1. Chapter 9:Evaluating Inductive Arguments II: Hypothetical Reasoning and Burden of Proof www.criticalthinking1ce.nelson.com Invitation to Critical Thinking First Canadian Edition Joel Rudinow Vincent E. Barry Mark Letteri

2. © 2008 by Nelson, a division of Thomson Canada Limited 9-2 Overview: Types of Inductive Reasoning  Presumptions and the “Burden of Proof”  Plausibility  Reasoning Hypothetically  Explanatory Power  Testing Hypotheses  Causal Reasoning

3. © 2008 by Nelson, a division of Thomson Canada Limited 9-3 Presumptions and the “Burden of Proof” “Burden of Proof” reasoning is a kind of inductive reasoning  Useful in resolving disputes that cannot be compromised or reconciled on a win/win basis  The greater the risk of error - and the higher the cost associated with being wrong - the heavier the burden of proof  Who has the burden of proof?

4. © 2008 by Nelson, a division of Thomson Canada Limited 9-4 Plausibility Plausibility is a measure of how well we think an idea is likely to survive critical scrutiny  The less plausible the arguer's position, the heavier the burden of proof  The affirmative side in a debate has the burden of proof because it is so much harder to prove the negative  Neither plausibility nor implausibility are absolute  Some claims are more plausible than others  In general, the more plausible the explanatory hypothesis, the stronger the inference

5. © 2008 by Nelson, a division of Thomson Canada Limited 9-5 Reasoning Hypothetically Inductive reasoning that consists in reasoning  from facts or observations  to explanatory hypotheses An “explanation” is an idea or set of ideas that succeeds in reducing or eliminating puzzlement. An “explanation” is an idea or set of ideas that succeeds in reducing or eliminating puzzlement. An “explanatory hypothesis” is an idea or set of ideas put forward for that purpose. An “explanatory hypothesis” is an idea or set of ideas put forward for that purpose. “Hypothesis” means supposition or conjecture. “Hypothesis” means supposition or conjecture.

6. © 2008 by Nelson, a division of Thomson Canada Limited 9-6 When reasoning hypothetically  The conclusion does not follow deductively from the premise  The premise makes it reasonable to suppose that the conclusion is true though there remains room for doubt about the truth of the conclusion though there remains room for doubt about the truth of the conclusion  The inference to a classification is a reasonable induction when The conclusion being true would explain the truth of the premise, or – The conclusion being true would explain the truth of the premise, or – The conclusion not being true would make the premise much more puzzling The conclusion not being true would make the premise much more puzzling

7. © 2008 by Nelson, a division of Thomson Canada Limited 9-7 The power of hypothetical reasoning lies in its capacity to extend or expand our knowledge of the world  Since hypothetical reasoning always takes us beyond what we already know, it always involves the risk of error  Just as with inductive generalizations the strength of an inference to an explanatory hypothesis is essentially a matter of how well the risk of error is managed or controlled. the strength of an inference to an explanatory hypothesis is essentially a matter of how well the risk of error is managed or controlled. no way exists to manage the risk of error in hypothetical reasoning on an individual inference-by-inference basis. no way exists to manage the risk of error in hypothetical reasoning on an individual inference-by-inference basis.

8. © 2008 by Nelson, a division of Thomson Canada Limited 9-8 Explanatory Power  Explanatory power of a given hypothesis the potential it offers to reduce or eliminate puzzlement the potential it offers to reduce or eliminate puzzlement  The greater the explanatory power of a given hypothesis, the stronger the inference  Relative explanatory power Compare the explanatory hypothesis under investigation with other hypotheses Compare the explanatory hypothesis under investigation with other hypotheses  When comparing equally powerful competing hypotheses or when several competing hypotheses are powerful Appeal to the plausibility standard when the explanatory power standard is not decisive Appeal to the plausibility standard when the explanatory power standard is not decisive Test hypotheses experimentally Test hypotheses experimentally

9. © 2008 by Nelson, a division of Thomson Canada Limited 9-9 Testing Hypotheses Hypothesis  An idea (or set of ideas) under investigation  To investigate hypotheses search for experimental evidence relevant to their truth or falsity search for experimental evidence relevant to their truth or falsity The scientific method The scientific method Use the hypothesis under investigation to predict thingsUse the hypothesis under investigation to predict things See whether or not the predictions turn out to be trueSee whether or not the predictions turn out to be true If what the hypothesis predicts turns out to be true that counts in favour of, or "confirms", the hypothesisIf what the hypothesis predicts turns out to be true that counts in favour of, or "confirms", the hypothesis If what the hypothesis predicts turns out not to be true that counts against, or "disconfirms", the hypothesisIf what the hypothesis predicts turns out not to be true that counts against, or "disconfirms", the hypothesis

10. © 2008 by Nelson, a division of Thomson Canada Limited 9-10 In testing hypotheses  We should search for both confirming and disconfirming evidence: The stronger the evidence, the more certain the prediction. The stronger the evidence, the more certain the prediction. Notice that disconfirming evidence weighs more heavily than confirming evidence. Notice that disconfirming evidence weighs more heavily than confirming evidence. Confirming evidence does not completely verify the hypothesis. Confirming evidence does not completely verify the hypothesis. But, notice that disconfirming evidence completely refutes it. But, notice that disconfirming evidence completely refutes it.  If we search thoroughly for disconfirming evidence and find none, that in itself constitutes a kind of confirming evidence. Referred to as "indirect confirmation" Referred to as "indirect confirmation"  Every unsuccessful attempt to falsify a hypothesis has the effect of strengthening it.

11. © 2008 by Nelson, a division of Thomson Canada Limited 9-11 Causal Reasoning David Hume  We never directly observe causal relationships  We have to infer them  We can never infer them with deductive certainty evidence for a causal relationship is always indirect since some room for doubt will always exist evidence for a causal relationship is always indirect since some room for doubt will always exist  We can reason about causes by means of simple inductive generalization turns out not to be very reliable turns out not to be very reliable inductive generalization by itself provides no basis for distinguishing between a causal relationship and a mere coincidence inductive generalization by itself provides no basis for distinguishing between a causal relationship and a mere coincidence

12. © 2008 by Nelson, a division of Thomson Canada Limited 9-12 Causal Reasoning John Stuart Mill  Method of Agreement The cause will be present in every instance in which the effect occurs The cause will be present in every instance in which the effect occurs The more isolated the common antecedent condition, the more likely it is to be causally related to the effect The more isolated the common antecedent condition, the more likely it is to be causally related to the effect

13. © 2008 by Nelson, a division of Thomson Canada Limited 9-13 Causal Reasoning John Stuart Mill  Method of Difference—a variation of simple inductive generalization  Look for a correlation between the absence of the effect and the absence of an antecedent condition  The method of difference is not absolutely conclusive any collection of individuals will have not one but many different antecedent conditions in common any collection of individuals will have not one but many different antecedent conditions in common most conditions will have no causal connection with the effect most conditions will have no causal connection with the effect  The cause will be absent from every instance in which the effect does not occur  The more isolated the difference, the more likely it is to be causally related to the effect

14. © 2008 by Nelson, a division of Thomson Canada Limited 9-14 Causal Reasoning John Stuart Mill  Method of agreement and the method of difference each enhance the reliability of inductive inferences about causal relationships when used separately  We can reasonably suppose that using them together would strengthen the inductive inference to a causal relationship even further

15. © 2008 by Nelson, a division of Thomson Canada Limited 9-15 Causal Reasoning John Stuart Mill  Method of Concomitant Variation  To apply the method of difference Find or experiment to bring about an instance in which a suspected causal antecedent condition is out of the picture Find or experiment to bring about an instance in which a suspected causal antecedent condition is out of the picture  When it is difficult or impossible to eliminate a suspected cause Vary it or observe its natural variations Vary it or observe its natural variations See whether these variations are accompanied by corresponding variations in the effect under investigation See whether these variations are accompanied by corresponding variations in the effect under investigation

16. © 2008 by Nelson, a division of Thomson Canada Limited 9-16 Exercise 9.9 In the first years of our century, so-called “reality television” became highly popular, noticeably pushing aside more traditional programming. Such shows typically featured documentary-style accounts of personal experiences—for example, romantic dates on The Bachelor or therapy sessions— and tests of skill or endurance—for example, Donald Trump’s The Apprentice (“You’re fired!”) and Fear Factor. “Documentary- style” is truly the appropriate term, since many such shows, though apparently aspiring to present “real life” experiences, were artificial in character. For example, none of the contestants on the huge hit Survivor, who were ostensibly stranded on the proverbial “desert island,” were ever in any real danger. Social critics wondered about the popularity of “reality television” shows and the implications for the general state of culture.

17. © 2008 by Nelson, a division of Thomson Canada Limited 9-17 Exercise 9.9  Consider the following list of explanatory hypotheses in terms of plausibility and explanatory power.  On this basis narrow the list down to two leading hypotheses.  Describe the kinds of experimental evidence that would then be needed in order to choose between the two finalists. Reality television shows featured “edgier” situations than traditional shows. Reality television shows featured “edgier” situations than traditional shows. So-called “reality” television exploited the public’s decreasing ability to distinguish fakeness from actual life. So-called “reality” television exploited the public’s decreasing ability to distinguish fakeness from actual life. It was just a fluke. It was just a fluke. It was novelty appeal. Traditional shows were simply getting old. People were looking for something new. It was novelty appeal. Traditional shows were simply getting old. People were looking for something new. Reality television was more challenging and rewarding intellectually than traditional shows. Reality television was more challenging and rewarding intellectually than traditional shows.