ) (1) If the pipes are busted, there will be no running water. (2) The pipes are busted. (3) And if all the water is rusty, we won’t be able to use it anyway. (4) All the water is rusty. (5) So we have no usable water at this point. ( 1) + (2 ) ( 3 ) + ( 4 ) ( 5 ) (1) If the pipes are busted, there will be no running water. (2) The pipes are busted. (3) And if all the water is rusty, we won’t be able to use it anyway. (4) All the water is rusty. (5) So we have no usable water at this point. GOOD LUCK! 6 ...
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This note was uploaded on 12/20/2011 for the course PHIL 102 taught by Professor Rug during the Fall '11 term at University of Illinois, Urbana Champaign.

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