Reasoning Flaw
LSAT glossary · Logical Reasoning
Definition
A gap in the relationship between an argument's premises and its conclusion such that, even if every premise is granted as true, the conclusion does not necessarily follow. Reasoning flaws never reside in the premises themselves or in the conclusion itself — only in the support relationship between them. On the LSAT, the test-taker accepts the premises as given and asks whether they actually justify the conclusion, framing the gap as "the author fails to consider..." or "the author takes for granted that..."
Reasoning Flaw in plain English
A reasoning flaw is a gap between the evidence and the conclusion — the reasons given just don't actually prove the point, even if you accept every reason as 100% true. The key trick on the LSAT is that you never argue with the facts they hand you; you only ask, "Okay, granting all that, does it REALLY lead to this conclusion?" It's like a detective saying "the suspect owns a red car, and the getaway car was red, therefore he did it" — the fact is true, but it doesn't get you to the conclusion, because lots of people own red cars. The flaw always lives in that jump from evidence to claim, never in the evidence itself.
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