Logical reasoning PrepTest 121 · Section 1 · Question 20

Incorrect. The argument limits itself to discussing "some" cases of high blood pressure, so this answer about "all" cases is too strong.

Incorrect. The conclusion doesn't care if lowering stress can lower blood pressure since that's not what the principle is about. The principle only cares if lowering stress is the only way to treat an illness. As such, the argument doesn't assume that lowering stress does or does not lower blood pressure; it establishes that it's not the only thing that does so.

Incorrect. This answer connects stress and medication, but not in the way that the argument relies on. Even if reduced stress does reduce a person's responsiveness to medication, that could still allow the medication to work to cure high blood pressure.

Incorrect. The argument doesn't assume that medicine is the only thing that can treat these cases of high blood pressure, as that's not relevant to the principle. What matters is whether something other than lowering stress can treat a disease—whether or not that thing is itself the only potential treatment.

Correct. Argument or Facts:
Argument

Valid or Flawed:
Flawed

Question Type:
Strengthen with Necessary Premise

Stimulus Summary:
Medicine can treat some high blood pressure cases
Illness caused by stress → Cured only by reduction in stress
Therefore - Some cases of high blood pressure not Caused by stress

Answer Anticipation:
As with many Strengthen with Necessary Premise questions, there's conditional logic here. While it's a bit tricky to diagram, that second premise ("Since . . . ") is a conditional principle. And when a Strengthen with Necessary Premise question has a single conditional principle, it usually attempts to apply it to a specific case, and it is usually flawed in that it fails to establish that the sufficient condition of the principle is met.

Here, the argument concludes that a certain illness isn't caused by stress, so we'll need to take the contrapositive of the principle:
not Cured only by reduction in stress → not Illness caused by stress

So to reach the conclusion that these cases of high blood pressure aren't caused by stress, it would need to be established that they were cured by something other than a reduction in stress.

Doesn't the argument do that in stating that medication was able to cure it? Only if that medication doesn't work by lowering stress. If the medicine reduces stress, then the sufficient condition of the principle isn't met and it doesn't apply to the given situation, causing the argument to fall apart.

Answer Explanation:
This answer connects medicine and stress in a way that guarantees the sufficient condition of the principle (well, its contrapositive) is met and thus it applies to the given situation. If medicine used to treat high blood pressure doesn't reduce stress, then the cases of high blood pressure that are treatable with medication can be treated with something other than the reduction of stress and thus aren't caused by stress. If the medication does work by reducing stress, then the argument falls apart. This answer is therefore correct.

Key Takeaway:
When a Strengthen with Necessary Premise (or Sufficient Premise) question establishes a conditional principle and attempts to apply it to a specific situation, it's usually flawed in that it fails to establish that the sufficient condition is met. Your first check should be to see if that's the case!