Unit 8: Informal Fallacies II

Assuming that because one event followed another, the first caused the second.

"I started wearing a lucky bracelet, and since then I have not had a cold. The bracelet is preventing illness."

Temporal sequence (A before B) is necessary for causation but not sufficient. Many things happen before many other things without causing them.

Assuming that two things that occur together are causally related. This is the classic correlation-causation confusion.

"Ice cream sales and drowning rates both increase in summer. Ice cream causes drowning."

Both are caused by a third variable (hot weather), not by each other.

Any error in which a non-causal relationship is treated as causal. This is the umbrella term for all causal fallacies.

"Countries with more television sets per household have higher life expectancy. Therefore, buying more televisions increases life expectancy."

Claiming that if one event is allowed to occur, a chain of increasingly bad consequences will inevitably follow — without justifying why each step in the chain is necessary.

"If we allow students to retake one exam, soon they will expect to retake every assessment, and eventually grades will become meaningless."

Drawing a broad conclusion from a sample that is too small or unrepresentative to support it.

"I met two people from that city who were rude. People from that city are rude."

Using a personal experience or a single isolated case in place of systematic evidence.

"My grandfather smoked every day and lived to 95. Smoking cannot be that dangerous."

Selecting data that supports a predetermined conclusion while ignoring the rest. The name comes from a mythical shooter who fires at a barn, then draws a target around the bullet holes.

"This dietary supplement has been tested 100 times. In 6 trials it outperformed the placebo — proof that it works." (The arguer ignores the 94 trials showing no effect.)

Drawing conclusions from a sample that does not reflect the population being studied.

"Our survey of 500 social media users found that 90% support this policy. The public overwhelmingly supports it." (Social media users are not a representative sample of the general public.)

Using statistics as evidence when they are biased, cherry-picked, or inapplicable to the claim.

"Our new drug reduces the risk of heart attack by 50%." (The risk fell from 2% to 1% — a 50% relative reduction, but only a 1% absolute reduction in real terms.)

Including the conclusion in the premises — or assuming what needs to be proved.

"This book must be true because it says so, and what it says is always true."

Claiming that the burden of proof lies with the person disputing a claim, rather than with the person making it. The principle: extraordinary claims require extraordinary evidence; the burden falls on the claimant.

"Prove that this herbal supplement does not cure cancer. Until you can, I will continue to take it."

A question that presupposes a claim which the respondent has not accepted. Any answer to the question appears to confirm the presupposition.

"Have you stopped cheating on your expenses?" (Answering either yes or no implies the person has cheated.)

Using a word or phrase with more than one meaning and shifting between meanings within an argument.

"The sign said 'fine for parking here.' So I parked there." (The sign uses "fine" to mean a penalty; the driver interprets it as permission.)

Arguing that because something is natural, it is therefore good, safe, or preferable — and that artificial things are bad.

"This product is completely natural, so it has no side effects." (Arsenic and botulinum toxin are natural; many life-saving medicines are synthetic.)

Assuming that a compromise between two positions must be correct. Sometimes the truth is not in the middle — one side may simply be right.

"You say climate change is driven by humans; the other side says it is entirely natural. The truth must be somewhere in the middle."

Claiming that because you cannot understand how something works, it is probably not true or impossible.

"I cannot understand how vaccines train the immune system, so I don't believe they work."

Believing that past random events affect the probability of future independent events. Each spin of a roulette wheel is independent of all previous spins.

"The coin has landed heads ten times in a row. It is bound to be tails next time."

1. Appeal to Nature — "natural" does not mean safe or beneficial. Many natural substances are harmful; many synthetic ones are beneficial.
2. Post Hoc Ergo Propter Hoc — the coffee drinking preceded her success, but that does not establish it as the cause. Many other factors contributed to her career.
3. Burden of Proof — the burden of proof lies with the person making the claim, not with those who remain sceptical. "You cannot disprove it" is not evidence for it.
4. Misleading Statistics — a 40% relative reduction sounds dramatic, but the absolute reduction is only 0.2 percentage points (from 0.5% to 0.3%). The relative framing exaggerates the effect size.
5. Gambler's Fallacy — each coin flip is an independent event. Past results have no influence on future outcomes for a fair coin.
6. Begging the Question (Circular Reasoning) — the Bible's authority is assumed to prove its own truth, and its truth is assumed to establish its authority. The argument goes in a circle.