Logical reasoning PrepTest 124 · Section 1 · Question 22

Incorrect. If the Doctor hadn't presented information supporting the shift away from the long-believed medical opinions, then this answer might be correct. However, she doesn't ignore those opinions—she rebuts them with new information.

Incorrect. Unless there's a reason to believe that there's a shift in meaning, there's no need to clearly define a word that has a common meaning.

Incorrect. Being overweight is relative to the person, so the argument does take this into account.

Incorrect. The argument doesn't establish anything as being sufficient to make one unhealthy. It establishes that those who are considerably underweight are less healthy than those who are overweight, but that's neither sufficient nor unhealthy.

Correct. Argument or Facts:
Argument

Valid or Flawed:
Flawed

Question Type:
Errors in Reasoning

Stimulus Summary:
Being overweight has been linked to health issues, but those who are slightly overweight are healthier than those very underweight, so being overweight is sufficient to be healthy.

Answer Anticipation:
We've talked extensively about some of the common types of logic that show up repeatedly on the LSAT. Three of the most common types of logic are conditional logic, causal relationships, and comparisons. This argument hints at all three!

The conclusion here establishes being slightly overweight as a sufficient condition for being healthy. A conditional conclusion would normally be flawed in that the premises establish the negation or reversal of the statement. Here, however, there aren't conditional premises, so we don't have a conditional logic flaw.

The causal relationship here is actually absent—the premises discuss a correlation, and the conclusion, in putting forward a conditional relationship, doesn't talk causality, either. Therefore, there's no correlation/causation flaw.

Finally, we have relative/comparative language in the premise—"healthier." When the premises are relative, there's a chance that the argument will be flawed in that it jumps to absolute language. Which it does here! The conclusion is about being "healthy." You can be healthier than someone else while still being relatively unhealthy—being in a coma is worse than having a mild cold, but neither person is healthy. The argument jumps from relative to absolute language, and the correct answer should reflect that.

Answer Explanation:
This answer highlights the shift from a relative property—"healthier"—to an absolute one—"healthy."

Key Takeaway:
Look out for relative language—"most/least"; anything ending in "-ier" or "-est." The LSAT will frequently jump between that relative language and absolute language, which is flawed. After all, one basketball player may be shorter than another, but that doesn't mean the shorter player is short.