Logic - chap. 1 - arguments

1. Logic - chap. 1 - arguments • What is logic? • The study of the principles used to distinguish between good and bad arguments. • Clarifications • Logic is not the study of the reasoning process • Logic is not primarily concerned with establishing the truth or falsity of statements. Logic; chapter 1 - slide 1

2. Logic - chap. 1 - arguments • Why are arguments important? • A way to resolve disagreements peacefully • Part of the process of finding the truth • For conceptual questions, arguments may be the principal method of determining truth • Central to our humanness Logic; chapter 1 - slide 2

3. Logic - chap. 1 - arguments • The notion of an argument • A set of statements of which one or more are put forward as reasons for accepting another statement as true. Logic; chapter 1 - slide 3

4. Logic - chap. 1 - arguments • An example of a simple argument • If we interfere with the publication of false and harmful doctrines, we shall be guilty of suppressing the liberties of others, whereas if we do not interfere with the publication of such doctrines, we run the risk of losing our own liberties. We must interfere or not interfere with the publication of false and harmful doctrines. Hence we must either be guilty of suppressing the liberties of others or else run the risk of losing our own liberties. Logic; chapter 1 - slide 4

5. Logic - chap. 1 - arguments • Distinguishing between arguments & non-arguments • Examples Logic; chapter 1 - slide 5

6. Logic - chap. 1 - arguments • I don’t think it would be a good idea to take the American Revolution course this term, because it conflicts with a course I need for my major, and my schedule would have more balance if I took a science course instead. • Nearly half the homes in the country subscribe to cable TV. Basic cable service usually includes local TV channels, such as the four networks, and one or more channels. For an additional fee, subscribers can also receive movie channels and other specialized programs Logic; chapter 1 - slide 6

7. Logic - chap. 1 - arguments • Analyzing arguments • 3 steps • (1) Identify & distinguish between premises & conclusion(s) • Clues • premises & conclusion may occur in any order Logic; chapter 1 - slide 7

8. Logic - chap. 1 - arguments • Example: No coal tar derivatives are nourishing foods, because all artificial dyes are coal tar derivatives, and no artificial dyes are nourishing foods. • look for indicator words • don’t let flourishes & repetitions confuse you Logic; chapter 1 - slide 8

9. Logic - chap. 1 - arguments • Example: In the twentieth century, physicalism has flourished. But the after-image is not in physical space. The brain-process is. So the after-image is not a brain-process. (J.J.C. Smart, “Sensations and Brain Processes,” Philosophical Review, April 1959) Logic; chapter 1 - slide 9

10. Logic - chap. 1 - arguments • missing Ps & Cs do not make an argument invalid (or weak) • Example: Mary attended the opera; so her lamb must have attended the opera too. • several arguments may be strung together Logic; chapter 1 - slide 10

11. Logic - chap. 1 - arguments • Example: (1) And now the great question as to the reason why. (2) Robbery had not been the object of the murder, for (3) nothing was taken. (4) Was it politics, then, or was it a woman? (5) That was the question which confronted me. (6) I was inclined from the first to the latter supposition. Logic; chapter 1 - slide 11

12. Logic - chap. 1 - arguments • Example (cont’d): (7) Political assassins are only too glad to do their work and to fly. (8) This murder had, on the contrary, been done most deliberately, and (9) the perpetrator had left his track all over the room, showing that he had been there all the time. (10) It must have been a private wrong, and not a political one, which called for such a methodical revenge. Logic; chapter 1 - slide 12

13. Logic - chap. 1 - arguments • (2) Analyze the structure of the argument • A strategy • (1) list & number each independent clause • (2) use arrows to indicate the relationship between Ps & Cs • (3) use + to indicate that two premises together entail the conclusion Logic; chapter 1 - slide 13

14. Logic - chap. 1 - arguments • (4) use separate arrows to indicate that premises independently support a conclusion • (5) indicate whether several arguments are linked in a series Logic; chapter 1 - slide 14

15. Logic - chap. 1 - arguments • Example of portraying the structure of an argument • It is rarely economical for two companies to lay cable in the same area and compete directly. This suggests that cable television is a natural monopoly, and should be regulated by the government. Logic; chapter 1 - slide 15

16. Logic - chap. 1 - arguments • Another example • (1) I can’t think of anything more futile than worrying about the past. (2) Did you ever meet anyone who could change the course of past events? (3) Of course not. Past events are entirely outside of human control. (4) Think of all the people who continually worry about their past lives, as if worrying made a difference. Logic; chapter 1 - slide 16

17. Logic - chap. 1 - arguments • Example (cont’d): (5) I’m sure that if these people would devote as much time and energy to present opportunities as they spend mulling over the past, they would be far better off. (6) I repeat, it’s futile to worry about the past, (7) because the past is something that can’t be controlled. Logic; chapter 1 - slide 17

18. Logic - chap. 1 - arguments • (3) Determine whether the argument is deductive or inductive • A traditional way of distinguishing • Deductive  general to specific • Inductive  specific to general • The weakness of this way of distinguishing between deduction & induction Logic; chapter 1 - slide 18

19. Logic - chap. 1 - arguments • An alternative and better way of distinguishing between deduction & induction • Induction  an argument in which the conclusion goes beyond the premises and accordingly the relationship between the premises & conclusion is one of probability • conclusions go beyond, make a leap into the unknown Logic; chapter 1 - slide 19

20. Logic - chap. 1 - arguments • Deduction  an argument in which the conclusion is implicitly contained within the premises and which, accordingly, has a relationship of necessity between the premises & conclusion • The function of deductive arguments  to clarify, to make explicit • The function of inductive arguments  to lead to new knowledge Logic; chapter 1 - slide 20

21. Logic - chap. 1 - arguments • Which of these two types of arguments is better? • the tradeoff  rigor, precision, guarantee that the conclusion is true if the premises are true vs new knowledge, discovery, prediction Logic; chapter 1 - slide 21

22. Logic - chap. 1 - arguments • Clues for distinguishing between inductive & deductive arguments • Look at the kind of claim being made • Deductive arguments often, not always, move from general to specific; inductive arguments often, not always, move from specific to general • To chapter 2 Logic; chapter 1 - slide 22