Toronto Metropolitan University Faculty of Arts SSH 105: Critical Thinking Professor David Hunter Chapter 4 Acceptable Reasons Chapter 4: acceptable reasons Critical thinking is reasonable thinking (in part) because it requires us to have good reasons for our conclusions. Reasons are good only when (i) they support our conclusions and (ii) they are acceptable. In this chapter, we will consider when our reasons for believing are acceptable. Evidence is acceptable when (i) it comes from a reliable source and (ii) it is neither undermined nor overridden by other evidence that we have. A source of evidence is reliable when it provides accurate information most of the time. –Reliability is a matter of degree. –Reliability depends on optimal conditions. –Reliability is topic-relative. When Evidence Conflicts Two bits of evidence are in direct conflict when one indicates that something is true and the other indicates that it is false. If one piece is stronger than the other, then the first overrides the second. Over-ridden evidence is not acceptable. Evidence is overridden when – It conflicts with evidence from a known reliable source; – It directly conflicts with expert consensus; – It directly conflicts with what we already have good reason to believe. When Evidence Conflicts Two bits of evidence are in indirect conflict when one indicates that the other is not acceptable. If the first is stronger than the other, then the first undermines the second. Undermined evidence is not acceptable. Critical Thinking Mistake: Appeal to ignorance It is a mistake to believe something just because you do not have evidence that it is false. We have a duty as critical thinkers to make sure – that our sources are reliable – that there is no conflicting evidence Observation and memory Observation is a source of evidence and memory is a kind of store-house for evidence. But before we trust either one we need to ask: – – – Is it reliable for this topic? Is it reliable enough? Are the conditions optimal? • List three topics on which direct visual observation is not reliable? • Describe a situation where direct visual observation is reliable on a topic but the conditions are not optimal. Testimony Testimonial evidence is acceptable only if: – – – – It is on an appropriate topic The witness is properly trained The witness is properly informed The witness is unbiased. The evidence must be on an appropriate topic. On some topics there are no experts. • Matters of personal taste or preference. – E.g., whether Springsteen is better than Eminem. • Where the facts are too complex. – E.g., why stock market goes up or down within a few hours • Where there is no settled expert opinion. – E.g., the leading edge of scientific investigation. The witness must be properly trained. The witness must be properly informed. The witness must be unbiased. Testimony Note 1: These four conditions are independent. – So you have to check each one. Note 2: If you think that some testimony is not acceptable, then have to say which of the conditions it fails to meet. Note 3: Testimony that is not acceptable might still be true! – Even biased fools can speak the truth. you Sometimes the proper thing for a critical thinker to do is to withhold belief. Advertising and the Media Advertising and news reports are just special cases of testimony. Advertising Celebrities are often used to help sell products, even though they are not trained, informed or unbiased. Should they be trusted? News Media • Some reporters are not trained experts on the issues. • Reporters are informed by sources, and some sources are anonymous. • Sometimes, reporters simply repeat what their sources say without thinking critically about it (passive reporting). News is prone to several kinds of bias – Reporter Bias – Corporate Bias – Cultural Bias Academic Journals Even Academic results need to treated with caution. – Overstating results – Funding bias The case of dark chocolate. – Publishing Bias Don’t publish negative inconclusive results. Don’t publish failures to reproduce studies Surveys Opinion polls are a familiar source of evidence. We use questionnaires to find out what people believe about some topic or other. We can use what we learned about testimony to figure out when survey results are acceptable. Evidence from a survey is acceptable just in case (i) the survey questions are not bad (ii) the survey subjects are properly trained informed (iii) there is no researcher or subject bias and If a question is ‘bad’ then asking it is not a reliable way to find out what the answerer believes. --ambiguous/vague, ‘Are you happy?’ --charged/slanted. ‘Do you think that students should be forced to pay more tuition?’ --loaded, ‘Have you stopped cheating on exams?’ --badly ordered, ‘Is it OK to smoke while you pray?’ The survey subjects must be properly trained and informed Public opinion polls often ask people about topics on which they lack training or information. Forcing them to take a position may disguise the fact that they really are agnostic or undecided. Survey results are acceptable only if there is no bias. Subject bias: the subjects might be motivated to lie or exaggerate. Researcher bias: those asking the questions might bias the results by the way they ask the questions. A double blind survey is one with questions on many different topics where neither the subject nor the questioner knows which is the target one. A recent poll in the US found that