LSAT Logic and Question Types

These flashcards provide a breakdown of LSAT logical concepts including premise/conclusion identification, conditional logic, question type recognition, and the various logical flaws tested on the exam.

Argument

A combination of premises and a conclusion that is trying to convince you of something.

Premise

The evidence from which a conclusion is drawn; everything other than the conclusion that is always assumed to be true.

Conclusion

The point the argument is trying to convince you of; it is not necessarily true and should always be underlined.

Sufficient

A dependent variable representing the thing that needs something; it should always have "$\text{if}$ " written in front.

Necessary

An independent variable representing the thing that is needed; it can exist by itself.

Contrapositive

A logical principle stating that if you take away the necessary, you can no longer have what it was necessary for.

Mistaken Reversal

The incorrect assumption that if you have the necessary, you must also have the sufficient.

Mistaken Negation (Incorrect Assumption)

The incorrect assumption that because you do not have the sufficient, you do not have the necessary; taking the nonexistence of something as evidence that a necessary precondition did not exist.

Main Point (Correct Answer characteristics)

A paraphrase of the final conclusion; identifies the primary claim without introducing new information or exaggeration.

Must be True (Correct Answer characteristics)

Information that can be properly inferred or is most strongly supported by the passage, often appearing as a paraphrase or a combination of statements.

Cannot be True (Correct Answer characteristics)

A claim that is $100\%$ disproven by the statements in the stimulus; used as evidence against a hypothesis or to undermine an assertion.

Method of Reasoning

An abstract description of the argumentative strategy or technique employed in the argument.

Flaw (the question type)

The evil sister of Method of Reasoning that provides an abstract description of why the reasoning in the argument is fallacious or vulnerable to criticism.

Weakening (Correct Answer characteristics)

Information that, if true, undermines the exact conclusion between $1\%$ and $100\%$.

Strengthening (Correct Answer characteristics)

Information that, if true, justifies or supports the exact conclusion between $1\%$ and $100\%$.

Assumption (Correct Answer characteristics)

Something that is $100\%$ necessary for the conclusion to follow; if the answer choice is not true, the conclusion fails.

Justify Question (Sufficient Assumption)

An answer choice that proves the conclusion $100\%$; if the answer is true, the conclusion must be true.

Principal

A broad rule or judgment used in the stimulus to deduce a specific case, or provided in the answer choices to justify an argument's reasoning.

Resolve the Paradox (Correct Answer characteristics)

Information that increases the likelihood that two conflicting ideas in the stimulus can coexist.

Parallel Reasoning (Correct Answer characteristics)

An argument that exhibits the same structure and logical features as the stimulus, regardless of subject matter or order.

Evaluate the Argument (Correct Answer characteristics)

A question whose opposite responses would result in one strengthening and the other weakening the argument.

Point at Issue

The specific statement about which two speakers directly agree and disagree; one speaker would say "yes" and the other would say "no" to the correct answer choice.

Mistaken Cause and Effect

The error of assuming causality based on event sequence (temporal relationship) or correlation without excluding alternative explanations or event reversals.

Appeal to Authority

An error where a claim is accepted based on the judgment of experts in a field that is irrelevant to the matter at hand.

Straw Man

The distortion of an opponent's position to make it more extreme and easier to refute.

Lack of Relevant Evidence for the Conclusion

Citing irrelevant data or drawing a conclusion that is broader in scope than the advances in evidence warrant.

Survey Error

Generalizing from a small, biased, or unrepresentative sample, or using improperly constructed survey questions.

Errors in Use of Evidence

Treating the failure to disprove a claim as proof that the claim is true, or treating evidence that a conclusion could be true as proof that it is in fact true.

Uncertain Use of a Concept

An ambiguous use of a key term where the meaning shifts from one use to the next or the term remains undefined.

Error of Division

Presuming that what is true of a whole must also be true of its constituent parts.

Numbers and Percentage Errors

The improper equation of a percentage of a total to a definite quantity, or vice versa.

False Analogy

Treating two cases as similar when they actually differ in a critical or important respect.

Error of Composition

The assumption that a characteristic true of parts of a group is true of the whole group or each of its members.

Appeal to Numbers/Popular Opinion

Discrediting or supporting a claim based solely on the fact that a majority of people believe it to be true or false.

Time Shift Errors

The uncritical assumption that conditions remain consistent over time, such that what was true in the past must be true in the future.

False Dilemma

The assumption that only two courses of action or possibilities are available when others may exist.

Source Argument

Attacking the character or motives of a person making a claim rather than addressing the claim or argument itself.

Internal (Self) Contradiction

Basing a conclusion on claims that are inconsistent with each other or making incompatible assumptions.

Appeal to Emotion

Using emotive language rather than reason in an attempt to persuade the audience.

Exceptional Case/Overgeneralization

Basing a general or universal claim on a single example, an exceptional case, or a sample size that is too small.

Circular Reasoning

An argument that presupposes the truth of what it sets out to prove; the premise is essentially a restatement of the conclusion.

Sufficient Condition Indicators

In order to, Whenever, Any, Every, All, When, People Who, If

Necessary Condition Indicators

Required, Must, Unless, Without, Only if, Only, Except, Until

Premise Indicators

Because, For example, For, Since, Given that, Due to, Moreover, Furthermore, For this reason

Conclusion Indicators

Thus, Therefore, In conclusion, Hence, Follows that, Shows, Consequently, As a result, So, Accordingly, Clearly