Flaw questions are the single most valuable question type to master in the Logical Reasoning sections — and there are now two scored LR sections on the current LSAT, so flaw skills touch a huge share of your score. Flaw questions appear frequently, and the skill they test (diagnosing exactly why an argument fails) is the same skill underlying Assumption, Strengthen, Weaken, and Parallel Flaw questions. Get flaws right and you lift a quarter of the whole test with you.

The trap most students fall into: they read the argument, decide the conclusion "seems wrong," and go hunting for an answer that feels critical. That's not the game. The game is precise. There is exactly one reasoning error the test wants, it has a name, and your job is to name it before you look at the answers.

What Flaw Questions Test

A flaw question hands you an argument that is definitely broken and asks you to describe how it's broken. The underlying skill is gap analysis: seeing the exact distance between what the premises establish and what the conclusion claims.

Here's the mental shift that changes everything. On a flaw question you are told, implicitly, that the argument is bad. So you don't waste energy evaluating whether the conclusion is true or reasonable. You assume it's unproven and ask a single question: what did this arguer do that a careful thinker wouldn't?

Every flawed argument makes an unjustified leap. The premises point one direction, the conclusion sprints past them. The flaw is the mechanism of that overreach — and the LSAT reuses the same mechanisms over and over. Once you can categorize them, flaw questions become pattern recognition rather than fresh reasoning each time.

How to Recognize Them

Flaw stems are among the easiest to spot. Look for these signals:

• "The reasoning in the argument is most vulnerable to criticism on the grounds that…"
• "The argument is flawed because it…"
• "The reasoning above is questionable in that…"
• "Which one of the following most accurately describes a flaw in the argument's reasoning?"
• "The argument is most susceptible to the objection that it…"

The moment you see "vulnerable to criticism" or "flaw," your brain should flip into diagnostic mode: find the conclusion, find the evidence, name the disconnect.

The Method

Run the same four steps every single time. Consistency is what makes this automatic under time pressure.

1. Find the conclusion first. Isolate exactly what the arguer is trying to prove. Bracket it. Everything else is either premise or noise.
2. Find the support. What evidence is offered for that conclusion? State it in plain terms.
3. Pre-phrase the gap. Before touching the answers, say out loud (or in your head) why the evidence doesn't get you to the conclusion. "They assumed X causes Y just because they happen together." "They surveyed one group and generalized to everyone." This is the whole game.
4. Match to a choice. Find the answer that describes your pre-phrased flaw in abstract terms. If you pre-phrased well, one choice will click.

Step 3 is non-negotiable. Students who skip pre-phrasing get seduced by wrong answers that sound logical-y. Students who pre-phrase walk in knowing what they're looking for and are immune to the traps.

The Common Traps

The LSAT recycles a compact roster of flaw types. Memorize these and you'll recognize most of what you see:

• Correlation vs. causation. Two things happen together, so the arguer claims one causes the other — ignoring reverse causation, coincidence, or a third factor. This is the single most tested flaw. Watch for it obsessively.
• Unrepresentative sample. The arguer draws a broad conclusion from a sample that's too small, self-selected, or biased.
• Part-to-whole (and whole-to-part). What's true of each part is assumed true of the whole, or vice versa. Each ingredient is cheap, therefore the meal is cheap.
• Equivocation / term shift. A key word changes meaning between premise and conclusion. "Natural" foods are healthy; arsenic is natural; therefore arsenic is healthy.
• False dichotomy. The arguer assumes only two options exist and rules out one, concluding the other — when a third possibility was available.
• Necessary vs. sufficient confusion. The arguer treats a necessary condition as if it were sufficient (or vice versa). If X is required for Y, that doesn't mean X guarantees Y.
• Ad hominem / source attack. The arguer rejects a claim by attacking the person who made it, not the claim itself.
• Circular reasoning. The conclusion is smuggled into the premises — the argument assumes what it's trying to prove.
• Appeal to authority / popularity. Something is true because an authority said so, or because many people believe it.
• Ignoring a possibility / overlooking an alternative. The broadest category — the arguer treats the evidence as if it forecloses possibilities it doesn't.

Now the two wrong-answer patterns that catch everyone:

The flaw that wasn't committed. The choice accurately describes a real flaw type — say, circular reasoning — but this particular argument didn't commit it. These are dangerous because the description sounds like textbook LSAT language. Test it: does this argument actually do that? If not, eliminate, no matter how tempting the vocabulary.

The accurate-but-not-a-flaw. The choice truthfully describes something the argument did, but that thing isn't actually a reasoning error. "The argument uses an example" — sure, it did, but using an example isn't a flaw. Don't reward a choice just for being true about the passage.

Also beware choices that criticize the conclusion for being false, or that demand the argument prove something it never claimed. Flaw answers describe reasoning errors, not disagreements with the outcome.

Worked Example

The following is an original question written in the LSAT style — not a real LSAC question.

Stem: Editorial: Ever since the city installed brighter streetlights downtown last year, the number of reported nighttime burglaries downtown has fallen by 30 percent. Clearly, brighter streetlights deter burglars. The city should therefore install brighter streetlights in every neighborhood to reduce burglary citywide.

The reasoning is most vulnerable to criticism on the grounds that it…

Let's run the method. Conclusion: the city should install brighter lights everywhere to cut burglary. Support: after lights were installed downtown, reported burglaries dropped 30%. Pre-phrase the gap: the arguer sees a drop happening after the lights and concludes the lights caused the drop — classic correlation-to-causation. Maybe police patrols increased downtown too. Maybe burglars moved to other neighborhoods. Maybe fewer burglaries were reported rather than fewer occurring. The evidence is downtown-only, but the conclusion is citywide.

The correct answer would read something like: "treats the mere fact that a decline in reported burglaries followed the installation of brighter lights as sufficient to establish that the lights caused the decline." That names the causal flaw precisely.

Watch how a trap would be phrased: "assumes that what is true of downtown must be true of every neighborhood" — this describes a real part-to-whole style gap, and it's tempting, but the deeper and more precisely tested error is the causal leap. When two answers both point at gaps, pick the one the argument depends on most directly. Here, everything rests on "the lights caused the drop."

A Few to Try

Work these the same way: conclusion, support, pre-phrase, match. Full explanations are in the practice set below.

How to Drill This Type

Flaw questions reward volume plus reflection. Here's how to actually get better:

• Build a flaw-type tally. Every flaw question you do, name the flaw type after you answer. Keep a running count. Within a few weeks you'll see that a handful of types (led by causation) dominate — and you'll recognize them instantly.
• Pre-phrase before every answer set. Cover the choices with your hand. Force yourself to articulate the flaw. If you can't, you don't understand the argument yet — reread it.
• Review your wrong answers by trap type. Were you fooled by a "flaw that wasn't committed" or an "accurate-but-not-a-flaw"? Log which trap gets you and it will stop getting you.
• Practice with real, official material. After you've built your foundation on original drills like the ones on this page, use official questions for the real thing. The authoritative source is LSAC's LawHub, which offers official PrepTests — that's where the real, format-current questions live. We don't reproduce LSAC's copyrighted questions here; our practice items are original Lovare questions built in the official style.

One last coaching note: speed on flaw questions comes from category fluency, not from reading faster. When you can slot an argument into "that's a causation flaw" in two seconds, you spend your remaining time confirming rather than searching. That's the difference between a 20-second flaw and a 90-second flaw — and across two LR sections, those seconds are your buffer for the hard questions.