Logical Fallcies Critical Thinking

Equivocation

-an informal logical error where a key word or phrase changes meaning within an argument, making an unsound argument appear valid

-Example: Light things can’t be dark, feathers are light, therefore a feather can not be dark (light as a color and as light as a weight)

Denying the antecedent (formal fallacy)

A→B

~A (not A)

so, ~B (Not B)

Example: All dogs are mammals

Lily is not a dog

So Lily is not a mammal

(she could be another kind of mammal)

affirming the consequent (formal fallacy)

A→B

B is true

so A

Example: All dogs are mammals

Lily is a mammal

So Lily is a dog

(she could be another type of mammal)

Non-sequitor or red herring

-generic fallacies of irrelevance

-”it does not follow”

-intentional distraction

Ad Homminem

-fallacy of irrelevance/relevance

-attacking the person instead of the argument when it’s irrelevant

-Example: Timmy is ugly so he can’t be a good boss

Straw Man

-fallacy of irrelevance/relevance

-distorting/weakening the viewpoint to make it easier to attack

-Example: “We need to invest more money into extracurriculars for students.”

“so, you just want to stop kids from being able to learn the fundamentals of education.”

Appeal to Ignorance

-fallacy of relevance/irrelevance

-using ignorance as evidence/using a lack of evidence as your evidence

-shifts burden of proof to other person

-Example: “well you can’t prove that aliens don’t exist, so they do exist.”

Suppressed/neglected evidence

-fallacy of irrelevance/relevance

-ignoring evidence

-connects to confirmation bias

-might not have done research to provide all relevant evidence (can be unintentional)

-something relevant is missing

-Example: Selective reporting in journalism and media

lawyers do this too

begging the question (circular reasoning)

-assuming what you’re trying to prove

-can be seen through labels

-Example: Ghosts are real because I have seen one

Either/or Fallacy

-presents a false dilemma

-presents 2 options even though many exist

-could be presented as an if/then statement

-Example: You either make an A in the class or you fail

drawing the line fallacy

-exploits vagueness

-This fallacy says that because there is no clear boundary, there is no difference

-Example: there is no precise salary or income at which you become rich or poor, so there is no difference between the two

inconsistency fallacy

-hold incompatible beliefs

-contradict yourself

-Example: a parent telling their child not to smoke while smoking a cigarette