Logical reasoning PrepTest 146 · Section 3 · Question 2

Incorrect. This answer provides an alternative explanation/cause of the food shortages, thus weakening the argument.

Incorrect. This answer provides counterexamples—areas where the climate was most unstable (cause) but didn't experience unrest (no effect).

Incorrect. Similar to (A), this answer provides an alternative explanation for the food shortages other than climate instability, weakening the argument.

Correct. Argument or Facts:
Argument

Valid or Flawed:
Flawed

Question Type:
Strengthen

Stimulus Summary:
Europe's climate was under flux when Rome fell. This probably caused food shortages and thus was a major cause of the fall of Rome.

Answer Anticipation:
Strengthen questions frequently feature correlation/causation flaws, so you should be on the lookout for causal language in the conclusion. Here, the conclusion clearly states that climate instability was a major cause of the fall of the Roman empire, so there's a causal conclusion.

Interestingly, however, there's a mix of causal and correlative premises. There is a correlation between the fall of the Roman Empire and a period of extreme climate changes in Europe, so there's a correlation/causation flaw here, and we can strengthen the argument using our normal methods:

(1) Eliminate an alternative cause (less likely here since the conclusion is that an unstable climate was a "major" factor, not the only factor)
(2) More examples of climate instability leading to empires falling
(3) A control Ð no cause, no effect
(4) An explanation of how the causality works

And that last point is where the causal premise comes in, as the argument itself raises a possible explanation—the climate caused food shortages, making it harder to rule the Empire. That means two things:

(1) The correct answer is unlikely to provide an explanation for the causality, as we already have one
(2) The correct answer could use any of the above strengthening methods to connect the correlation to food shortages, thus strengthening the explanation

A little more depth than the normal correlation/causation question—and a question #2 no less! But we're equipped to tackle it, so let's head to the answers.

Answer Explanation:
This answer strengthens the argument by establishing a control—a situation where the cause was absent (no climate instability, favorable agricultural conditions) and so was the effect (a thriving empire).

Key Takeaway:
While causal conclusions can be backed up with causal premises, they have to establish the causal relationship from the conclusion, usually by chaining multiple causal relationships together. If the causal premise is related to the causal conclusion but doesn't fully establish it, it's still possible that there's a correlation/causation flaw—especially if there's a correlation in the premises!

Incorrect. If anything, this answer weakens the argument by suggesting the supposed direct cause of the fall of Rome—the food shortages—were less pronounced as Rome fell.