Logical Fallacies Flashcards
Argument ad Populum (Appeal to public)
The fallacy of appealing to the popularity of an idea.
People only use 10% of their brain power. Everyone knows that! This little factoid is entirely false, but it is a great example of why popular opinion doesn’t
make something so
Argument from Personal Incredulity
The fallacy that if you can’t imagine something happening, it couldn’t happen.
There is no way you failed your final! You studied for a week! Close your eyes and imagine you got an A. Now open them. You still failed. Wishing something doesn’t make it so.
Tu Quoque (You Too!)
The logical fallacy in which the topic at hand is diverted by appealing to hypocrisy.
This fallacy has been employed by every kid and pointed out by every parent in history. “But mom, you’re always on your phone.” Hypocrisy doesn’t make something false.
Argumentum ad Logicam (Argument to Logic)
The fallacy of assuming something is fake because the argument in support of it is false.
In ancient times, Aristarchus asserted that the sun was the center of the universe because fire is nobler than earth as the center is nobler than the margins. Right idea, wrong reason
Cum Hoc ergo Propter Hoc (With This, Therefore Because of This)
The fallacy of assuming that because X and Y are both true, that X must have caused Y.
Consumption of mozzarella cheese closely correlates with civil engineering doctorates awarded. You could conclude that pizza makes you smarter, but it wouldn’t be true.
Post Hoc ergo Propter Hoc (After This, Therefore Because of This)
The logical fallacy of assuming that because X always happens before Y, then X causes Y.
Shortly after the rooster crows, the sun comes up. This happens every morning without fail. Thus, the rooster must be causing the sun to rise.
Argumentum ad Antiquitatem (The Argument to Tradition)
The argument that it has “always been done this way.” When advising a friend not to invest in Henry Ford’s new company, a bank president said, “The horse is here to stay but the automobile is only a novelty.”
Argumentum ad Hominem (Argument Directed at the Person)
The error of attacking a person or a motive instead of an argument.
After Philip had listened to Jesus talk for a while he was really impressed with what Jesus was saying. He told Nathaniel who said, “Can anything good come from Nazareth?”
Argumentum ad Ignorantiam (Argument to Ignorance)
The fallacy of assuming something is true just because it hasn’t been proven false.
In 1546 John Heywood famously wrote “the moon is made of a greene cheese.” He probably didn’t believe it, but he couldn’t be proved wrong for over 400 years.
Argumentum ad Misericoridam (Argument to Pity)
The fallacy of distancing from the logical conclusion by appealing to human empathy.
In Shakespeare’s Julius Caesar, conspirators killed Caesar because he was a dictator. This was cool until Antony reminded the crowd how rich and generally awesome Caesar was.
Argumentum ad Nauseam (Argument of Repetition)
The fallacy of repeating something over and over again to establish its veracity.
Many bits of conventional wisdom fall into this category. “It’s always darkest before dawn.” Actually, it’s usually darkest around midnight. It’s generally coldest before dawn.
Argumentum ad Verecundiam (Appeal to Authority)
The fallacy of appealing to an authority to prove a point.
“X-rays will prove to be a hoax,” said Lord Kelvin. He may have been President of the Roya Society, but even he got things wrong every so often.
Appeal to Nature
The fallacy that everything natural is better than everything unnatural.
“God made dirt, so dirt don’t hurt.” Well, you can get ringworm and Valley Fever from dirt. Natural products can be better for you, but each needs to be evaluated on its own merits.
Ad Ridiculum (Appeal to Ridicule)
The fallacy in which mockery is substituted for reasoned argument.
When criticized for excessive drinking, Winston Churchill once quipped, “my dear, you are ugly, but tomorrow I shall be sober, and you will still be ugly.” Funny, but not sound logic.
Red Herring
An attempt to re-direct an argument to another issue which is easier to answer.
Red herrings were famously used to throw pursuing dogs off the trail of escaped fugitives. Changing the subject can have a similarly advantageous effect on a losing argument.
Straw Man
The fallacy of replacing an opponent’s argument with an extreme or simplistic version.
“Why do we spend so much money on Mars exploration just to find that was water there a few thousand years ago?” There are many reasons to explore Mars, not just to find water.
Circulus in Demonstrando (Circular Argument)
The fallacy of making the very assumption you are trying to prove.
Charles Dickens employed this argument in Great Expectations. “Well,” said Joe, “Your sister’s a master mind, a master-mind.” “What’s that” I asked. “Her.”
Dicto Simpliciter ad Dictum Secundum Quid (Destroying the Exception)
The fallacy in which an exception is treated as though it should be part of the general rule.
It is true that birds can fly. It is also true that a penguin is a bird. Therefore, penguins can fly. This sounds reasonable, but it is clearly not true. Birds can fly, but not all birds can fly.
Non Sequitur (It Does Not Follow)
The fallacy in which a conclusion is drawn from a fact that does not logically follow.
In The Importance of Being Earnest, Algernon says, “speaking of the science of Life, have you got the cucumber sandwiches cut for Lady Bracknell?” Clever but illogical.
Petitio Principii (Begging the Question)
The logical fallacy of assuming the statement under examination is true. “English is a useless class! Useless classes waste time. Who wants to waste time? We should get rid of English class.” Agreeing with the latter statement doesn’t prove the former.
Plurium Interrogationum (Complex Question)
A question with a built-in presupposition that is impossible to answer succinctly.
“Is your aunt still the queen of Monaco?” There is no queen of Monaco. My aunt never was the queen. And she’s not now. You cannot answer this question with a “yes” or “no.”
Slippery Slope Argument
Asserting that if we allow A to happen, then Z will consequently happen too, therefore A should not happen.
The problem with this reasoning is that it avoids engaging with the issue at hand, and instead shifts attention to baseless extreme hypotheticals. The merits of the original argument are then tainted by unsubstantiated conjecture.
