Category : Logic & Reasoning

Critical Thinking Logic & Reasoning Smart Thinking

Logical Fallacies: Faulty Deduction

The the last in this series of logical fallacies focuses on the mistakes we all make when making decisions and weighing information.

Anecdotes

Ignoring evidenced gained by a scientific approach in favour of firsthand stories or anecdotes.

Example: “My grandfather smoked 40 cigarettes per day, and he lived until he was 100, so why should I stop smoking?”

Composition

Assuming that the beliefs or characteristics of an individual apply to the entire group

Example: “The recent terrorist attacks were carried out by Islamic groups. Therefore all Muslims must be terrorists.”

Division

Conversely, assuming that the beliefs of a group apply to an individual member

Example: “Many Conservatives don’t believe in evolution, he’s a conservative, so he must also be a creationist.”

Design Fallacy

Assuming that because something is explained or visualised in a positive way, it must be truer.

Example: “Heaven.”

Gambler’s Fallacy

The assumption that the history of outcomes will affect future outcomes.

Example: “The roulette wheel has landed on Black 5 times in a row, I’m going to bet on Red because it’s bound to be read now.”

Hasty Generalisation

Drawing a conclusion from a narrow sample group.

Example: “I was almost hit today by two middle-aged women, women are terrible drivers.”

Jumping to Conclusions

Coming to a conclusion without considering all the evidence and possibilities.

Example: “He said he was working late, but I know he wasn’t in the office. He must be cheating on me”

Middle Ground

Assuming that because two opposing arguments are valid, that the truth will be found in some middle ground.

Example: “I think the car is worth £1,000, but you think it’s worth £5,000, so let’s meet in the middle at £3,000.”

Perfectionist Fallacy

Only valuing perfection and rejecting any solution which is less than perfect.

Example: “What’s the point in introducing stricter gun control, criminals will still be able to get hold of guns anyway?”

Relativist Fallacy

Rejecting a claim or idea because of a belief that the truth is relative.

Example: “That might be true for you, but it isn’t for me.”

Sweeping Generalisation

Applying a general rule too widely.

Example: “These boys are disruptive because they were raised by single mothers.”

Undistributed Middle

Assuming that because two things share characteristics that they are the same thing.

Example: “A scientific theory can be unproven. Evolution is a theory; therefore, evolution is an unproven idea.”

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Logical Fallacies: Cause and Effect

Circular Logic

A conclusion which relies on a premise which is based on the conclusion.

Example: “The Bible is the word of God – I know that because it says it in the Bible and it must be true because the Bible is the word of God.”

Denying the Antecedent

Assuming that a cause is based on the effect when there are multiple possible causes.

Example: “If you get a good degree, you’ll get a good job. If you don’t get a degree, you won’t get a good job.”

Ignoring a Common Cause

Claiming a link between 2 events, when there is a 3rd event which is likely to be the cause.

Example: “During the 60s  there was a sexual revolution, because of that people are dying of AIDS.”

Cum Hoc Ergo Propter Hoc

Claiming that 2 events that occur together must have a cause-effect relationship and assuming that correlation = cause.

Example: “Smart people wear glasses, so wearing glasses must make you smarter.”

Affirming the Consequent

Assuming that there’s only one explanation for an observation you’ve made.

Example: “Marriage usually results in children, so that’s why marriage exists.”

Post Hoc Ergo Propter Hoc

The claim that because one event followed another, it was caused by it. Another cause-effect fallacy.

Example: “Since Obama became president, ISIS has become more powerful. Therefore, Obama has caused the rise of ISIS.”

Two Wrongs Make a Right

If someone is wronged, then another wrong will cancel it out

Example: “They killed 100 of our soldiers, so we need to kill 100 of their soldiers to make it right.”

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Logical Fallacies: Manipulating Content

Converse to attacking a person or group to discredit their argument, manipulating content takes a person’s argument and twists it into something entirely different or to manipulate your argument to make it appear more persuasive.

Confirmation Bias

When you cherry pick evidence which confirms your existing beliefs, but ignore all evidence to the contrary as erroneous or irrelevant.

Example: Paying more attention to the 5 studies which show a link between vaccines and autism than the 1,000+ studies which disprove any link.

Suppressed Evidence

The deliberate neglect of relevant evidence/information which counters your own argument.

Example: “Iraq has weapons of mass destruction and so we should invade.” This ignores the reports that show no evidence of such weapons.

Biased Generalising

Using an unrepresentative sample of people to bolster your argument.

Example: “75% of people would vote for Bernie Sanders” Based on a poll only of students.

Ad Hoc Rescue

Trying to protect a belief or idea by revising the argument each time a flaw is found.

Example: “Apart from the freedom to live in any EU country, the millions of jobs it sustains, increased security, strong business links, lower import costs and greater political influence,  what has the European Union ever done for us?”

False Dilemma

Positioning two options as the only two options and deliberately hiding or suppressing alternatives.

Example: “You have to choose between the Republicans or the Democrats.”

Misleading Vividness

By describing a situation in detail, even if that situation is rare or unlikely in order to convince that it is more of a problem that it truly is.

Example: “After gay marriage was legalised, school libraries now stock same-sex literature. This means that primary school children are exposed to gay fairy tales and books which promote a gay lifestyle”.

Red Herring

Intentional introduction of irrelevant material to distract from the argument and alter the conclusion.

Example: “The Prime Minister doesn’t need to disclose his tax returns. After all, there are corporations who have billions of pounds in unpaid tax.”

Slippery Slope

The assumption that a single small step in one direction will lead to an inevitable chain of increasingly worse events.

Example: “If we introduce stricter gun control, the government will be more controlling and we’ll be living in a dystopian country”.

Unfalsifiability

Suggesting a claim or argument that is impossible to prove false, purely because there is no way to check it’s validity.

Example: “He is a Prophet and speaks the message of God.”

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Logical Fallacies: On the Offensive

When we disagree with someone, often it’s easier to try and discredit the person or to manipulate their argument in order to make it weaker and easier to attack. Generally, this occurs by attacking the person themselves, rather than attacking the content of the argument.

The below are common approaches that this can take:

Ad Hominem

Ignoring the argument itself and attacking the person making the claim.

Example: “Anyone who wants to leave the EU is just a racist.”

Circumstance Ad Hominem

Saying that a claim has no credibility because of the person’s own interest in the claim.

Example: “This study on the cancer-beating properties of cannabis was funded by the pharmaceutical companies and so can’t be trusted..”

Guilt By Association

Ignoring or discrediting a claim or an idea by associating it with an undesirable group.

Example: “So if you think that The Patriot Act is inhumane, does that mean you support terrorism?”

Genetic Fallacy

Attacking a claim’s cause or origin rather than it’s content.

Example: “Are you surprised that the rich don’t complain that tax havens are unfair?”

Straw Man

Exaggerating, distorting or overly simplifying a claim and then arguing against the manipulated claim.

Example: “You think that Syrians shouldn’t escape to the EU, so you’re saying that Syrians don’t deserve to live in the EU, that they’re lesser than you?”

Burden of Proof

Rather than trying to prove your claim, you expect the other person to prove your claim to be false.

Example: “God exists, if you can’t prove me wrong, then  am right.”

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Logical Fallacies: Appeals to Emotion

Appeals to emotion are deliberate manipulations and selective word choice in order to provoke an emotional reaction and to bypass rational thought.

Appeal to Flattery

Using a compliment to disarm and distract in order to slip in an unfounded claim which is accepted alongside the compliment. The compliments/flattery are a form of Trojan horse.

Example: “My intelligent followers will recognise that leaving the European Union is the only reasonable option.”

Appeal to Wishful Thinking

Stating that a claim is true or false simply because you hope that it is.

Example: “There must be life after death, otherwise it’s just emptiness.”

Appeal to Nature

Drawing parallels with nature to imply that your claim is correct.

Example: “Homosexuality is a sin, otherwise why don’t you see homosexual animals?” – this argument is wrong both rhetorically and factually.

Appeal to Fear

A claim which is made stronger by creating a sense of fear and terror.

Example: “If we don’t build a wall, soon Mexicans will steal the jobs of hardworking Americans.”

Appeal to Consequences

Similar to wishful thinking, this is where you argue that a belief is true or false mostly because you don’t want to believe the implications of the opposing belief.

Example: “The reports on weapons of mass destruction must be true, otherwise that would mean that we went to war with Iraq illegally.”

Appeal to Pity

This is quite common on TV talent shows. A person tries to use pity to influence or sway a person’s opinion.

Example: “He lost his wife 6 months ago, rejecting him would be wrong.”

Appeal to Ridicule

Manipulating, exaggerating or presenting an opponent’s argument to make it look ridiculous.

Example: “Beliving in God is just like believing in Santa Claus or the Easter Bunny.”

Appeal to Spite

Ignoring or dismissing a potentially valid argument due to a personal bias against the claimant.

Example: “Sally’s idea just won’t work, she’s too impractical.”

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