LSAT - Logical Reasoning

Necessary Assumption

A question type that seeks to bring out an unstated belief that the author must rely on for the argument to survive; if removed or negated, the argument dies.

Necessary Assumption

Aka “the requirement”

Sufficient Assumption

A question type that requires finding the missing piece of information that, if true, guarantees the conclusion is 100% true and fixes the argument immediately.

Sufficient Assumption

Aka “the guarantee”

Must-Be-True

Question type wherein the answer simply repeats or mathematically proves a fact that is already in the stimulus without bringing in new information.

Must-Be-True

aka “straight facts”

Necessary Assumptions

Question types whose answers are usually mildly worded

Necessary Assumptions

Question type whose answers contain the words: some, can, all, possible…

Sufficient Assumption

Question type whose answers are typically worded strongly

Sufficient Assumptions

Question type whose answers contain the following terms: all, any, every, never, strictly

Necessary and Sufficient Assumptions

Question types that allow for outside info.

Must-Be-True

Question type that doesn’t allow external info and requires the reader to stay strictly inside what the stimulus proves.

Argument

When a conclusion is reached by way of interaction between premises (facts) and assumptions.

Necessary Assumptions

 Goal is to find the bare min. req. for the logic to function. You are looking for something the author had to believe to make their argument. It doesn’t need to prove the conclusion by itself; it just needs to be something that, if removed, ruins the argument.

Sufficient Assumptions

Goal is to prove the conclusion 100%, without a doubt, true.

Sufficient Assumption Tool

Premise + Missing Piece → Forces the Conclusion

Necessary Assumption Tool

Conclusion exists → Therefore, this requirement MUST have been true behind the scenes

Argument

A claim that supports another claim.

Causal Claim

When the stimulus posits that X caused Y because they happened at the same time or one after the other.

Causal Claim

Question type wherein a necessary assumption establishes that no other alternative factor caused the change.

The Rogue Term / The Concept Shift

When the stimulus includes a term or concept in the conclusion that was never mentioned in the evidence or premise.

The Rogue Term / The Concept Shift

Type of argument that necessitates a necessary assumption acting as a bridge connecting two mismatched concept/terms helps resolve.

The Time Shift

When the author looks at something that happened in the past or is happening right now, and concludes the exact same thing will happen in the future.

The Time Shift

Type of stimulus that requires a necessary assumption in which the author must assume the underlying conditions will not change.

The False Dilemma

Type of necessary assumption stimulus wherein the author proves that Option A is a bad idea, and immediately concludes that we MUST go with Option B.

The False Dilemma

Type of stimulus that is resolved with a necessary assumption that states that there is no Option C. If a third, middle-ground option exists, the argument collapses.

The Survey / Sample Shift

When the stimulus involves polling a specific group of people and using their answers to make conclusions about everyone.

The Survey / Sample Shift

Type of stimulus made stronger by a necessary assumption that establishes that the said small group is truly representative of the whole group or at the very least not biased in a way that destroys the conclusion.

The Survey / Sample Shift

When the author introduces a study, survey, or sample of a very specific subgroup (the “part”) and uses their behavior or opinions to make a sweeping conclusion about everyone (the “whole”).

The Numbers vs. Percentages Trap

Type of stimulus wherein the author gives a percentage (ex/ market share went up by 10%) and concludes that the absolute of the total number went up too (ex/ they made more money overall).

The Numbers vs. Percentages Trap

When the argument is made stronger by a necessary assumption that establishes that the total “pool” didn’t shrink