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Difficulty: MediumWeakening Arguments

Historians long believed that the sudden economic decline of the coastal city of Thalassa in the fourth century BCE was caused by a major earthquake that destroyed its main harbor. However, recent geological surveys confirm that the harbor suffered no structural damage from seismic activity during that era. Researchers therefore conclude that a severe, prolonged drought must have been the primary cause of Thalassa's economic collapse.

Which of the following, if true, most seriously weakens the researchers' argument?

  1. A
    Pollen samples from sediment layers around Thalassa dating to the fourth century BCE indicate a dramatic drop in agricultural crop yields consistent with arid conditions.
  2. B
    Excavations of domestic dwellings in Thalassa revealed that fourth-century BCE residents increasingly stored water in ceramic jars rather than subterranean cisterns.
  3. Historical records reveal that a newly constructed overland trade highway bypassed Thalassa during the fourth century BCE, causing the majority of regional merchant traffic to reroute.Answer
  4. D
    Seismic events in neighboring inland cities during the fourth century BCE frequently caused severe disruptions to local agricultural production.
  5. E
    Artifacts recovered from Thalassa's market square show a decline in the variety of imported luxury goods beginning in the fifth century BCE.

Answer

The argument is most seriously weakened by the statement that a newly constructed overland trade highway bypassed Thalassa during the fourth century BCE, rerouting merchant traffic.
The argument relies on ruling out seismic harbor damage to conclude that drought was the primary cause of Thalassa's economic downfall. The correct answer introduces a plausible alternative cause—a major shift in regional merchant traffic due to a new overland trade highway—which explains the economic collapse independently of drought. This severely undermines the necessity of the drought conclusion.

Step-by-Step Solution

1
Identify the premise and conclusion of the argument.
Premise: Harbor facilities suffered no seismic damage. Conclusion: A prolonged drought must have been the primary cause of Thalassa's economic collapse.
Understanding the logical jump from ruling out harbor earthquake damage to assuming drought causality isolates the argument's core vulnerability.
2
Identify the logical flaw.
The author assumes a false dichotomy—that if earthquake damage to the harbor did not cause the decline, drought must be the sole remaining primary cause.
To weaken an argument based on an exclusive cause assumption, one should introduce an alternative explanation for the observed outcome.
3
Evaluate the options for a viable alternative cause.
The rerouting of regional merchant traffic via a new overland highway explains the economic decline without relying on drought.
Providing an alternative cause directly undermines the claim that drought was necessarily the primary driver.

Key Concept

Weakening an argument by presenting an alternative cause for the observed outcome
Estimated Time:1m 30s
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Topics

Weakening Arguments

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