PrepTest 155

(A) This is a principle for a different argument. The physician didn't conclude that physicians "should advocate moderate consumption" of red wine. The conclusion was that the evidence of red wine's health benefits is misleading.

(B) This would actually weaken the physician's argument, as the red wine advocates do have persuasive statistical evidence on their side. So, according to (B), the red wine advocates' argument is pretty good, not inconclusive!

(C) This is a principle for a different argument. The physician didn't conclude that physicians shouldn't recommend moderate red wine consumption, much less that physicians "should not make any recommendations regarding the consumption of food or drink." The conclusion was that the evidence of red wine's health benefits is misleading.

Argument or Facts:
Argument

Valid or Flawed:
Flawed

Question Type:
Strengthen with a Necessary Premise (Principle)

Stimulus Summary:
Health experts who advocate moderate alcohol consumption for health benefits say red wine is the healthiest booze. And yeah, statistics say people who drink red wine in moderation are less likely to die of heart disease than other moderate drinkers. But the red wine proponents can't explain which mechanism is responsible for this difference, so the evidence for their claims is inconclusive.

Strategy Overview:

1. Argument or facts? Always argument, so identify premises and conclusions of argument
2. Anticipate why the premises are not enough to show that the conclusion is true
3. Use anticipations to select the answer choice that:
   1. Strengthens the conclusion of the argument, and
   2. Is necessary for the conclusion of the argument
      1. Can use "negation test" to double-check: if this answer choice isn't true, does the conclusion become untrue as well? If so, it's necessary for the conclusion of the argument, and it is the correct answer

Answer Anticipation:
This is technically a Strengthened with a Necessary Premise question, but we could approach it with the same strategy as a Principle (Strengthen) question. And that's not surprising since the strategies for those two questions are so similar. In both, we'll identify the gap between the premsies and conclusion, and then look for an answer choice that connects the premise to the conclusion.

And what is the gap between the premises and conclusion in this argument? Basically, this argument boils down to "correlation isn't causation." There's correlative evidence for the claim that red wine has more health benefits than other alcoholic drinks. However, we can't explain how red wine protects drinkers against heart disease. And for that reason, the evidence in favor of red wine's healthfulness is "inconclusive," according to the physician.

Since we're looking for a principle here, we'll look for a rule that says something like, "evidence that doesn't explain the causal mechanism behind a health benefit is inconclusive."

Answer Choice Explanation:
Here's that "conclusive" concept we've been looking for. And this matches our anticipation perfectly: conclusive evidence that a food or drink has a specific health benefit requires an explanation of the mechanisms involved. If this rule is applied to the red wine argument, then the physician's conclusion is correct — red wine advocates don't have conclusive evidence for their claims. So this connects the premise to the conclusion, and it passes the negation test, too — if you don't need to explain the mechanism to have conclusive evidence, then the physicians' conclusion is invalid.

Key Takeaway:
Principles are rules — the LSAT version of laws. Therefore, when you're looking for a necessary principle, it needs to be directly related to the conclusion of the argument in the stimulus. Just like you couldn't judge whether or not someone deserved a speeding ticket based only on a set of laws for the inheritance of physical property, you can't judge an argument's conclusion based on a principle that doesn't apply directly to the argument.

(E) We're looking for a rule about how to tell whether or not evidence of a health benefit is conclusive, not about whether or not you should even look for a casual mechanism behind a health benefit. This rule doesn't fit, and it is incorrect.