General Guide to Logical Reasoning
This guide will teach you how to approach logical reasoning questions, and the section as a whole. It contains general strategy that is universal to all logical reasoning questions, and won’t go into individual question types (for a detailed breakthrough of all question types once you’re done reading this, click here).
Logical Reasoning makes up 2 out of the 4 sections that will count towards your LSAT score, so in that sense, it’s the most important section to do well on. It’s also a middle point in terms of skill set between the “raw logic” of Logic Games and the strong verbal emphasis of Reading Comprehension. If you can be super confident on this section, chances are you’ll be in pretty decent shape for the entire test.
The section is made up of 24-26 short questions which you ultimately must finish in 35 minutes, which means you’ll have a little under a minute and a half (on average) for each question. Each question will present a paragraph followed by a short multiple-choice question pertaining to the paragraph. (On earlier tests, sometime 2 or 3 questions will refer back to the same paragraph.)
The questions start off relatively easy and get trickier as you progress in the section, usually with a few Olympically difficult questions towards the end.
There’s a very simple set of steps you should follow on every Logical Reasoning question. In order to illustrate them, I’ll be using an example from the free June 2007 LSAT, so if you haven’t taken that test yet, come back and read this once you have so you don’t spoil the question (or just skip over the example parts of this guide).
- Read the question first
Again, every question will have a paragraph of text, followed by a one-sentence question. Even though the paragraph is written first, train yourself to jump ahead and read the question first. This is unequivocally more efficient, and perhaps one of the places where conventional LSAT wisdom is in agreement with MasterLSAT (gasp).
The reason is because if you read the question first, you’ll know what you’re looking for as you’re reading the paragraph. Is the question asking you to find a flaw in the argument? The main conclusion? A missing assumption? Instead of first reading the paragraph, not knowing what you’re looking for, and only then reading the question, and then having to check back to the paragraph, why not save time and read the question first?
So, in the following question from June 2007…
…your eyes would jump straight down to “Which one of the following, if true, would count as evidence against the scientist’s explanation of Earth’s warming?” first.
So now, you know you’re about to read an argument (a scientist’s argument for why the Earth warmed) that you will be trying to WEAKEN. Which brings us to step #2:
- Read the paragraph, and simultaneously think ahead to try to predict the answer
You can train your mind to be in two places at once. As you’re reading and digesting the information in the paragraph, you want to be thinking ahead to some things that could potentially answer the question. It’s not something you want to spend extra time on, but it helps a lot to be thinking ahead as you’re reading the paragraph.
For example, in the question above, as you’re reading the scientist’s argument, you should already be thinking about some things that would weaken it. The scientist is arguing that the global temperature growth over the past century was “primarily the result of the buildup of minor gases in the atmosphere, blocking the outward flow of heat from the planet”. (Note: the scientist isn’t arguing that warming occurred – that is taken for granted by the argument. What he/she is arguing is the reason why the warming occurred. It’s important to always hone in on exactly what is being argued.)
The scientist is arguing that the gas buildup caused the warming. So, you know that the answer will be anything that makes it less likely that the gas buildup caused the warming. And so, your goal is to try to think of a couple of possible things that would make it less likely that the gas buildup caused the warming, as you’re reading the paragraph.
It could be that, even though gas buildup does block the outward flow of heat, perhaps not in a way that would change the global temperature. Maybe those gases keep the heat high up in the atmosphere, and the global temperature is measured at the Earth’s surface. Or maybe the gases only block very minimal amounts of heat that couldn’t have affected the global temperature as much as 0.5 degrees Celsius. Or, maybe something else happened over the last century that was more likely to be the culprit responsible for the temperature increase, like a meteor, or an orbit variation, or an excessive number of volcano eruptions, which means it was probably that, and not the gas buildup, that caused the warming.
The point is just to get your creative mind thinking critically about potential right answers. Try to predict roughly what the answer will be. And then, you’ll be much more likely to spot it when you see it.
(Note: For a more advanced breakdown of disproving causal arguments, including a detailed analysis of this exact question and how to be more methodical about this step, click here.)
Try to think as generally as possible about things that would weaken the argument. That way, you’re more likely to encompass what the answer will eventually be. Whatever you can come up with as you’re reading the paragraph for potential answers, keep them in mind and then look for something similar in the answers.
(It’s worth noting here, as an aside, that whatever the right answer is, it can’t contradict with any facts given in the paragraph. For example, notice how I didn’t suggest that a right answer might be “No, you’re wrong Scientist, minor gases don’t block the outward flow of heat!” We have to take for granted that the scientist isn’t lying, and just prove that despite that, the conclusion that the scientist is arguing based off of his facts is not necessarily true. The good news is that none of the wrong answers will ever contradict with the paragraph either, so you don’t have to worry too much about this.)
You’d be surprised, once you get good at this, how often you’ll know the right answer without even having read it. It takes training, but even if you are way off at first, it’s like shooting arrows – even though you’ll be missing the target at first, by attempting it, you’ll be honing your skills and more likely to get closer the next time. Often, in going over LR questions with my students that they found very tough, I’ll read the paragraph and tell them what the answer is likely to be, and to their amazement I’ll hit it dead on – and I’m always happy to break down my logic for exactly how I made that prediction. It’s something that comes with practice, but imagine if you could predict every answer on the LSAT – it would make the test a piece of cake.
So, to recap:
- try to predict the answer as you read the paragraph
- try to be as general as possible so you can encompass all potential answers
- you will improve at this over time
OK, so now that you’ve read the question and the paragraph, and you have some ideas for what you’re looking for in the answers…
- Read through all 5 answers and look for an easy answer
Look for a “bingo” answer – something that matches exactly what you’re looking for. The earlier on you are in the section, you more likely you are to spot the answer easily when you see it. Many answers on this section will be obvious, especially if you’ve already thought ahead to potential answers, so don’t be afraid of an easy answer.
The bottom line here is that you should be holding out for an easy answer. Don’t spend more than a few seconds reading and analyzing each answer choice. After spending those few seconds reading an answer, three things are possible:
- You’re sure it’s wrong. If so, cross it out.
- You’re sure it’s right. If so, circle it (but continue to read and consider all 5 in case you made a mistake).
- You’re unsure, and it will take 10-20+ more seconds of analysis to think through whether this answer is right or wrong. Don’t spend those 10-20 seconds now. Keep going – the next answer might be obviously right in which case you can save all that time!
It’s important to at least read and consider all 5 answers, on every single question. The authors of the LSAT are very, very skilled at writing trick answers (God bless them) and there will certainly be wrong answers that seem to clearly be right answers. Let’s say (B) and (E) both look good – between the two of them, the trick answer is just as likely to be (B) as it is to be (E), which is why it’s super important to keep an open mind and honestly consider each answer choice as you go down the list.
OK, so back to our example question:
If you’re thinking ahead and potentially looking for something that proves that the gas buildup could not have caused the warming, you might spot that in (B) right away! (B) makes it impossible that the gas buildup was the primary cause of the warming. If the warming happened before 1940, and the gas buildup happened mostly after that, then how could the gas buildup be what caused the warming? X can’t be the cause of Y if Y happened before X. Bingo.
(Note that the year didn’t have to be 1940. It could have been 1941, 1942, 1999, 1907 – and still would have had to be the right answer. As long as Y happened before X, it’s impossible that X caused Y, no matter the particulars of when they happened. You’re just looking for something that if true, would have to weaken the argument.)
OK, great! You found the answer. Or did you?
What if, by doing step 3, you didn’t find any easy answers? Or, what if you found two easy answers?
If you found anything other than one easy answer, then move onto step #4.
- (If you don’t already have the answer from step #3) Do a more detailed analysis of the answers remaining
This is your second, more detailed pass through the answers, if need be. You may have crossed some answers off as definitely wrong – great. Whichever ones are left standing as potentially right, read through again more carefully. This is your chance to do that more detailed analysis you were hoping to skip in step #3! This will happen a lot, but the point is that you saved yourself that time on the many other questions on which there is a simple right answer.
In our example question, (C) is a trick answer commonly picked. Let’s say you have it narrowed down to (B) and (C) by the time you get to this step.
Think carefully about each one. (C) is saying that the solar radiation wasn’t constant throughout the century – it was greater in some years, and lesser in other years. Would this make it less likely that the gas buildup was the cause of the global warming?
No! Regardless of whether there was a steady stream of radiation, or whether it was greater in some years than others, the temperature increase could still just as easily been due to gas buildup. If (C) said “Over the last century, Earth received slightly more solar radiation than it had in the past century”, then this could arguably show an alternative cause for the warming (greater solar radiation!). But it doesn’t say that; it says that there was more radiation in some years of the century than in other years of the same century. This wouldn’t explain why this century got warmer than the previous century. I’m convinced that most people pick (C) on this question because they read it too quickly and misinterpret it as saying the above.
This is the kind of mistake that you can catch upon close reading in step #4!
Repeat step #4 as necessary until you have one definitely right answer. If you’ve crossed all 5 answers out – that means you definitely misinterpreted something, but don’t sweat – time to go back and revisit each one more carefully.
Voila! Congrats on finishing a logical reasoning question. Time to do 25 more…
General section tips:
- If you get to an impossibly tough question (they exist) and you’re having trouble, skip it and come back later. There’s nothing to gain from continuing to hit your head against the wall once you realize that you’re hitting your head against the wall. The confidence and rhythm of answering a few other questions could be all it takes to clear your mind for when you return to it.
- There is a clear answer for each question. I know that sometimes it feels like “you can make an argument for (A) and also for (C)”, but the truth is: no, one is right and one is wrong, and it’s your job to figure out exactly why. If you read them carefully enough, you’ll see what your error was. Go for the point of clarity on every question, when you can confidently circle one answer and be sure that none of the others are correct. It could take you extra time, but don’t worry about the time limit just yet.
- I can’t stress enough the importance of not getting married to an early answer choice that seems correct before reading the others, especially later on in the section when they are really throwing everything they’ve got at you in the way of trick answers. You have an emotional bias: if your original instinct was right and (A) is correct, then you won’t have to spend all that time reevaluating it. You must fight against this emotional bias and honestly give each answer choice its “day in court”, so to speak, even if you already think it’s (A).
So, there you have it. A general guide that will work for every single Logical Reasoning question you can possibly find. Time to get practicing.
Oh, and if you haven’t already, download your Free MasterLSAT Study Guide which will tell you exactly what you need to do to reach a 99th-percentile score on the LSAT.