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Today we’re talking about logical fallacies. These are common patterns of reasoning cause us to make mistakes in how we argue or think about the world. Examples include: ad hominem, appeal to ignorance, and the gambler’s fallacy.
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My Notes
Introduction [00:00-00:29]
- A logical fallacy is a pattern of reasoning that:
- Weakens arguments
- Is an unreliable guide to truth
- Leads to bad inferences
- Learning fallacies helps with:
- Studying philosophy
- Getting better at arguments
Common Logical Fallacies
Ad Hominem [00:29-00:52]
- Attacking the person instead of addressing their argument
- Using an insult as the basis for concluding someone is wrong
- Note: Just insulting someone isn’t automatically an ad hominem
Appeal to Authority [00:52-02:24]
- Deferring to power or expertise instead of making direct arguments
- Two types:
- Appealing to authority with power (e.g., President)
- Appealing to expert opinion without considering evidence
- Problems with this approach:
- Experts are not infallible
- Expert consensus can be wrong (e.g., doctors once thought cigarettes were harmless)
- Conflicting authorities often disagree
- We should evaluate arguments and evidence, not just authority
Appeal to Emotion [02:24-03:11]
- Stirring up feelings to convince people rather than using logic
- Can be both positive and negative emotions
- Variations include:
Appeal to Popularity [03:11-03:46]
- Justifying beliefs based on how many people hold them
- Also called the Bandwagon Fallacy
- Popular beliefs can be (and often are) false
- Example: It was once widely believed the sun orbited Earth
Appeal to Heterodoxy [03:46-04:19]
- Taking disagreement as evidence of correctness
- Positioning oneself as a “bold truth-teller”
- Seeing lack of agreement as evidence for one’s beliefs
- The number of people who agree/disagree is irrelevant to truth
Value of Studying Logical Fallacies [04:19-05:12]
- When learning a new skill, we need:
- Positive examples to emulate
- Negative examples to avoid
- Logical fallacies are negative examples
- Studying logic helps identify valid arguments
Appeal to Tradition [06:13-06:38]
- Assuming something is true because it’s old or traditional
- Traditional beliefs can be false
- Some may argue traditions survive because they’re likely true, but this isn’t logically guaranteed
Appeal to Novelty [06:38-06:50]
- Believing something is true because it’s new
- The inverse of appeal to tradition
- Many new beliefs are also false
Appeal to Progress [06:50-07:07]
- Believing whatever will be believed in the future
- Problem: People in the future can also be wrong
Appeal to Hypocrisy [07:07-07:35]
- Arguing someone is wrong because they’re a hypocrite
- A moral failure doesn’t invalidate logical truth
- Example: Someone who lies can still correctly claim lying is wrong
Moralistic Fallacy [07:35-07:42]
- Thinking what is desirable must be true
Doomsayer Fallacy [07:42-07:51]
- Thinking what is undesirable must be true
- The inverse of the moralistic fallacy
Appeal to Moderation or Middle Ground Fallacy [07:51-08:19]
- Assuming the truth must be between two extreme positions
- Extreme proposals can be correct
- Moderate proposals can be correct
- Extremity or moderation doesn’t determine truth
Appeal to Ignorance [08:19-08:47]
- Assuming something is true because it hasn’t been disproven
- Example: Russell’s teapot orbiting the sun
Genetic Fallacy [08:47-09:06]
- Judging a belief based on its origins
- Origins of beliefs have little to do with their truth value
Guilt by Association [09:06-09:16]
- Dismissing beliefs because of others who hold them
Probability-Related Fallacies
Gambler’s Fallacy [09:16-09:42]
- Believing past random events affect future probabilities
- Example: A coin landing heads 99 times doesn’t change the 50% probability on the 100th flip
Hasty Generalization [09:42-10:04]
- Generalizing from too small a sample
- Example: Seeing two white dogs and concluding all neighborhood dogs are white
Hot Hand Fallacy [10:04-10:19]
- Assuming past success with random events predicts future success
- If events are truly random, past success doesn’t indicate future success
Formal Logical Fallacies [10:19-10:48]
- Unlike informal fallacies, these relate to logical operators
- Involve Boolean operators: if, and, or, not
Affirming the Consequent [10:48-11:06]
- If A then B; B, therefore A
- Example: If it’s raining, the sidewalk is wet. The sidewalk is wet, so it must be raining.
- Problem: Other things can cause a wet sidewalk
Denying the Antecedent [11:06-11:20]
- If A then B; not A, therefore not B
- Example: If it’s raining, the sidewalk is wet. It’s not raining, so the sidewalk isn’t wet.
- Problem: The sidewalk could be wet for other reasons
Begging the Question [11:20-11:31]
- Assuming what you’re trying to prove
- Including your conclusion in your premises
Equivocation [11:31-12:06]
- Using the same word with different meanings in an argument
- Example: “Every law requires a lawgiver. There are laws of nature. Therefore, nature has a lawgiver.”
- Problem: “Law” means different things in each premise
Straw Man [12:06-12:31]
- Misrepresenting someone’s position to make it easier to attack
- Similar to equivocation between the real position and the misrepresentation
No True Scotsman [12:31-13:05]
- Dismissing counter-examples by redefining terms
- Example: “No Scotsman puts sugar on porridge.” “I’m Scottish and I do.” “Well, no TRUE Scotsman does.”
Motte and Bailey [13:05-13:56]
- Switching between two positions:
- A radical position (bailey)
- An easily defensible position (motte)
- Example: “Defund the police” shifting between complete defunding and reallocating some funding
Slippery Slope [13:56-14:31]
- Assuming a minor change will lead to extreme consequences
- Only a fallacy when lacking evidence for the chain of events
- Sometimes incremental changes do lead to larger ones
Correlation vs. Causation [14:31-14:45]
- Assuming correlation implies causation
- Two events happening together doesn’t mean one causes the other
Fallacy of Composition [14:45-15:08]
- Assuming what’s true of parts is true of the whole
- Example: All cells in the body are microscopic, but the body isn’t microscopic
Fallacy of Division [15:08-15:15]
- Assuming what’s true of the whole is true of all parts
- The inverse of the fallacy of composition
Comparative Fallacy [15:15-15:27]
- Inferring an absolute claim from a comparative claim
- Example: A Rolex is cheaper than a Patek Philippe, but that doesn’t mean a Rolex is cheap
Conclusion [15:27-15:39]
- Acknowledges some fallacies may have been omitted
- Invites viewer discussion