Category Archive: Advice on Logical Reasoning

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Negate your way to LSAT dominance.

Let’s say I was trying to prove that every time you drink Fireball, you puke. If you wanted to prove the opposite, you’d have to find a way to show that there has not been a single instance in which you both consumed Fireball and vomited. Pretty tough, right? But let’s say that instead, you just wanted to show that it’s not true that you puke EVERY time you have Fireball. You’d just have to show me a single incident in which you had Fireball and didn’t vomit.

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Skip smart on LR.

With the February exam so painfully close – ack! – you should now be doing a whole lot of time-pressure practice. But just hurrying isn’t going to get you where you need to be. You have to hurry in a smart fashion.

When I was studying for the LSAT back before the wheel was invented (yes, the crusty psychometricians at LSAC are older than time itself, and so am I), I found myself hitting a ceiling. That ceiling was 168.

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Flaw Questions are the most common single question type on the LSAT. They also happen to be my favorite question type. I love pointing out people’s flaws, but people don’t always appreciate it. Like this one time, a guy at my house was about to say “glad,” but then changed it to “nice,” and it came out “glice.” I tried to point out the error, but somehow I was the bad guy?

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Last Minute Tips: Logical Reasoning

With less than three weeks until the June LSAT, it’s time to buckle down on studying. This week we’re offering one important last-minute tip for each LSAT section. In the last two days, we’ve looked at Reading Comprehension and Logic Games; today we’re talking Logical Reasoning.

The Logical Reasoning section of the LSAT can present an especially good opportunity to tweak your approach in the final weeks of prep. Why? Because many test-takers continually struggle with the same type of Logical Reasoning questions. It may be difficult to identify a pattern until you’ve taken a couple of practice exams, but once you have that practice under your belt, go back and look at all the questions you got wrong (or guessed correctly but didn’t know) on those tests.

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Mistaking the Necessary and Sufficient Conditions

A question on the Top Law Schools message board caught our eye this week:

Is there a difference between ‘mistaking the sufficient condition for the necessary condition’ and ‘mistaking the necessary condition for the sufficient condition’? I can sort of see a difference, but I feel like it could be phrased either way and still be the same flaw.

This is a great question.  As it turns out, the two things have slightly different meanings.  If you mistake the sufficient condition for the necessary condition, you treat the thing that really is the necessary condition as if it were the sufficient condition.  If you mistake the necessary condition for the sufficient condition, you treat the thing that really is the necessary condition as if it were the sufficient condition.

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Exclusivity Fallacies: Either You Read This Post or You Flunk the LSAT

You might’ve been here before: you’re trying to explain to your deluded Bay Area friends that Colin Kaepernick is not – and will never be – an elite quarterback.

“He throws when he should run. He runs when he should throw. He’s just plain dumb…”

Your friends are aghast, and they pull their trump card: Kaepernick had a 4.0 GPA in college, and scored phenomenally high on the Wonderlic Cognitive Ability Test before the NFL draft. Thus, they think they’ve established that you’re unequivocally wrong. And of course, they proclaim, that means they are right.


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Learn to Identify the Ad Hominem Fallacy, You Jerk

Everyone knows you should never take health instructions from an overweight doctor. Don’t go see the new Tom Cruise film — he’s a Scientologist. And never, but never, take lawn-upkeep advice from one of them Libertarians.

Each of these arguments rely on the same logical fallacy: Ad Hominem. They’re common, and if you’ve ever watched Glenn Beck you probably appreciate the need for their dismissal.

We have something of a tendency to allow these fallacies to corrupt our thinking in standard discourse — we may look less favorably on New York’s financial regulation after learning of Elliot Spitzer’s prostitution scandal, for example. Ultimately, however, arguments on the LSAT should be judged on their merit, not on the alleged character of the arguer.

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Reader Question: How to Drill LSAT Logical Reasoning

A blog reader writes: “Is it better to drill Logical Reasoning questions by type or do full, untimed sections?”

This is an incredibly important question.

Step 1: Learn The Method
Because there is a unique method for each LSAT Logical Reasoning question type, you need to focus on learning the steps and nuances of each individual method first. This takes time and a lot of careful practice: let’s say, about 50 questions worth of focused, perfect, and slow practice.

You should try to avoid doing questions for which you haven’t learned a method. If you just freestyle your way through Logical Reasoning, you’ll only develop bad habits, and bad habits are really hard to undo.

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Common LSAT Logical Fallacies: Composition

Have you ever heard that inane little riddle, “Which weighs more, a ton of bricks or a ton of feathers?” It’s gotta be bricks, they’re way heavier. Right?

The crux of this pissant’s play is the “ton,” of course; we’ve already established that their weights are equivalent. Thus, neither weighs more than the other. So why does anybody ever fall for something so silly?

We fall for it because we’re seduced by the Composition Fallacy. We believe, erroneously, that the things the ton is composed of has bearing on the weight of the whole. Such part-to-whole reasoning is not justified, for the same reason that you can’t make assumptions about a whole population based on the small subsection of people you’ve met.

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LSAT Logic Flaws: Correlation vs. Causation

Ever had this experience? Your gooberish buddy stumbles up to you, a couple drinks too deep, and spouts out an epiphany that (to him) rivals Einstein’s Annus Mirabilis. You and your LSAT-prepped mind, however, are not impressed. Something about the logic doesn’t sit right. It gives you an uneasy feeling deep in your gut — a sensation exacerbated by the PBR and stale pretzels sloshing around down there.

Let’s take an example. Say your friend — let’s call him Elliot — adamantly insists that when he stood up, Sexy Sadie looked over. He’s convinced that his standing caused her eyes to linger longingly on his portly physique and freshly-starched robin’s egg Polo.

You tell him, in accordance with your studies, that there are three methods by which we may seek to weaken a causal claim.