LSAT Logical Reasoning Flaws, Fallacies List

LSAT Logical Reasoning questions often hide a classic logical fallacy inside stimulus language specific to that argument's topic, rather than naming the flaw outright. This page lists the fallacies that show up most, from false cause and appeal to authority to ambiguity and the false binary, each with real LSAT question citations so you can see the pattern in context.

I walk through the most common flaw patterns in the video below.

The LSAT Logical Reasoning section tests your ability to spot a variety of flaws. Some are as simple as failing to consider a particular possibility, but we can group the others into the category of classic logical fallacies. They’re the type you find in basic logic textbooks.

Many Logical Reasoning questions describe flaws in the abstract, but most speak in terms of the stimulus topic. They’ll say things like: “the argument fails to consider…(something specific to the topic of that argument).” However, even when the stimulus talks in terms related to that argument, it often refers to a classic flaw.

Download my free Common LSAT Flaws PDF here

It’s useful to be familiar with such flaws so that you recognize them when they appear, even if the language is in terms of the argument, rather than in the abstract.

Two great websites, Your Logical Fallacy Is and Information is Beautiful, provide basic, well-designed overviews of common logical fallacies. Obviously, neither site is tailored to the LSAT in particular, but beginners may find them helpful.

The guy who made Your Logical Fallacy Is provides funny examples of each fallacy, and all the content is also in one place, infographic-style.

The folks behind Information is Beautiful also posted the same info in a Google Doc, so you can get all their “Rhetological Fallacies” info in one place.

Below, I list each of the fallacies covered by these sites, along with a brief description of each, and provide an example or two (or more) of an actual LSAT question exhibiting that flaw:

(page numbers are for the newest edition of the relevant LSAT PrepTest book – usually Next 10)

Common LSAT logical fallacies, with real question examples

1. False Cause (Correlation / Causation)

presuming that a real or perceived relationship between things means that one is the cause of the other

• PrepTest 30 (December 1999 LSAT), S2, Q25 (p61)
• PrepTest 37 (June 2002 LSAT), S4, Q17 (p312)

2. Appeal to Emotion

attempting to manipulate an emotional response in place of a valid or compelling argument

• PrepTest 26 (September 1998 LSAT), S2, Q1 (p258)

3. The Fallacy Fallacy

presuming that because a claim has been poorly argued, or a fallacy has been made, that it is necessarily wrong

• PrepTest 31 (June 2000 LSAT), S3, Q23 (p102)
• PrepTest 37 (June 2002 LSAT), S2, Q21 (p301)
• PrepTest 38 (October 2002 LSAT), S1, Q23 (p329)

4. Ad Hominem (Personal Attack)

attacking the opponent’s character or personal traits instead of engaging with their argument

• PrepTest 19 (June 1996 LSAT), S2, Q14 (p24)
• PrepTest 25 (June 1998 LSAT), S4, Q4 (p241)
• PrepTest 32 (October 2000 LSAT), S4, Q6 (p139)
• PrepTest 34 (June 2001 LSAT), S2, Q1 (p194)
• PrepTest 38 (October 2002 LSAT), S1, Q8 (p323)
• PrepTest 38 (October 2002 LSAT), S4, Q8 (p344)

5. Burden of Proof

saying that the burden of proof lies not with the person making the claim, but with someone else to disprove

• PrepTest 35 (October 2001 LSAT), S4, Q7 (p242)

6. Ambiguity (Equivocation)

using a double meaning or ambiguity of language to mislead or misrepresent the truth

• PrepTest 34 (June 2001 LSAT), S3, Q12

7. The Gambler’s Fallacy

assuming that “runs” occur to statistically independent phenomena such as roulette wheel spins

• PrepTest 33 (December 2000), S1, Q24 (159)

8. Bandwagon

appealing to popularity or the fact that many people do something as an attempted form of validation

• PrepTest 28 (June 1999 LSAT), S1, Q9 (p324)
• PrepTest 28 (June 1999 LSAT), S1, Q19 (p327)
• PrepTest 32 (October 2000 LSAT), S4, Q13 (p141)

9. Appeal to Authority

using the opinion or position of an authority figure, or institution of authority, in place of an actual argument

• PrepTest 20 (October 1996 LSAT), S4, Q20 (p75)
• June 2007 LSAT, S2, Q17

10. Composition Division (Part-to-Whole)

assuming that one part of something has to be applied to all, or other, parts of it

• PrepTest 19 (June 1996 LSAT), S4, Q3 (p36)
• PrepTest 31 (June 2000 LSAT), S3, Q18 (p100)
• PrepTest 35 (October 2001 LSAT), S4, Q18 (p245)

11. Genetic

judging something as either good or bad on the basis of where it comes from, or from whom it came

• PrepTest 30 (December 1999 LSAT), S2, Q26 (p61)

12. Black or White (False Binary/Dilemma)

presenting two alternative states as the only possibilities, when in fact more possibilities exist

• PrepTest 35 (October 2001 LSAT), S4, Q13 (p243)
• PrepTest 38 (October 2002 LSAT), S1, Q11 (p325)

13. Begging the Question (Circular Reasoning)

presenting a circular argument in which the conclusion was included in the premise

• PrepTest 36 (December 2001 LSAT), S1, Q10 (p257)

14. Middle Ground

claiming that a compromise, or middle point, between two extremes must be the truth

• June 2007 LSAT, S2, Q2

Flaws I haven’t found LSAT examples for yet

I didn’t provide examples of the following flaws in actual LSAT questions simply because none came to mind. (This doesn’t necessarily mean they don’t exist on the exam, though.)

If you find an example of an LSAT question exhibiting one of the following flaws, please let me know, and I’ll add it to the list above.

15. The Slippery Slope

suggesting that if we allow A to happen, then Z will eventually happen too, therefore A should not happen

16. Straw Man

misrepresenting someone’s argument to make it easier to attack

17. Tu quoque

avoiding engagement with criticism by turning it back on the accuser – answering criticism with criticism.

18. Personal Incredulity

assuming that because you found something difficult to understand, or are unaware of how it works, it’s probably not true

19. Special Pleading

moving the goalposts or making up an exception when a claim is shown to be false

20. Loaded Question

asking a question that had an assumption built into it so that it couldn’t be answered without appearing a particular way

21. No True Scotsman

appealing to purity as a way to dismiss relevant criticisms or flaws of an argument

22. Appeal to Nature

arguing that because something is ‘natural’ it is therefore valid, justified, inevitable, or ideal

23. Anecdotal

using a personal experience or an isolated example instead of a sound argument or compelling evidence

24. The Texas Sharpshooter

cherry-picking a data cluster to suit the argument, or finding a pattern to fit a presumption

Frequently asked questions

What are the most common LSAT logical reasoning flaws?

False cause, appeal to emotion, the fallacy fallacy, ad hominem, burden of proof, ambiguity, the gambler's fallacy, bandwagon, appeal to authority, composition/division, the genetic fallacy, false binary, and begging the question all appear on real LSAT questions, cited by PrepTest and question number on this page. Half the battle is language, so pair this with the LSAT Logical Reasoning vocabulary list.

What is false cause on the LSAT?

Presuming that a real or perceived relationship between two things means one causes the other. It appears on PrepTest 30, Section 2, Question 25, and PrepTest 37, Section 4, Question 17. Spotting the flaw is also step 1 of solving Strengthen questions.

Where can I find a free list of LSAT flaws?

This page links a free downloadable Common LSAT Flaws PDF, plus a full breakdown of each fallacy with real LSAT question examples so you can see how each one shows up on the actual test. To practice on the hard ones, use my list of difficult LSAT Logical Reasoning questions.

Related: see the flaw types worked in real questions in the free full-text explanations for PrepTest 159, with more PrepTests added weekly.

Watch a related lesson

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