Articles published in Logical Reasoning

The Morbid Flaws


Some people have trouble with flaw questions on the LSAT because there are two ways the answer choices can be worded. One just points out the assumption by asking what the argument “takes for granted.” The other points out the assumption, too, but in a more indirect way; it tells you something the argument isn’t considering by making the assumption:

The argument fails to consider that…


The argument ignores the possibility that…

When I teach flaw questions, there are a couple of morbid examples I like to use to illustrate the difference. So apologies in advance for being a Debbie Downer, but I like to think the morbidity of these makes them more memorable. Here they are, the Morbid Flaws. Read more

The Necessary Alarm Clock


The terms “necessary” and “sufficient” get thrown around a lot in the LSAT world these days. We at Manhattan LSAT use them to distinguish between two different kinds of assumption questions. They come up on the test in answer choices (for example, “The argument mistakes a necessary condition for a sufficient condition”). And usually by the fourth session of a course, students start making jokes like, “I had half a sandwich earlier, which was necessary, but not sufficient.” We all pretend not to love the joke.

But what do they mean? One of my favorite analogies for explaining the basic difference between necessary and sufficient is the alarm clock. We’ll call it the Necessary Alarm Clock.

alarm clock

Say I have a very hard time waking up. I’m a sad, awful person who hates morning, sunlight, and everything to do with happiness. I so dread being awake, in fact, that in order for me to get up in the morning, eight things need to happen:

1. My alarm clock goes off.
2. The smell of bacon drifts into my room.
3. I have dreamt of lilies and puppies.
4. Speaking of puppies, my dog is licking my face.
5. A marching band passes.
6. It’s not a Monday.
7. I am not hungover.
8. It is 72 degrees in my bedroom.

Again, in order to wake up, every single one of these things must occur.

So what is sufficient for me to wake up? 1-4? 5-8? 1, only? None of these. The occurrence of 1-8 is sufficient for me to wake up, and 1-8 only. Could we say, then, that 1-8 is also necessary for me to wake up? Sure! Each of these has to happen; that means they are all necessary.

How about my alarm clock going off? Is that sufficient for me to drag my caboose outta bed? No. 2-8 still has to occur. But is it necessary? To answer that question, we ask what would happen if it DIDN’T go off. If it didn’t go off, I’m still snoozing. So, yes, it’s necessary.

Finally, suppose 1-8 occurred, plus there were fourteen cheerleaders practicing in my kitchen. Would I wake up? Of course I would. The sum total of 1-8 plus the cheerleaders is sufficient to get me out of bed. But is the sum total of 1-8 plus the cheerleaders necessary to get me out of bed? No. The cheerleaders can be disposed of.

Yes, I wrote this post just to be able to close with that sentence.

Logical Reasoning And Rick Santorum


Rick Santorum

Rick Santorum sure has made some controversial remarks lately. But are they logically sound? Regardless of your political leaning, it pays to know how to evaluate the pieces and soundness of an argument. For this week’s post, I’ve plucked a few Santorum gems to help you review logical reasoning strategy. Can you identify the question types, below? Better yet, can you answer them? Answers after the jump! Read more

One of the Hardest LSAT Questions – @!#$%@# Dioxin!


Like snowflakes of intellectual pain, the hardest LSAT question is different for each and every one of us – it’s up to us to look into our hearts and find the question that is burning a hole through an artery. For me, that was PT45, S1, Q12 – the dioxin question. Oh how we fought, oh how we struggled!

Let me walk you through our relationship.

The conclusion of the argument is that, as opposed to what most people are thinking, dioxin released from a mill does NOT cause fish to have abnormal hormone levels. Why? Two premises are given to support this – and here’s where we had our first fight L: dioxin decomposes quite slowly and when the mill shuts down, the fishy hormone levels quickly return to normal.

At this point, me and question 12 were still on speaking terms, but when I looked at her answer choices, oh the pain! The correct answer – the one that most weakens the argument – states that dioxin actually is washed away pretty quickly from the mill area. Sounds painless enough – until you think about it! How does that weaken that argument? I was lost. Read more

LSAT Vocabulary



I just saw a good blog post listing vocabulary words that you should have under your belt for the LSAT.   Take a look and see if you really know all of them.  Thanks for the list, Steve!

LSAT Weaken Questions – Logical Reasoning


Weaken questions can operate in a few different ways. Let’s look at some examples.

Sep 09 Exam, Section 4, #2

Here’s the basic logic given in the argument:

You can always keep your hands warm by putting on extra layers of clothing (clothing that keeps the vital organs warm).

THUS, to keep your hands warm in the winter, you never need gloves or mittens.

This argument is a sound argument – no flaws or assumptions. If you have another option for keeping your hands warm, then you never truly need gloves or mittens.

In this case, the correct answer actually attacks the main premise. The correct answer says that sometimes (when it’s really really cold) putting extra layers of clothing on actually is not enough to keep your hands warm. Notice how this contradicts the premise. So, to weaken an argument you can attack a supporting premise.

Read more