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  • Slide 1
  • Fallacies - Weak Induction
  • Slide 2
  • Homework Review: Fallacies pp. 103-105, 4.1 Fallacies in General pp. 121-131, 4.3 Fallacies of Weak Induction Inductive Argumentation Analogical Reasoning, e.g., ex. 8.4 Causal Argumentation, e.g., 8.3b Inductive Generalization, e.g., 8.2b Read for Next Class pp. 106-116, 4.2 Fallacies of Relevance
  • Slide 3
  • ANALOGICAL REASONING Induction Final Unit
  • Slide 4
  • Analysis Identify Subject and Analogue Criticism 1.Are common features relevantly similar to inferred feature? 2.Is there a disanalogy? Arguments from Analogy? Both my dog and my neighbor's dog are well- loved members of the family. Each one is well fed, house broken, walked on a regular basis. My dog has a very calm temperament. So I infer that my neighbor's dog also has a calm temperament.
  • Slide 5
  • WEAK INDUCTION Fallacies Transition
  • Slide 6
  • Kinds of Fallacies a defect or error traceable to the very structure (or form) of the argument a defect which can be detected only by reference to the content of an argument vsFormContent Formal FallaciesInformal Fallacies
  • Slide 7
  • Kinds of Informal Fallacies Fallacies of: 1.Relevance 2.Weak Induction 3.Presumption 4.Ambiguity a.Amphiboly/Equivocation b.Whole/Part See pages 153f for a complete list Only required to classify each fallacy according to these four types
  • Slide 8
  • Your Task on the Exam Explain how the argument is fallacious. Fallacies on Exam fallacy of relevance fallacy of weak induction fallacy of presumption fallacy of ambiguity none of the above
  • Slide 9
  • WEAK INDUCTION Fallacies
  • Slide 10
  • Weak Induction Inferential connection evidence not strong enough to support conclusion Premises are relevant to conclusion Premises do not warrant conclusion
  • Slide 11
  • The Five Fallacies of Weak Induction 1.Appeal to Ignorance 2.Appeal to Unqualified Authority 3.Hasty Generalization 4.False Cause 5.Weak Analogy In each case, 1.The premises are relevant to conclusion 2.Premises provide insufficient evidence to warrant conclusion In each case, 1.The premises are relevant to conclusion 2.Premises provide insufficient evidence to warrant conclusion
  • Slide 12
  • The Five Fallacies of Weak Induction 1.Appeal to Ignorance 2.Appeal to Unqualified Authority 3.Hasty Generalization 4.False Cause 5.Weak Analogy In each case, 1.The premises are relevant to conclusion 2.Premises provide insufficient evidence to warrant conclusion In each case, 1.The premises are relevant to conclusion 2.Premises provide insufficient evidence to warrant conclusion See earlier presentations for assessment criteria
  • Slide 13
  • The Five Fallacies of Weak Induction 1.Appeal to Ignorance Smoking has not been proven to cause cancer, therefore tobacco products are not carcinogenic Premises offer only a lack of evidence A definite assertion is made on this basis In each case, 1.The premises are relevant to conclusion 2.Premises provide insufficient evidence to warrant conclusion In each case, 1.The premises are relevant to conclusion 2.Premises provide insufficient evidence to warrant conclusion Exceptions 1.If search for evidence has been (seemingly) exhaustive by qualified personnel 2.American Legal Standard: reasonable doubt Exceptions 1.If search for evidence has been (seemingly) exhaustive by qualified personnel 2.American Legal Standard: reasonable doubt See in-class example: Mills Method of Residue
  • Slide 14
  • The Five Fallacies of Weak Induction 2.Appeal to Unqualified Authority I was speaking to my brother at his auto shop, and he believes the Democrats will lose Maryland in the next election. So I think its likely. Premises offer testimony/opinion from an authority Conclusion about subject matter is made on this basis In each case, 1.The premises are relevant to conclusion 2.Premises provide insufficient evidence to warrant conclusion In each case, 1.The premises are relevant to conclusion 2.Premises provide insufficient evidence to warrant conclusion Question rests on the relevant expertise of the authority consulted
  • Slide 15
  • The Five Fallacies of Weak Induction 3.Hasty Generalization See Presentation Induction: GeneralizationsInduction: Generalizations In each case, 1.The premises are relevant to conclusion 2.Premises provide insufficient evidence to warrant conclusion In each case, 1.The premises are relevant to conclusion 2.Premises provide insufficient evidence to warrant conclusion Two Issues Affecting Strength Representativeness of Sample Interviewer Bias Two Issues Affecting Strength Representativeness of Sample Interviewer Bias
  • Slide 16
  • The Five Fallacies of Weak Induction 4.False Cause Four variants (complex fallacy) a.Post hoc ergo propter hoc (after this, there because of this) b.Non causa pro causa (non-cause for the cause) c.Oversimplified cause d.Slippery Slope
  • Slide 17
  • The Five Fallacies of Weak Induction 4.False Cause: After we arrived, the baby got sick. So I think we were the cause of the babys illness. No causal relation apparent or explained Causal conclusion based on mere temporal succession after this In each case, 1.The premises are relevant to conclusion 2.Premises provide insufficient evidence to warrant conclusion In each case, 1.The premises are relevant to conclusion 2.Premises provide insufficient evidence to warrant conclusion
  • Slide 18
  • The Five Fallacies of Weak Induction 4.False Cause: Computer scientists do better at logic. So to do better in this course, you should study computer science Typically, no assertion of temporal succession Mistaken assertion of causal agency non-cause In each case, 1.The premises are relevant to conclusion 2.Premises provide insufficient evidence to warrant conclusion In each case, 1.The premises are relevant to conclusion 2.Premises provide insufficient evidence to warrant conclusion
  • Slide 19
  • The Five Fallacies of Weak Induction 4.False Cause: Your car is causing global warming. Phenomenon in question caused by complex number of factors A single one of these factors is asserted as sole cause oversimplification In each case, 1.The premises are relevant to conclusion 2.Premises provide insufficient evidence to warrant conclusion In each case, 1.The premises are relevant to conclusion 2.Premises provide insufficient evidence to warrant conclusion
  • Slide 20
  • The Five Fallacies of Weak Induction 4.False Cause: If you fail this class, then your GPA will go down. If you GPA falls, youll lose your scholarship. If you lose your scholarship, youll spend all your money on school. If you do this, youll have no money for food and shelter. So if you fail this class, you will become a starving, homeless beggar. A chain of causal events is asserted The causal connection between some or all events is highly unlikely At least the ultimate conclusion is highly unlikely slippery slope In each case, 1.The premises are relevant to conclusion 2.Premises provide insufficient evidence to warrant conclusion In each case, 1.The premises are relevant to conclusion 2.Premises provide insufficient evidence to warrant conclusion
  • Slide 21
  • The Five Fallacies of Weak Induction 5.Weak Analogy In each case, 1.The premises are relevant to conclusion 2.Premises provide insufficient evidence to warrant conclusion In each case, 1.The premises are relevant to conclusion 2.Premises provide insufficient evidence to warrant conclusion See earlier slides of this presentation! Two Issues Affecting Strength Common features relevantly similar to inferred feature No relevant dissimilarities (no disanalogy) Two Issues Affecting Strength Common features relevantly similar to inferred feature No relevant dissimilarities (no disanalogy)
  • Slide 22
  • Both my dog and my neighbor's dog are well- loved members of the family. Each one is well fed, house broken, walked on a regular basis. My dog has a very calm temperament. So I infer that my neighbor's dog also has a calm temperament. Arguments from Analogy?
  • Slide 23
  • Fallacies of weak induction Five identifiable kinds Not expected to provide the names of these on exam Fallacies on Exam In each case: 1.The premises are relevant to conclusion 2.Premises provide insufficient evidence to warrant conclusion In each case: 1.The premises are relevant to conclusion 2.Premises provide insufficient evidence to warrant conclusion
  • Slide 24
  • Homework Review: Fallacies pp. 103-105, 4.1 Fallacies in General pp. 121-131, 4.3 Fallacies of Weak Induction Inductive Argumentation Analogical Reasoning, e.g., ex. 8.4 Causal Argumentation, e.g., 8.3b Inductive Generalization, e.g., 8.2b Read for Next Class pp. 106-116, 4.2 Fallacies of Relevance