PHI 1100: Ethics & Critical Thinking Sessions 23 & 24 May 5th & 7th, 2020 Evaluating Arguments: Sufficient Evidence, Reasonable Inferences, Respectful Argumentation 1 A good argument persuades readers/listeners by giving us adequate reason to believe that its conclusion is true. Ø Here are four basic criteria which will all be satisfied by a good argument: I. The premises are true. II. The premises provide sufficient evidence to believe that the conclusion is true. III. The conclusion follows logically from the truth of the premises. IV. It demonstrates the author’s respect for their readers/listeners. So far, we have discussed fallacies that involve: • the use of language to present false or misleading evidence • the use of statistics to present false or misleading evidence, insufficient evidence, or to make faulty inferences – This week we’ll go into more detail about fallacies involving the use of language to present 2 insufficient evidence or to make faulty inferences. A good argument persuades readers/listeners by giving us adequate reason to believe that its conclusion is true. III. The conclusion follows logically from the truth of the premises. • Fallacies that fail to satisfy this criterion of a good argument make faulty inferences: – they draw a conclusion that isn’t guaranteed (or extremely likely) to be true even if the premises are true. Ønon sequitur (Latin for ‘it doesn’t follow’) = when an argument draws a conclusion that just isn’t supported by the reasoning they have provided. ]P1] Dorothy is wearing red shoes today. [C] Obviously, red is Dorothy’s favorite color. » Many of the fallacies we’ll consider this week can be classified as subtypes of non sequiturs, • which draw particular types of conclusions from particular types of inadequate evidence. 3 Fallacies that involve making faulty inferences Ø hasty generalization = drawing conclusions about all members of a group or all instances of a phenomenon, after observing just a small sample of examples. This fallacy involves making inductive inferences from insufficient evidence. • Many stereotypes arise from hasty generalizations, and thereby believing them violates the requirement of total evidence. – Drawing conclusions on the basis of an inaccurate stereotype would be making a deductive inference from a false premise: [P1[ All Xs are Y. {P2] This individual is an X. [C] Therefore, this X is Y. If P1 is false (i.e., the stereotype does not describe all members of the group accurately), • then the conclusion that a particular individual fulfills the stereotype is not guaranteed to be true. 4 Fallacies that involve making faulty inferences • naturalistic fallacy = inferring that something is good just because it is “natural” (or bad because it isn’t natural) – (As mentioned when we discussed vagueness & weasel words, it’s often unclear on what qualifies something as natural vs. artificial: • the boundaries between these two categories aren’t clear cut, so it’s unclear which category a particular thing might belong in. – e.g., the active ingredient in aspirin (acetylsalicylic acid) can be extracted from some plants, but it’s most often synthesized by chemists in a lab; does that make it artificial, even though it occurs in nature?) [P1] Genetically modified foods are not found in nature. [C] Genetically modified foods should be banned. [P1] Viruses are part of nature. [C] Therefore, we shouldn’t try to kill the coronavirus or interfere with its spread. • Implied rule: The extent to which something is ”natural” is irrelevant to assessments of its value. 5 Fallacies that involve making faulty inferences Ø appeal to tradition = inferring that something is good just because it aligns with customs, traditions, or historical precedent (or bad because it is new, different, unorthodox, unprecedented…) – Just because something has been done a certain way for a long time doesn’t mean that’s how things should be, nor that things should continue that way in the future. Many appeals to tradition basically express people’s fear of the unknown. [P1] For most of human history, editing genetic code has been impossible. [C] Therefore, we should ban all gene-editing technologies. Ø appeal to novelty = inferring that something is good just because it is new & different An irrational attraction to whatever is new is no better (logically speaking) than attachment to tradition. Implied rules: The oldness/newness of something is irrelevant to assessments of its value. 6 Fallacies that involve making faulty inferences Ø false analogy = claiming that two things that have something in common (no matter how trivial) are thereby basically identical [P1] Ethylene glycol is a chemical. [P2] Ethylene glycol is extremely dangerous. [P3] Dihydrogen monoxide is also a chemical. [C] We must avoid dihydrogen monoxide at all costs. – Two things – like ethylene glycol (found in antifreeze) and dihydrogen monoxide (H2O, commonly known as water – can share some characteristics, but that doesn’t make them equivalent to each other or interchangeable. Implied rule: When discussing a complex phenomenon, acknowledge its full complexity instead of reducing it to a single characteristic. 7 Ø false dichotomy = claiming that there are only two options, positions, or interpretations for a topic, instead of recognizing that there are other alternatives (including both, somewhere in between, or none of the above) [P1] You’re either a cat person or a dog person. [P2] You don’t like cats. [C] Therefore, you’re a dog person. – A lot of false dichotomies show up in political discourse, in which people gravitate towards black-and-white, us vs. them thinking; • sometimes this involves proposing “purity tests” by which people must prove their allegiance to one side or the other (and are not allowed to remain on the fence or have a moderate stance). [P1] You aren’t in favor of all aspects of a capitalist economy. [C] Therefore, you are a communist. [P1] You prefer a public option for health insurance over completely abolishing the private health insurance industry. [C] Therefore, you are a practically a Republican. 8 A good argument persuades readers/listeners by giving us adequate reason to believe that its conclusion is true. II. The premises provide sufficient evidence to believe that the conclusion is true. We can think of evidence as “sufficient” when: a) an adequate amount of information has been provided b) this information is relevant to the conclusion c) this information comes from reliable sources d) this information is appropriate for the argumentative context – Let’s check out some common fallacies which involve the use of insufficient evidence, including: » not providing enough evidence » providing irrelevant evidence » providing unreliable evidence » providing inappropriate evidence 9 Fallacies that involve not providing enough evidence Ø anecdotal evidence = attempting to use one’s limited personal experience, or hearsay about someone else’s experience, as justification for a general conclusion – We could describe this as a subtype of hasty generalization. [P1] The G train came right away the one time I rode it. [C] The G train is totally reliable. As we discussed when we learned about the problem of induction, • one’s own personal experience (e.g., having only come across white swans) may not provide adequate insight to draw accurate generalizations (e.g., about the color range of swans). – Same goes for another person’s experience you learn about via testimony. – Implied rules: Don’t rely upon your own personal experience alone. • Seek a wider set of evidence reflecting other people’s experience, 10 many instances of observation under various circumstances, etc. Fallacies that involve not providing enough evidence Ø confirmation bias = ignoring or suppressing evidence that challenges the view defended in the conclusion; ”cherry-picking” particular sources &/or pieces of evidence that support a specific narrative, instead of presenting a more complete & accurate picture of the relevant evidence – Implied rule: The “requirement of total evidence”: • in order for either a belief or a conclusion to be justified, it should be based on consideration of all the evidence, not just part of it. 11 Fallacies that involve not providing enough evidence Ø Begging the question (a.k.a. circular argumentation) = when an author presupposes the truth of the conclusion within the reasoning they provide in defense of that conclusion. – Hence, the reasoning goes in a circle: it starts from where it intends to end (the truth of the conclusion), instead of providing distinct starting points that lead to inferring the conclusion. [P1] Nature exhibits intelligent design by a divine creator. [C] A higher power exists. • This argument begs the question, because [P1] contains an assumption that the patterns we observe in nature must have been created intentionally instead of arising through natural processes • Implied rule: Choose premises that could be believed to be true by individuals who haven’t yet committed to the truth of the argument’s conclusion. 12 Fallacies that involve not providing enough evidence Ø slippery slope = using premises that claim that making one change will inevitably lead to drastic undesirable consequences – This amounts to making bad inductive inferences about what will happen in the future (and/or lying for the purposes of fear-mongering): • guesses about what the future will bring are conjectures rather than facts, so these premises can’t be regarded as reliably true. [P1] If we legalize marijuana, next thing you know it’ll be legal to sell heroin to kids. [C] Therefore, marijuana use should be illegal. [P1] If you start using meth, you’ll end up turning to prostitution in order to pay for your drug habit. [C] Therefore, you shouldn’t start using meth. videos: bit.ly/2YpRf8k, bit.ly/2KVgPdu 13 Fallacies that involve providing irrelevant evidence Ø red herring = presenting information that has nothing to do with the truth of the conclusion, – usually for the purpose of distracting readers/listeners by drawing their attention towards something provocative that might shape their opinion of the argument’s topic.