Thread by @SahilBloom

Logical Fallacies are errors in reasoning that destroy the quality of an argument.

20 dangerous Logical Fallacies to identify and avoid:

Ad Hominem

Latin phrase for "to the person”—an attack of the individual rather than the argument.

Instead of addressing the argument’s merits, the offender attempts to refute the opposition on the basis of personal characteristics.

Common in political (and Twitter) debates.

Red Herring

The kippered herring was a smelly fish used to distract hunting dogs while training them to focus on a scent.

"Red herring" is now synonymous with distraction.

The offender distracts from the argument with a seemingly related—but actually unrelated—point.

The Texas Sharpshooter

A Texan fires a gun at a barn wall and then paints a target around the closest cluster of holes to create the appearance of a sharp shot.

The offender selects and highlights evidence that supports the conclusion—while ignoring evidence that may refute it.

Sunk Cost Fallacy

Sunk costs are economic costs already invested in an activity that cannot be recovered.

The fallacy is found in thinking that you should continue on the basis of all that you've put in—with no regard for future costs or likelihood of ultimate success.

Bandwagon Fallacy

An assumption of truth on the basis of the majority of people believing it to be true.

"Everyone believes X, so obviously X is true."

Typically offered without regard for the qualifications or ability of the people in question to validate the claim.

Straw Man

Setup a straw man to tear down.

The offender ignores the actual argument and replaces it with a flimsy, easily-refuted argument—a "straw man" to be torn down.

By replacing a strong argument with a weak one, the offender aims to create the illusion of a swift victory.

The Appeal to Authority

The over-reliance on the perspective of an "expert" to support the legitimacy of an argument.

The qualifications of the figure in the field of question must be considered.

Expert support can be a feature—but not the sole pillar—of the argument.

The False Dilemma

Only presenting two choices or alternatives when there are many more that exist.

This ignores nuance and lends itself to extreme positions.

Typically reduces the potential for compromise—as the two options are painted as being extremely far apart.

Post Hoc Ergo Propter Hoc

A flimsy argument framework that says since Event B followed Event A, Event B must have been caused by Event A.

Just because B followed A, doesn’t necessarily mean that B was caused by A.

Correlation ≠ Causation.

No True Scotsman

The "appeal to purity"—the changing of the original argument to evade a counter-argument.

You claim a Scotsman never drinks scotch with soda. Charles says he is a Scotsman and drinks scotch with soda. You exclaim that Charles must not be a true Scotsman!

Personal Incredulity

You cannot understand or believe something, so you argue that it cannot be true.

Complex topics often require significant upfront work to understand—an inability to do so immediately cannot be used to argue the illegitimacy of a claim.

Burden of Proof

The inability to provide evidence that a claim is false is used as justification that the claim is true.

Remember, the burden of proof always lies with the person making the claim to provide evidence.

The lack of refuting evidence IS NOT supporting evidence.

Hasty Generalization

Jumping to conclusions.

Substantial, wide-ranging conclusions are made on the basis of an immaterial, narrow body of evidence.

Insufficient evidence has been gathered to justify the claimed conclusions.

Non-Sequitur

The conclusion does not follow logically from the premises.

Presented evidence provides little or no actual support for the argument.

“Charles ate fish for dinner and is well-spoken, so he must be a banker.”

Tu Quoque

Latin for “you too” —attempting to discredit an opponent’s argument by pointing out personal behavior as being inconsistent with their argument.

Targeting the hypocrisy of the opponent.

“Don’t question my integrity, look at all of the bad things you’ve done!”

Slippery Slope

An argument that begins with a benign starting point before using a series of successive steps to get to a more radical, extreme end point.

No single step appears ridiculous on the surface, but the connection of multiple steps into a series is highly-improbable.

Begging the Question

A form of circular reasoning in which the argument is presented in such a way that the conclusion is included in the premise.

“Ghosts are real because I once experienced something that had to be a ghost.”

Easy to identify. The logic collapses on itself.

Loaded Question

Asking a question with a presumption built into the question (pre-loaded!).

Typically intended to be inflammatory in nature.

The individual on the receiving end of the question is forced to respond despite the baseless, irrelevant nature of the presumption.

Equivocation

Comes from the roots “equal” and “voice” - a single word or phrase can say two very different things.

Occurs when the offender uses a word or phrase in an intentionally misleading manner that sounds like it’s saying one thing but is actually saying something else.

The Fallacy Fallacy

Incorrectly assumes that a claim must be false if a fallacy was used to argue the claim.

Just because someone has poorly argued a claim, does not mean the claim itself is definitively false.

Those are 20 common—and dangerous—logical fallacies that destroy the quality of arguments.

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