LSAT Logical Reasoning

Primary Objective #1

Determine whether the stimulus contains an argument of if it is only a set of factual statements.

Primary Objective #2

If the stimulus contains an argument, identify the conclusion of the argument. If the stimulus contains a fact set, examine each fact.

Primary Objective #3

If the stimulus contains an argument, determine whether the argument is strong or weak.

Primary Objective #4

Read closely and know precisely what the author said. Do not generalize!

Primary Objective #5

Carefully read and identify the question stem. Do not assume that certain words are automatically associated with certain question types.

Primary Objective #6

Prephrase: after reading the question stem, take a moment to mentally formulate your answer to the question stem.

Primary Objective #7

Always read each of the five answer choices.

Primary Objective #8

Separate the answer choices into contenders and answers. After completing the process, review the contenders and decide which answer is the correct one.

Primary Objective #9

If all five answer choices appear to be losers, return to the stimulus and re-evaluate the argument.

Premise

A fact, proposition, or statement from which a conclusion is made.

Conclusion

A statement or judgement that follows from one or more reasons.

Premise Indicators

because, since, for, for example, for the reason that, as indicated by, due to, owing to, this can be seen from, we know this by, in that, & given that

Conclusion Indicators

thus, therefore, hence, consequently, as a result, so, accordingly, clearly, must be that, shows that, conclude that, follows that, & for this reason

Additional Premise Indicators

furthermore, moreover, besides, in addition, what’s more, & after all

Counter-Premise Indicators

but, yet, however, on the other hand, admittedly, in contrast, although, even though, still, whereas, in spite of, despite, & after all

Reference Words (list)

this/that/these/those, it, they/their/them, one/ones, former/latter

Quantity Indicators

all, every, most, many, some, several, few, sole, only, not all, & none

Probability Indicators

must, will, always, not always, probably, likely, would, not necessarily, could, rarely, & never

True or False: Premise and conclusions can be presented in any order

True

If a conclusion is present, what should be done?

You MUST identify the conclusion and then proceed on to the question stem.

True or False: A fact set can contain a conclusion.

False: Only arguments contain conclusions.

Counter-Premises

Bring up points of opposition or comparison.

Simple Arguments

Contain a single conclusion

Complex Arguments

Contain more than one conclusion

Reference Words (def)

Words that refer back or forward to ideas in the stimulus without explicitly naming the idea.

Upon identifying an isolated reference word, what should be done?

Ensure that you know what the isolated reference word is referring to.

Truth vs Validity

Truth = Does it happen as stated in the real world?

Validity = Does the conclusion follow logically from a set of given premises?

Inference

Probably true or likely to be true (MUST BE TRUE).

Assumption

(In argumentation) It is simply an unstated premise.

Question Type: Must be true

Asks you to identify the answer choice that is best proven by the information in the stimulus.

Question Type: Main point

Asks you to find the primary conclusion made by the author.

Question Type: Point at issue/point of agreement

Requires you to identify a point of contention between two speakers/requires you to identify a point of agreement between two speakers.

Question Type: Assumption (necessary assumption)

Asks you to identify an assumption of the author’s argument.

Question Type: Justify the conclusion (sufficient assumption)

Asks you to supply a piece of information that, when added to the premises, proves the conclusion.

Question Type: Strentgthen/support

Asks you to select the answer choice that provides support for the author’s argument or strengthens it in some way.

Question Type: Resolve the paradox

Asks you to find the answer choice that best resolves the discrepancy or contradiction.

Question Type: Weakens

Asks you to attack or undermine the author’s argument.

Question Type: Method of reasoning

Asks you to describe, in abstract terms, the way in which the author made his or her argument.

Question Type: Flaw in the reasoning

Asks you to describe, in abstract terms, the error of reasoning committed by the author.

Question Type: Parallel reasoning/parallel flaw

Asks you to identify the answer choice that contains reasoning most similar in structure to the reasoning presented in the stimulus.

Question Type: Evaluate the argument

Asks you to decide which answer choice will allow you to determine the logical validity of the argument.

Question Type: Cannot be true

Asks you to identify the answer choice that cannot be true or is most weakened based on the information in the stimulus.

What are the four main question families?

prove, help, hurt, & disprove

Which variations are a part of the PROVE family?

Must be true, main point, point at issue/point of agreement, method of reasoning, flaw in the reasoning, & parallel reasoning/parallel flaw

Which variations are a part of the HELP family?

Assumption (necessary assumption), justify the conclusion (sufficient assumption), strengthen/support, & resolve the paradox

Which variation(s) are a part of the HURT family?

Weaken

Which variation(s) are a part of the DISPROVE family?

Cannot be true

Explain flow of information for the PROVE family:

You must accept the stimulus info—even if it contains an error of reasoning—and use it to prove that one of the answer choices must be true.

Explain flow of information for the HELP family:

The information in the stimulus is suspect. There are often reasoning errors present, and depending on the question, you will help shore up the argument in some way.

Explain flow of information for the HURT family:

The information in the stimulus is suspect. There are often reasoning errors present, and you will further weaken the argument in some way.

Explain flow of information for the DISPROVE family:

You must accept the stimulus information—even if it contains an error of reasoning—and use it to prove that one of the answer choices cannot occur.

Prephrasing

Involves quickly speculating on what you expect the correct answer will be based on the information in the stimulus.

What is one mental trap you MUST avoid at all times in any LSAT section?

The tendency to dwell on past problems.

What is a signature feature of the four question families?

They define the parameters of what you can do with the information in each question.

What is accurate about correct answers for Must Be True questions?

The correct answer to a MBT question can always be proven by referring to the facts stated in the stimulus.

What are the four classifications of information that can be used to prove that an answer is correct for MBT/MSS questions?

—The actual statements of the stimulus.

—Commonsense assumptions.

—Consequences of the statements presented in the stimulus.

—Information under the “umbrella” of the statements in the stimulus.

What should you do as you analyze each answer choice for a MBT/MSS questions?

Make certain to consider whether a statement that appears “new” might actually be derived from one of the sources of information.

What should you always remember when reading stimuli?

Read closely and pay strict attention to the modifiers used by the author.

What two types of answers will ALWAYS be correct in MBT and MSS questions?

Paraphrased answers and combination answers.

Combination Answers

Answers that are the sum of two or more stimulus statements.

What are the different types of incorrect answers for MBT questions?

—Could be true or possibly true answers

—Exaggerated answers

—”New” information answers

—Shell game answers

—Opposite answers

—Reverse answers

True or False: Many = Some, but Many =/= Most, and Many =/= Some

True

How can you predict the occurrence of MBT and MSS questions?

The stimuli of MBT and MSS questions do not contain a conclusion.

Indicators for a sufficient condition are:

if, when, whenever, every, all, any, each, in order to, and people who

Indicators for a necessary condition are:

then, only, only if, must, required, unless, except, until, without, precondition

Indicators for necessary conditions subject to the “Unless Equation”

unless, except, until, and without

True or False: Either condition (necessary or sufficient) can appear first in the sentence

True

True or False: A sentence can only have one indicator

False: A sentence can have one OR two indicators

What is the format for diagramming a sufficient and necessary condition?

Sufficient Condition —> Necessary Condition

What are the valid forms of conditional reasoning?

repeat form and contrapositive

What are the invalid forms of conditional reasoning?

mistaken reversal and mistaken negation

How many main points can there be in a given argument?

There is only ever one main point to an argument

What are the two types of incorrect answers that typically appear in main point questions?

1. Answers that are true but do not encapsulate the author’s point.

2. Answers that repeat the premises of the argument rather than the conclusion.

FITB: Main point questions are Must Be True questions with an additional criterion ________

you must also identify the author’s point

From a classification standpoint, what subcategory are main point questions a part of?

Must Be True questions

What is another word for the main point?

The conclusion

What must any conditional statement consist of?

At least one sufficient condition and at least one necessary condition

Definition: Sufficient Condition

an event or circumstance whose occurrence indicates that a necessary condition must also occur

Definition: Necessary Condition

an event or circumstance whose occurrence is required in order for a sufficient condition to occur

True or False: Conditional reasoning is interchangeable with causal reasoning

False: Conditional reasoning is not the same as causal reasoning despite similarities

What is your job when it comes to conditional reasoning?

Your job is not to figure out what sounds reasonable, but rather to perfectly capture the meaning of the author’s sentence.

Defintion: Mistaken Reversal

A mistaken reversal switches the elements in the sufficient and necessary conditions creating a statement that does not have to be true.

What do you do when a stimulus that contains conditional reasoning is combined with a MBT question stem?

Immediately look for the repeat or contrapositive in the answer choices.

What are the two primary ways to increase speed in the LR section?

1. Increase general knowledge of how to attack the questions.

2. Learn to recognize the patterns that appear within the test.

Definition: LSAT Either/Or

at least one of the two, but possibly both will occur

Definition: LSAT Either/Or, But NOT Both

exactly one of the two will occur

In the case of “the only,” what is important to do?

It is important to examine what exactly “only” is modifying.

What is another word for double arrows?

Biconditionals

Definition: Double Arrows/Biconditionals

Terms in a double arrow relationship either occur together or both do not occur (double-not arrows)

What are the 3 indicators for a double arrow relationship?

1. Use of the phrase “if and only if” (or any synonymous phrases)

2. Use of the phrase “vice versa”

3. By repeating and reversing the terms