PHILOSOPHY 102 INTRODUCTION TO LOGIC PRACTICE EXAM 1 W# Section (10 or 11) 1. True or False (5 points) Directions: Circle the letter next to the best answer. 1. T F All true statements are valid. 2. T F All valid arguments are sound. 3. T F A counterexample is an exception that proves the rule. 4. T F The statements that compose a disjunction are called conjuncts. 5. T F In the sentence John will go if Suzie goes, the consequent is John will go. 2. The Counterexample Method (25 points) Directions: Using the scheme of abbreviation provided, state the form of the arguments below. Then use the counterexample method to show that it is invalid. It is best to employ terms whose interrelations are well known, such as cat, dog, collie, mammal, and animal ; or, square, triangle, 3-sided, 4-sided, plane figure, and geometrical figure. If you must, you can use fire and air and the like. (1) If Morris is the best rebounder, then Steve is the best scorer. Morris not is the best rebounder. So, Steve is not the best scorer. (C = Morris is the best rebounder; S = Steve is the best scorer) (2) The Vikings will continue to play well given that the starting five stay healthy. Therefore, the Vikings will continue to play well. (V = The Vikings will continue to play well; H = The starting five stay healthy) 1
3. The Famous Forms Method (25 points) Directions: Using the scheme of abbreviation provided, state the form of the argument. Then use the famous forms method to argue that it is valid. If it s morally alright to use aborted human fetuses for research purposes, then it s morally alright to manufacture human fetuses for research purposes. It is not morally alright to manufacture human fetuses for research purposes. So, it s not morally alright to use aborted human fetuses for research purposes. (U = It s morally alright to use aborted human fetuses for research purposes; M = It s morally alright to manufacture human fetuses for research purposes) 4. Well-Crafted Arguments (15 points) Directions: State a scheme of abbreviation for the statements that constitute the following argument and then put the argument into well-crafted form. Be sure to eliminate excess verbiage. As Doestoevsky never tired of pointing out, especially in Brothers Karamozov, if there is no God, then there is no meaning and significance to life. Now, as even that rock-star biologist, Richard Dawkins, who s probably the world s most famous atheist at the moment, would have to admit, people almost invariably hang on to life even in the most dire circumstances. But if that s the case, then life has meaning and significance. It is difficult to avoid the conclusion that there is a God, after all. 2
5. Enthymemes (15 points) Directions: State a scheme of abbreviation for each of the statements in the following arguments, and then put the argument into well-crafted form. Be sure to supply the missing premises or conclusion. And remove verbiage. (1) I ve been thinking about moral responsibility and freedom a lot lately. I came across a pretty cool argument. If what we do is determined by things outside our control, then we are not morally responsible for what we do. If what we do happens by chance, then we are never free. Either what we do is determined by things outside our control or what we do happens by chance. It goes without saying that something remarkable follows. (2) Zeno had an interesting argument against the very possibility of motion. It went like this. If we can walk across the room, then we have to traverse infinitely many regions of space. Therefore, despite how things look to us, we cannot walk across the room. I wonder what to say about it? (3) Either she s tall or she s short. Therefore, she s tall. 3
6. Definitions (15 points) Directions: Fill in the blanks and answer the questions. Note: Exam 1 will include 15 of the 33 items below. See the textbook summaries of definitions for (nearly) all the answers. 1. Logic is 2. What is an argument? 3. What is a statement? 4. To say a statement is true is to say that 5. To say a statement is false is to say that 6. What is a deductive argument? 7. What is an inductive argument? 8. To say that an argument is valid is to say that 9. To say that an argument is invalid is to say that 10. To say that an argument is sound is to say that 11. To say that an argument unsound is to say that 12. What is an argument form? 13. What is a substitution instance of an argument form? 4
14. What is a valid argument form? 15. To say that an argument is formally valid is to say that 16. What is a conditional statement? 17. What are the parts of a conditional statement called? 18. What is a negation? 19. What is a disjunction? 20. What are the parts of a disjunction called? 21. What is modus ponens? 22. What is modus tollens? 23. What is disjunctive syllogism? 24. What is hypothetical syllogism? 25. What is constructive dilemma? 26. What is the fallacy of denying the antecedent? 27. What is an invalid argument form? 5
28. What is a counterexample to an argument form? 29. What is a good counterexample to an argument form? 30. What is the fallacy of affirming the consequent? 31. What is a well-crafted version of an argument? 32. What are the names of the four ways in which an argument can have excess verbiage? 33. What is an enthymeme? 7. Extra Credit (18 points) Write out a scheme of abbreviation for the statements contained in the following argument, put the argument into well-crafted form using capital letters, eliminating enthymemes, and then employ either the famous forms method to show that it is valid or the counterexample method to show that it is invalid. When I was growing up, my mother always used to say, One bird in the hand is better than two in the bush. I think she was right. Interestingly, she was right only if it is generally better for us to be content with the good things that we have rather than to strive for good things without getting any at all. The conclusion is obvious. 6