LSAT Parallel Flaw Questions: Matching the Error, Not the Topic
Parallel flaw questions ask you to find the answer whose reasoning is wrong in the same way. Learn to name the flaw first, then match structure — not subject matter.
2026-06-01 · 7 min read
What makes parallel flaw hard
Parallel flaw questions give you a flawed argument and ask which answer contains the same flaw. The difficulty is that the right answer rarely shares the topic — it shares the broken structure. Students who match by subject matter pick traps.
The two-step method
Step 1: Name the flaw in the original argument in plain words — "it confuses a necessary condition for a sufficient one," or "it draws a causal conclusion from a correlation."
Step 2: Find the answer that commits that exact flaw, ignoring whether it is about trains, fungi, or tax policy. The match is in the reasoning, not the content.
Worked example
Original: "Everyone who succeeds works hard. Sam works hard, so Sam will succeed." Flaw: treats a necessary condition (hard work) as sufficient.
Correct parallel answer commits the same error: "Every champion trains daily. Lee trains daily, so Lee will be a champion." Same flawed structure, different topic. A trap answer might share the topic of success but reason validly.
Verbloom's structure view lets you compare the skeleton of two arguments side by side, which is exactly what these questions test.
Frequently asked questions
How is parallel flaw different from parallel reasoning?
Parallel reasoning matches the structure of a valid argument; parallel flaw matches the structure of a flawed one. In parallel flaw, both the original and the correct answer contain the same reasoning error.
Should I diagram the argument?
For conditional or quantifier flaws, a quick diagram of both the stimulus and the contender answers makes the structural match obvious.
Why are topic-matching answers usually traps?
Because the test rewards matching the logical form. An answer about the same subject can reason perfectly well, while the credited answer often sounds unrelated but breaks in the identical way.
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