Causation Flaws on the LSAT: Correlation Is Not Enough

Correlation-causation is one of the most frequently tested flaws in LSAT Logical Reasoning. You will almost certainly see it multiple times on any given test.

The basic structure is always the same: the argument observes that two things are associated, then concludes that one must have caused the other. That leap is the flaw.

Understanding this flaw deeply — not just being able to name it — is what allows you to handle flaw questions, weaken questions, and assumption questions that involve causal reasoning.

A causal argument shows that X and Y tend to occur together (or that Y increased after X increased), then concludes that X caused Y.

The flaw is that a correlation between two things does not establish that one caused the other. The two things may be related for entirely different reasons.

Example: "In cities with more coffee shops, residents report higher life satisfaction. Therefore, access to coffee shops increases life satisfaction."

The observation is real — more coffee shops correlate with higher reported satisfaction. But the conclusion that coffee shops cause the satisfaction goes beyond what the evidence shows.

The argument has not ruled out alternative explanations. That gap is the flaw.

When you see a correlation-causation flaw, there are three types of alternative explanations the argument ignores:

1. Reverse causation: The direction of causation may be backwards. Rather than X causing Y, Y may cause X. In the coffee shop example: higher life satisfaction may cause residents to open or visit more coffee shops, not the other way around.

2. A third factor (common cause): A third variable Z may cause both X and Y independently. For instance, wealthier cities may both have more coffee shops AND have residents who report higher life satisfaction — the wealth is the true cause of both.

3. Coincidence: X and Y may simply happen to occur together without any causal connection at all. A change that coincides with another change is not necessarily connected to it.

The LSAT answer choices for flaw, weaken, and assumption questions in causal arguments typically exploit one or more of these three alternative explanations.

Causal flaws appear in a standard pattern. Here is what to look for:

The stimulus presents data showing that two things are associated. The conclusion is that one thing caused the other (or that one thing will cause the other in the future, or that the cause should be applied to produce the effect).

Common phrasings in the evidence: "occurs more frequently among," "is associated with," "has been observed alongside," "increased after," "correlates with."

Common phrasings in the conclusion: "causes," "leads to," "produces," "results in," "is responsible for," "accounts for," "is the reason for."

When you see a correlation in the evidence and a causal claim in the conclusion, flag it immediately. The argument has almost certainly committed this flaw.

On a flaw question, the correct answer will describe the causal error in abstract terms. Common phrasings include:

"Takes a correlation as evidence of causation."

"Concludes that one thing caused another on the basis of their being associated."

"Fails to consider that the relationship could be the reverse of what is claimed."

"Overlooks the possibility that a third factor caused both X and Y."

Notice that these are general descriptions of the error — they do not repeat the specific content of the stimulus. That is typical of LSAT flaw answers. They describe the logical move, not the subject matter.

Wrong flaw answers often describe real errors but ones the argument did not commit, or they describe the argument's content without identifying the logical mistake.

When a causal flaw argument shows up in a weaken question, the correct answer will introduce or support one of the three alternative explanations.

"Reverse causation" weakener: "Studies show that people with higher life satisfaction are more likely to open small businesses, including coffee shops."

"Third factor" weakener: "Cities with higher average incomes tend to have both more coffee shops and higher reported life satisfaction scores."

"Coincidence" weakener: "Researchers who controlled for economic and demographic factors found no significant relationship between coffee shop density and life satisfaction."

Any answer that provides an alternative explanation for the correlation weakens the causal conclusion. The argument assumed causation; the weakener gives a reason to doubt it.

When a causal argument shows up in a necessary assumption question, the correct answer is typically: the argument assumes that one of the three alternative explanations does not apply.

For the coffee shop example, a necessary assumption would be: "The higher life satisfaction in cities with more coffee shops is not primarily explained by those cities having higher average incomes."

Negate it: "The higher life satisfaction in those cities IS primarily explained by higher average incomes." If that is true, the causal conclusion about coffee shops collapses. So the assumption is necessary.

This is the connection between causal flaws and assumption questions: when an argument assumes causation from correlation, it also necessarily assumes that the alternative explanations do not account for the data.

Selecting the answer that just restates the evidence. Wrong answers sometimes describe what the argument observed rather than the logical error it made. "The argument points out that cities with more coffee shops have higher satisfaction" is not a flaw — it is just a description of the premise.

Missing reverse causation. Students often spot the third-factor alternative but miss reverse causation. Always check both directions of the relationship.

Confusing correlation with causation in the answer choices. Some wrong answers themselves commit logical errors. Read each answer carefully for what logical claim it is making, not just whether it sounds related to the stimulus.

Applying this flaw when the argument does not use causal language. Not every association-based argument commits the causation flaw. If the conclusion is also only a correlation (not a cause), the flaw does not apply.

Q: How do I know if the argument is claiming causation vs. just correlation? Look at the language in the conclusion. If the conclusion uses words like "causes," "produces," "leads to," "results in," "is responsible for," or "accounts for," the argument is claiming causation.

Q: Can an argument establish causation legitimately? Yes — by ruling out alternatives. An argument that shows the correlation holds even after controlling for third factors, and that the direction of causation makes sense, is stronger. The LSAT will not ask you to question a properly supported causal claim.

Q: Is this flaw the same as the post hoc ergo propter hoc fallacy? That Latin phrase means "after this, therefore because of this" — concluding causation from sequence rather than just association. It is a subtype of the same family of errors the LSAT tests as correlation-causation.

Q: Does this flaw appear in reading comprehension too? Yes. RC passages sometimes present arguments with causal claims. The same principles apply when an RC question asks you to evaluate reasoning in the passage.

Causation flaws appear in flaw questions, weaken questions, strengthen questions, and necessary assumption questions. Recognizing the pattern quickly — and knowing which of the three alternatives to look for — is a repeatable skill.

Verbloom's flaw recognition drills cover correlation-causation and nine other major flaw types, with plain-English explanations after each question.

Practice at verbloom.dev.