Definitions

Logical Fallacy: An error in reasoning that makes an argument invalid or unsound.

Argument: A set of statements where one (the conclusion) is supposed to follow from the others (the premises).

Valid Argument: An argument where if the premises are true, the conclusion must be true.

Sound Argument: A valid argument with true premises.

Appeal to Authority

Claiming something is true because an authority figure says it's true, without providing other evidence.

Example

"Einstein believed in God, so God must exist."

Why is this a fallacy?

Einstein was a brilliant physicist, but that doesn't make him an expert on theology or philosophy. His religious beliefs are not evidence for God's existence.

When It's Not a Fallacy

Appealing to authority is reasonable when:

  • The person is actually an expert in the relevant field
  • There's consensus among experts
  • The claim is within their area of expertise

Ad Hominem

Attacking the person making the argument instead of addressing the argument itself.

Example

"You can't trust what she says about climate change because she's a liberal."

Why is this a fallacy?

Someone's political views don't affect whether their scientific claims are true. The argument should be evaluated on its own merits, not the person making it.

When It's Not a Fallacy

Personal attacks can be relevant when:

  • Questioning someone's credibility as a witness
  • Pointing out conflicts of interest
  • Showing someone has a history of dishonesty

Straw Man

Misrepresenting someone's argument to make it easier to attack.

Example

Person A: "We should have stricter gun control laws."

Person B: "So you want to take away everyone's guns and leave us defenseless?"

Why is this a fallacy?

Person B is misrepresenting Person A's position. Stricter gun control doesn't necessarily mean taking away all guns or leaving people defenseless.

How to Avoid It

Always represent your opponent's argument in the strongest, most charitable way possible.

False Dilemma

Presenting only two options when there are actually more possibilities.

Example

"You're either with us or against us."

Why is this a fallacy?

There are many positions between complete agreement and complete opposition. Someone might agree with some points while disagreeing with others.

Common Forms
  • "Either X or Y" (when Z, W, etc. are also possible)
  • "If not X, then Y" (ignoring other alternatives)
  • "You must choose between A and B" (when C, D, E exist)

Slippery Slope

Arguing that one action will inevitably lead to a series of bad consequences, without showing why this chain of events is likely.

Example

"If we allow gay marriage, next people will want to marry their pets!"

Why is this a fallacy?

There's no logical connection between allowing same-sex marriage and allowing marriage to animals. The argument doesn't explain why one would lead to the other.

When It's Not a Fallacy

Slippery slope arguments can be valid when:

  • There's evidence that the chain of events is likely
  • The connections between steps are logical
  • Historical examples support the prediction

Conclusion

Logical fallacies are everywhere in everyday arguments, advertising, and political discourse. Learning to recognize them helps us think more clearly and avoid being misled.

The Key

Always ask: "Does this argument actually support the conclusion, or is it using a trick to make the conclusion seem more convincing than it really is?"