Presentation is loading. Please wait.

Presentation is loading. Please wait.

Argument in ordinary life: Change minds; influence people Last week Beliefs you already have Beliefs I want you to have Premises Conclusion (= Assumptions)

Similar presentations


Presentation on theme: "Argument in ordinary life: Change minds; influence people Last week Beliefs you already have Beliefs I want you to have Premises Conclusion (= Assumptions)"— Presentation transcript:

1 Argument in ordinary life: Change minds; influence people Last week Beliefs you already have Beliefs I want you to have Premises Conclusion (= Assumptions)

2 Philosophy is like ordinary life: Using arguments to change minds.

3 Philosophy is not like ordinary life: Using arguments for theoretical activity. Philosophy is like ordinary life: Using arguments to change minds.

4 Asking just to knowwithout worrying about how answers can be used or applied. Theoretical Activity

5 Asking just to knowwithout worrying about how answers can be used or applied. Doesnt mean theories have no application, just that we arent thinking about applications while theorizing.

6 Theoretical Activity Without theoretical activity, we wouldnt have electricity (for example). Asking just to knowwithout worrying about how answers can be used or applied. Doesnt mean theories have no application, just that we arent thinking about applications while theorizing.

7 When youre asking just to know, theres no need for rhetoric.

8 When youre asking just to know, theres no need for rhetoric. Rhetoric is tricky persuasion : trying to convince people of things whether or not theyre really true. (e.g., by appealing to emotion).

9 Michael Jackson didnt do anything wrong. Hes the greatest singer ever! When youre asking just to know, theres no need for rhetoric. Rhetoric is tricky persuasion : trying to convince people of things whether or not theyre really true. (e.g., by appealing to emotion).

10 Conclusion: Michael Jackson didnt do anything wrong. Premises: 1) Michael Jackson is the greatest singer ever.

11 Conclusion: Michael Jackson didnt do anything wrong. Premises: 1) Michael Jackson is the greatest singer ever. Assumption: 2) If Michael Jackson is a great singer, then he wouldnt do things that are wrong.

12 Conclusion: Michael Jackson didnt do anything wrong. Premises: 1) Michael Jackson is the greatest singer ever. Assumption: 2) If Michael Jackson is a great singer, then he wouldnt do things that are wrong. ?

13 Conclusion: Michael Jackson didnt do anything wrong. Premises: 1) Michael Jackson is the greatest singer ever. Assumption: 2) If Michael Jackson is a great singer, then he wouldnt do things that are wrong. 1a) Great singers make people happy. 2a) People who make people happy dont do things that are wrong. Ca) If MJ is a great singer, then he wouldnt do things that are wrong. ?

14 Conclusion: Michael Jackson didnt do anything wrong. Premises: 1) Michael Jackson is the greatest singer ever. Assumption: 2) If Michael Jackson is a great singer, then he wouldnt do things that are wrong. 1a) Great singers make people happy. 2a) People who make people happy dont do things that are wrong. Ca) If MJ is a great singer, then he wouldnt do things that are wrong. ? X

15 Rhetorical arguments pull the wool over the eyes of the audience.

16 Useful in practical activities... - advertising -politics -law

17 Useful in practical activities... - advertising -politics -law But not theoretical activities. If youre asking just to know, you dont want to trick yourself. Rhetorical arguments pull the wool over the eyes of the audience.

18 Three Types of Argument Last week I asked: What connects the premises with the conclusion?

19 Beliefs you already have Beliefs I want you to have ? ?

20 Beliefs you already have Beliefs I want you to have ? ? Logic.

21 Beliefs you already have Beliefs I want you to have ? ? Logic. Well, I liedsort of...

22 Beliefs you already have Beliefs I want you to have ? ? Logic. There are actually 3 ways for premises to be attached to conclusions.

23 Beliefs you already have Beliefs I want you to have Logic Generalization Explanation Deductive argument Inductive Argument Abductive Argument There are actually 3 ways for premises to be attached to conclusions.

24 Deductive If premises are true, conclusion must be true Three Types of Argument Inductive If premises are true, conclusion is probably true Abductive (different) The conclusion explains the premises.

25 Deductive Arguments

26 The Ideal : Logically valid All premises true Deductive Arguments

27 The Ideal : Logically valid All premises true Deductive Arguments Real Life : Logically valid All premises agreed upon between arguer and audience

28 Deductive Arguments ValidityTruth

29 Deductive Arguments Both of these are valid : All fish swim All sharks are fish All sharks swim ValidityTruth

30 Deductive Arguments Both of these are valid : All fish swim All sharks are fish All sharks swim All fish wear gold chains All sharks are fish All sharks wear gold chains ValidityTruth

31 Deductive Arguments Both of these are valid : All fish swim All sharks are fish All sharks swim All fish wear gold chains All sharks are fish All sharks wear gold chains ValidityTruth

32 Deductive Arguments ValidityTruth An argument can be invalid even when every statement in it is true. All fish swim All sharks are fish All pimps wear gold chains

33 Deductive Arguments ValidityTruth True or False -Premises -Assumptions -Claims -Beliefs -Ideas -Sentences Valid or Invalid -Arguments -Inferences

34 Deductive Arguments Quick Quiz: Last week I said that if an argument makes assumptions, the assumptions are necessary parts of the argument. Why are they necessary? A) Without them, the premises wont be valid. B) Without them, the conclusion wont be true. C) Without them, the argument wont be true. D) Without them, the argument wont be valid.

35 Deductive Arguments Begging the Question (p. 19): 1)God exists because the bible says so 2) Consumer Reports is reliable because it rates itself as reliable.

36 Deductive Arguments Begging the Question (p. 19): 1)God exists because the bible says so 2) Consumer Reports is reliable because it rates itself as reliable. Write out premises and conclusion. Whats the technical meaning of circular reasoning ?

37 Inductive Arguments

38 If the premises are true, then the conclusion is probably true.

39 Inductive Arguments Deductive inferences follow logically If Tim is taller than Andy and Andy is taller than Bill, its impossible for Bill to be taller than Andy.

40 Inductive Arguments Inductive inferences dont Deductive inferences follow logically If Tim is taller than Andy and Andy is taller than Bill, its impossible for Bill to be taller than Andy.

41 Inductive Arguments Inductive inferences dont If a woman isnt wearing a wedding ring, its still possible that shes married. Deductive inferences follow logically If Tim is taller than Andy and Andy is taller than Bill, its impossible for Bill to be taller than Andy.

42 Inductive Arguments Induction = Generalization Essential to science : If this salt dissolves in water, then all salt dissolves in water. Inferences about the world in general are drawn from a particular sample.

43 Inductive Arguments Mathematical claims are verified by deduction... Scientific claims are verified by induction. 2 + 2 = 4 Kangaroos dont lay eggs.

44 Inductive Arguments Deductive inferences are either valid or not validity doesnt come in degrees. Inductive inferences do come in degreessome generalizations are stronger than others.

45 Inductive Arguments Inductive Strength 1) Sample Size 2) Bias (is sample representative?)

46 Abductive Arguments The conclusion explains the premises. Inference to the Best Explanation

47 Abductive Arguments The conclusion explains the premises. Inference to the Best Explanation Inference is better than argument. You can state an inference as an argument, but its less useful.

48 Abductive Arguments Mendels inference: Genes explain patterns of inheritance in pea plants. The conclusion explains the premises.

49 Abductive Arguments Not an inference about genes in general drawn from observations of particular genes. Mendels inference: Genes explain patterns of inheritance in pea plants. The conclusion explains the premises.

50 Abductive Arguments Not an inference about genes in general drawn from observations of particular genes. Mendel never observed a gene. Mendels inference: Genes explain patterns of inheritance in pea plants. The conclusion explains the premises.

51 Abductive Arguments Copernicus didnt observe the planets orbiting the sun. Likewise,

52 Abductive Arguments Copernicus didnt observe the planets orbiting the sun. Likewise, Newton didnt observe gravity moving apples toward the ground.

53 Abductive Arguments Copernicus didnt observe the planets orbiting the sun. Likewise, Newton didnt observe gravity moving apples toward the ground. Darwin didnt observe natural selection.

54 Abductive Arguments Why inference to the best explanation? Abductive inferences involve hypotheses, and some hypotheses are better than others.

55 Abductive Arguments Why inference to the best explanation? Abductive inferences involve hypotheses, and some hypotheses are better than others. IF (hypothetically) the sun orbits the earth, THEN wed observe what we actually observe. GOOD

56 Abductive Arguments Why inference to the best explanation? Abductive inferences involve hypotheses, and some hypotheses are better than others. IF (hypothetically) the earth orbits the sun, THEN wed observe what we actually observe. IF (hypothetically) the sun orbits the earth, THEN wed observe what we actually observe. GOODBETTER

57 Abductive Arguments Like inductive arguments, they come in degrees. Abductive Arguments are Weird

58 Abductive Arguments Like inductive arguments, they come in degrees. But unlike inductive arguments, their strength doesnt depend on the strength (probability) of the premises. Abductive Arguments are Weird

59 Abductive Arguments Like inductive arguments, they come in degrees. But unlike inductive arguments, their strength doesnt depend on the strength (probability) of the premises. Abductive Arguments are Weird

60 Abductive Arguments Abductive Arguments are Weird An abductive argument just says the conclusion is one explanation of the premises. It doesnt say how good that explanation is, or whether a better one is available.

61 Abductive Arguments The Surprise Principle To evaluate an abductive inference (a hypothesis), you cant just look at whether any prediction it makes is true... EXAMPLE: Hypothesis: the patient is having a heart attack Prediction: the patient has a heart

62 Abductive Arguments The Surprise Principle You have to consider predictions that distinguish the hypothesis from other explanations. Alternative Hyp: the patient isnt having a heart attack....wed still predict that the patient has a heart. EXAMPLE:

63 Abductive Arguments The Surprise Principle You have to look at surprising predictions predictions you wouldnt make without that hypothesis. A prophet who predicts what everyone already expects to happen has no special powers.

64 Abductive Arguments The Surprise Principle For a hypothesis to be supported: 1)No false predictions 2) Some true predictions are surprising

65 Abductive Arguments The Only Game in Town Fallacy What if you only have one hypothesis, so you cant make comparisons?

66 Abductive Arguments The Only Game in Town Fallacy What if you only have one hypothesis, so you cant make comparisons? You can evaluate explanations by themselves, so you dont have to accept a bad explanation just because its the only game in town.

67 Abductive and Inductive Arguments An Investment Swindle (p. 37)...

68 Abductive and Inductive Arguments An Investment Swindle (p. 37)... Ten predictions in a row were correct. These ten are a representative sample. (Assum.) The investment firm has some way of knowing how well stocks will do. Hyp 1 Ten predictions in a row were correct. The investment firm got lucky ten times in a row. Hyp 2


Download ppt "Argument in ordinary life: Change minds; influence people Last week Beliefs you already have Beliefs I want you to have Premises Conclusion (= Assumptions)"

Similar presentations


Ads by Google