Faulty Deduction

Rhetorical fallacies are subtle errors in speech and writing. – The manipulation of rhetoric and logical thinking. The following fallacies can be categorised as ‘Faulty Deduction’.

Anecdotal evidence

Discounting evidence arrived at by systematic search or testing in favour of a few firsthand stories.

“I’m going to carry on smoking. My grandfather smoked 40 a day and lived until he was 90!”


Assuming that characteristics or beliefs of some or all of a group applies to the entire group.

“Recent terrorists attacks have been carried out by radical Islamic groups. Therefore all terrorists are Muslims.”


Assuming that characteristics or belief of a group automatically apply to any individual member.

“Many Conservatives wish to ban gay marriage, discredit climate change, and deny evolution. Therefore all conservatives are homophobic, anti-environmental creationists.”

Design fallacy

Assuming that because something is nicely designed or beautifully visualised it’s more true.”

“Everything Shakespeare has written must be true.”

Gambler’s fallacy

Assuming the history of outcomes will affect future outcomes.

“I’ve flipped this coin 10 times in a row, and it’s been heads. Therefore the next coin flip is more likely to come up tails.”

Hasty generalisation

Drawing a general conclusion from a tiny sample.

“I just got cut off by the woman driver in front. Women can’t drive.”

Jumping to conclusions

–Drawing a quick conclusion without fairly considering relevant (and easily available) evidence.

“She wants birth control in her medical coverage? What a slut!”

Middle ground

Assuming because two opposing arguments have merit, the answer must lie somewhere between them.

“I rear ended your car but I don’t think I should pay for all the damage. A fair compromise would be split the bill in half.”

Perfectionist fallacy

Assuming that the only option on the table is perfect success, then rejecting anything that will not work perfectly.

“What’s the point of this anti-drunk driving campaign? People are still going to drink and drive no matter what.”

Relativist fallacy

Rejecting a claim because of a belief that truth is relative to a person or group.

“That’s perhaps true for you. But it’s not true for me.”


Assuming an observation from a small sample size applies to an entire group.

“This large shoe manufacturer employs children in sweatshops. Therefore all shoe companies are evil child-slave owners!”

Sweeping generalisation

Applying a general rule too badly.

“Those young men rioted because they lacked morally responsible fathers.”

Undistributed middle

Assuming because two things share a property, that makes them the same thing.

“A theory can mean an unproven idea. Scientists use the term evolutionary theory. Therefore evolution is an unproven idea.”

See other: Rhetorical Fallacies


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