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Parallel
Reasoning

Master the art of identifying arguments that share the same logical structure, one of the most challenging LSAT question types.

LSAT Logical Reasoning

What Is Parallel Reasoning?

Parallel reasoning questions ask you to find an answer choice whose argument has the same logical structure as the stimulus argument. The specific topic does not matter: what matters is the pattern of reasoning.

Why Parallel Reasoning Matters

High Frequency
Appears 1 to 3 times per scored LSAT section, often among the hardest questions.
Time Intensive
Long answer choices make this question type a major time investment: strategy is essential.
Transferable Skill
The ability to abstract logical structure strengthens performance on every LR question type.

Building Blocks of Argument Structure

To match structures, you need to identify four elements in every argument:

1
Conclusion type: Is it absolute, conditional, a recommendation, or a prediction?
2
Premise types: Are the premises facts, generalizations, conditionals, or opinions?
3
Logical connectors: Words like "all," "some," "no," "if...then," "unless" shape the structure.
4
Reasoning pattern: How do the premises connect to the conclusion (e.g., analogy, cause-effect, rule application)?

The Core Rule: Match the Blueprint

STIMULUS Premise 1 (conditional) Premise 2 (fact) therefore Conclusion (absolute) ABSTRACT FORM
\(A \rightarrow B, A \therefore B\)
 MATCH CORRECT ANSWER Premise 1 (conditional) Premise 2 (fact) therefore Conclusion (absolute) ABSTRACT FORM
\(X \rightarrow Y, X \therefore Y\)
 =

Five Common Reasoning Patterns

1
Modus Ponens: \(A \rightarrow B, A \therefore B\)
2
Modus Tollens: \(A \rightarrow B, \neg B \therefore \neg A\)
3
Disjunctive Syllogism: \(A \lor B, \neg A \therefore B\)
4
Generalization to Particular: \(\text{All } X \text{ are } Y. Z \text{ is an } X. \therefore Z \text{ is } Y.\)
5
Analogy: A is like B in relevant ways. B has property P. Therefore A probably has P.

Parallel Reasoning vs. Parallel Flaw

Parallel Reasoning Parallel Flaw
Stimulus Valid or well-structured argument Contains a logical error
Your task Match the correct pattern Match the same error
Conclusion Properly supported Not properly supported
Strategy overlap Both require abstracting the argument's structure

Step-by-Step Strategy

1
Identify the conclusion. Find the main claim the stimulus is trying to prove.
2
Classify the conclusion type. Is it absolute, conditional, comparative, a recommendation, or a prediction?
3
Map the premises. Note the number, type, and logical role of each premise.
4
Abstract the pattern. Replace content with variables: "\(A \rightarrow B, A \therefore B\)"
5
Eliminate by conclusion first. Quickly cross out any answer whose conclusion type doesn't match.
6
Compare remaining answers by premise structure. The match must be complete.

Worked Example: Simple Pattern

\(\text{All } A \text{ are } B\)
\(X \text{ is an } A\)
\(\therefore X \text{ is } B\)
 =
\(\text{All } C \text{ are } D\)
\(Y \text{ is a } C\)
\(\therefore Y \text{ is } D\)

Worked Example: Conditional Chain

Budget Approved if...then Project Launches if...then New Staff Hired A (given) B C (conclusion)
Pattern: \(A \rightarrow B, B \rightarrow C, A \therefore C\)

Worked Example: Tricky Distractor

Pattern: \(\text{Some } A \text{ are } B. \text{ All } B \text{ are } C. \therefore \text{ some } A \text{ are } C.\)

✓ Correct Match
"Some teachers are musicians. All musicians read music. Therefore some teachers read music."
✕ Tempting Wrong
"All chefs are artists. Some artists paint. Therefore some chefs paint." (Switches "some" and "all" in the premises.)

Elimination Power Moves

You can often eliminate 2 to 3 answer choices in seconds by checking these quick filters before reading the full argument:

1
Conclusion type mismatch: If the stimulus concludes with "therefore some..." and an answer concludes with "therefore all..." it's out.
2
Polarity mismatch: If the stimulus has an affirmative conclusion, eliminate answers with negative conclusions (and vice versa).
3
Premise count mismatch: If the stimulus has two premises, answers with three or one premise are unlikely matches.

Abstracting with Variables

The most reliable technique is to replace each concept with a letter. Here is a side-by-side translation:

Original Language Variable Form
"All cats are mammals" \(\text{All } A \text{ are } B\)
"If it rains, the game is canceled" \(P \rightarrow Q\)
"Either we leave now or we miss the train" \(R \lor S\)
"No reptiles are warm-blooded" \(\text{No } C \text{ are } D\)
"Some students passed the exam" \(\text{Some } E \text{ are } F\)

Common Mistakes

✕ Topic Matching
Choosing an answer because it discusses a similar subject (e.g., both about sports). Topic is irrelevant: structure is everything.
✕ Ignoring Quantifiers
Treating "some," "all," "most," and "no" as interchangeable. Each quantifier produces a different logical form.
✕ Reversed Conditionals
Confusing "\(A \rightarrow B\)" with "\(B \rightarrow A\)". The direction of the conditional is part of the structure.

Quick-Reference Summary

Element Must Match? Example Check
Conclusion type Yes "Some..." = "Some..."
Conclusion polarity Yes Affirmative = Affirmative
Number of premises Yes Two premises = Two premises
Premise types Yes Conditional + Fact = Conditional + Fact
Reasoning pattern Yes Modus Ponens = Modus Ponens
Subject matter / topic No Cats vs. Cars: doesn't matter
Length of argument No Word count is irrelevant

Question 1 of 5

Which of the following arguments is most similar in its reasoning to the argument above?

Question 2 of 5

Which of the following most closely parallels the reasoning above?

Question 3 of 5

Which of the following arguments most closely parallels this reasoning?

Question 4 of 5

Which of the following most closely parallels the reasoning in the stimulus?

Question 5 of 5

Which of the following is most similar in its pattern of reasoning to the argument above?