Flaw and Logical Fallacy Questions

LSAT Logical Reasoning Prep

Assuming that because X guarantees Y, that X is required for Y (or that because Y is required for X, that Y guarantees X)

Confusing necessary and sufficient conditions

Assuming that because X and Y are associated with each other, X must cause Y

Assuming correlation proves causation

Citing to the costs of something without considering the benefits (or vice versa)

Overlooking costs/benefits

Assuming that what’s true about the individual parts of X must also be true about X (or vice versa)

Confusing part v. whole

Drawing conclusions about a group based on a sample that we have reason to think is meaningfully different from the group

Unrepresentative samples

Drawing broad conclusions from too little evidence

Hasty generalization

Assuming that because X and Y are similar in one respect, they must be similar in another respect

Analogies that aren’t analogous enough

Assuming only two options exist (or that the available options are mutually exclusive)

False dichotomy

Attacking the person/group making the argument instead of the argument itself

Attacking the source of the argument (ad hominem)

Assuming that the proportion of something proves the amount of the thing (or vice versa)

Percentages v. amounts

Assuming a conclusion is false simply because the argument in support of that conclusion is weak (or assuming that because something hasn’t been proven true, that it must be false)

Lack of support vs. false conclusion

Assuming a relative relationship proves an absolute quality (or vice versa)

Relative v. absolute

Using the same term in two different ways without acknowledging the shift in meaning

Equivocation

Relying on an expert in one field to support a conclusion concerning a different field

Appealing to authority in an area outside their expertise

Presenting a conclusion that is simply a restatement of a premise

Circular Reasoning

Deriving conclusions that assume value judgments based on premises that are only factual

Confusing is for ought

Assuming that because people believe X, that X is true (or that because X is true, people must believe or be aware of X)

Belief v. facts

Assuming that because something is possible that it’s probable/certain (or that because something is probable, it is certain)

Confusing possibility, probability, and certainty

The professor might dislike me, because I don’t share her political opinions. So, the professor dislikes me.

Confusing possibility, probability, and certainty

Most people believe the violent crime rate has increased this year. So, the government needs to do something about this increased violent crime rate.

Belief v. facts

Historically, humans have always fought wars. Therefore, military conflict is an acceptable way to resolve international disputes.

Confusing is for ought

Everything the holy book says must be true. Why? Because the holy book can’t say anything false.

Circular Reasoning

Tom Brady, one of the greatest NFL quarterbacks ever, says we should invest heavily in cryptocurrency. So, let’s buy some cryptocurrency.

Appeal to authority

Our company needs a strong leader. Sarah has proven she's a strong person - she runs marathons and does CrossFit. Therefore, Sarah should be our next CEO.

Equivocation

I got a higher grade in my algebra class this year than I got last year. Thus, I got a high grade in algebra this year.

Relative v. Absolute

Some people say the new advertising campaign will succeed because it appeals to today’s youth. But today’s youth will find the campaign lame and unappealing. So, the advertising campaign will not be successful.

Lack of support vs. false conclusion

Tacos made up 80% of my restaurant’s sales this year, whereas last year tacos made up only 50%. So, this year my restaurant sold more tacos than last year.

Percentages v. amounts

Don't listen to Dr. Smith's research on climate change - he drives a gas-guzzling SUV!

Ad Hominem

Since you don't support banning all guns, you must support unrestricted gun ownership.

False dichotomy/ dilemma

A computer and a human brain both process information using electrical signals. When a computer malfunctions, restarting it often fixes the problem. Therefore, using electroshock therapy should effectively treat many mental health conditions.

Analogies that aren’t analogous enough

I got food poisoning from a sushi stall at the Cincinnati airport. So, we should generally be prepared to get food poisoning when eating sushi.

Hasty generalization

I polled people leaving a yoga studio about their exercise habits, and everyone indicated they exercise at least 5 times per week. Therefore, the average American exercises 5 times per week.

Unrepresentative samples

Since each individual cell in my body is invisible to the naked eye, my entire body must be invisible too. Our university is ranked #1 in research, so every professor here must be a top researcher.

Confusing part v. whole

This new law requiring companies to reduce carbon emissions should be rejected because it will cost businesses money to implement.

Overlooking costs/benefits

People who eat healthy diets tend to get more exercise than people who eat regular diets. Thus, one’s diet can impact how much one exercises.

Assuming correlation proves causation

If it’s raining, the ground is wet. We know the ground is wet. So, it must be raining.

Confusing necessary and sufficient conditions