Each type of Logical Reasoning problem presents a unique challenge, and in order to have success on the Logical Reasoning section, it is essential to develop a strong understanding of the individual question types, as well as specific strategies that align with the different tasks that they present.
This infographic and article are here to help.
An infographic that lists and relates the different types of Logical Reasoning questions. Please click on the image to open fullscreen, print, or download.
(Includes: Identify the Flaw, Basic Assumption, Required Assumption, Strengthen the Argument, Weaken the Argument, Supporting Principle & Conform to Principle, Sufficient Assumption, Match the Flaw)
For all of the question types in this group, our task is to identify an argument in the stimulus, figure out why the support given is not enough to justify the point made, and then to address this problem in one way or another, per what is being asked of us in that specific question stem.
Identify the Flaw (6 - 10 per exam)
Identify the Flaw is the most common Logical Reasoning problem type, and these questions simply ask us to select the answer that most accurately represents the reasoning issue in the argument.
Basic Assumption (0 - 1 per exam)
These are very similar to Flaw problems, but instead of expressing the gap in the argument as a reasoning mistake, they represent it as an “assumption” made by the author.
Required Assumption (2 - 8 per exam)
Required Assumption questions, also commonly known as Necessary Assumption questions, ask us to identify the one answer that must be true in order for the argument itself to be valid. Note that the right answer does not have to “fix” the argument in any way—it is simply something that must be true in order for the argument to work at all.
An effective way to test whether an answer is indeed necessary is to try considering the opposite of it. If the opposite of the answer choice would destroy the reasoning in the argument, it’s a great sign that the answer choice is indeed something that is required for the argument to work.
Strengthen & Weaken (5 - 11 per exam)
Strengthen questions ask us to identify an answer that helps bridge the gap between the given point and the given support, and Weaken questions ask us to identify an answer that hurts connection or exposes a problem with it.
Keep in mind that Strengthen and Weaken question stems are written in terms of which answer “most strengthens” or “most weakens,” but for all such problems there will only be one answer that actually strengthens or one answer that actually weakens. Our task is never to see which of two answers strengthens more, or weakens more. Our task is to recognize why four answers simply do not perform the given task (most commonly because the wrong answer is not relevant to the given argument), and to find the one answer that does indeed strengthen or does weaken.
Supporting Principle & Conform to Principle (3 - 5 per exam)
These two types of principle questions are very similar. We can think of a principle as being a more general description of the reasoning structure that exists between the support and the conclusion in any given argument. Supporting Principle questions ask us to identify a general reasoning rule that would best justify the author’s reasoning, and Conform to a Principle questions ask us to identity the reasoning rule with which the given argument matches up best.
Sufficient Assumption (1 - 4 per exam)
Sufficient Assumption questions require us to identify one answer that would completely solve the reasoning issue that exists between the given conclusion and support. We want to look for that one right answer that will, when inserted into the argument, make it so that the support does indeed make the conclusion 100% valid.
Match the Flaw (1 - 2 per exam)
These problems require us to identify the answer choice that has the same reasoning issue as the original argument. Each of the five answers for these problems will themselves have arguments, with conclusion and support that must be evaluated, and so you should expect for these problems to take a little bit longer to solve than others.
(Includes: Method of Reasoning, Identify the Conclusion, Identify the Role, Match the Reasoning)
These problems are very similar to those in Group One except for one major difference: for these problems, our job is not to evaluate the validity of the reasoning. We are not being asked to think about why the reasoning is flawed, and doing so can be an unnecessary distraction.
These problems are great indicators of your ability to read for reasoning structure. If you are a great reader, you will find these to be, on average, some of the easiest questions in the section. If you are struggling with the questions in this group, chances are that making improvements here will have a positive effect on how you perform on other types of problems as well.
Method of Reasoning (0-2 per exam)
Method of Reasoning questions ask us to identify the answer that most accurately represents the support-conclusion relationship presented in the stimulus. Some arguments will combine two premises to reach a conclusion (Tom likes rice and Tom likes beans so he should like rice and beans), others link one premise to another to reach a conclusion (All mice are happy animals and all happy animals smile therefore all mice smile), some arguments contain conditional reasoning that deals in absolute truths (such as a conclusion that states “All tenants must sign the new agreement”) while others reach a conclusion about cause and effect (“Since Jill was driving, she must have caused the accident”), and the list of descriptives goes on and on. The right answer will accurately describe the given argument, and the wrong ones will misrepresent it.
Identify the Conclusion (1 -3 per exam)
For these problems, our job is to correctly identify the author’s main point in the given argument. It’s important to be careful not to over-infer—our job is not to come up with our own conclusion, but rather to find the answer that best represents the conclusion given to us in the text.
Identify the Role (0 - 4 per exam)
For these problems, we are asked to identify the role that is played by a particular part of the given stimulus. The role will relate to the structure of the included argument: the point made, support, opposition, or background.
Match the Reasoning (0 - 2 per exam)
Match the Reasoning questions require us to first identify the method of reasoning (as we did for Method of Reasoning questions) then identify an answer choice that most similarly matches that reasoning structure. Just as with Match the Flaw problems, we should expect to spend a bit more time on Match the Reasoning problems, for they require a few extra layers of work from us.
(Includes: Inference, Explain this, Identify the Disagreement, Give an Example)
Finally, there are a minority of questions that are not defined by arguments.
Inference (5 - 9 per exam)
This is a very common question type and perhaps deserves a group all for itself. Inference questions ask us to find the one answer that is supported by the information given in the stimulus.
The “level of provability” depends on the exact wording of the question stem. A question that asks you to find an answer that “must be true” will allow for less flexibility than one that asks for an answer that is “most supported.”
The inference made in the right answer can be derived from an individual piece of information given in the stimulus, or it can be derived by combining various parts of the stimulus together. It’s important to note that typically the right answer does not have to be a “main point” of the given stimulus—any answer that is justifiable based on the given information will be correct. On a related note, because there are numerous inferences that can be made off of any given stimulus, the right answers to these questions are not predictable.
Thus Inference questions, even more than others, require us to utilize our elimination skills. The most absolute thing about many of these Inference problems, especially the hardest ones, is that the wrong answers are clearly not justifiable based on the given text. Right answers are often very difficult to prove and will sometimes leave you feeling a bit wishy-washy, but wrong answers are almost always clearly, absolutely, and obviously wrong.
Explain This (2 - 5 per exam)
Explain This problems (a.k.a. “Explain a Discrepancy”) will present you with two pieces of information that seemingly don’t go together (for example, “Fred is very handsome, but no one will ever kiss him.”), and our job is to pick an answer that provides the most plausible explanation (for example, “Fred’s breath is so back people can’t get within a foot of him.”)
A great way to approach these problems is by asking, “How come?” as in “How come no one will kiss Fred even though he is handsome?” Only one of the five choices will provide a plausible explanation.
Identify the Disagreement (0 - 2 per exam)
For these questions, we will be given brief statements by two different individuals, then asked to find the answer that best represents what the two people disagree about.
It’s important to note and remember that these two people are commonly not on the same page—the first person is thinking about one thing and the second person another—there is just a small area of overlap between the two statements, and it is in this overlap that you will find the disagreement.
The most tempting wrong answers for these problems give information about which one person has a very strong opinion, but the other person does not. You want to verify your answer to an Identify the Disagreement problem by making sure that each person does indeed have an opinion about the information in a particular answer choice, and that, of course, these opinions contrast.
Give an Example (0 - 3 per exam)
These problems are essentially the mirror twins of “Conform to a Principle” questions. For “Conform to a Principle” problems, we needed to find a principle with which the situation in the scenario fits. For “Give an Example” questions, we are given a principle in the stimulus, then asked to identify among the answer choices a situation that best fits that principle. The skills you’ve developed in order to master other question types should fairly easily translate to the challenges of this question type.
Mike Kim is the author of The LSAT Trainer, the most popular and acclaimed new LSAT learning study guide to be released in over a decade. Previously, he co-created the curriculum for ManhattanLSAT. Inspired by self-study students who prepare for the exam on their own, Mike set out to write the ultimate self-study guide, and The LSAT Trainer is the result.