LSAT (Law School Admission Test)Logical ReasoningEasy
City Official: Our new public transportation system, which includes expanded bus routes and a new light rail line, has been a resounding success. Since its implementation, traffic congestion during peak hours has decreased by 20%, and ridership has increased by 30%. This clearly demonstrates the effectiveness of our investment. Which of the following points to a flaw in the city official's reasoning?
- AIt does not provide a comparison to other cities' public transportation systems.
- BIt assumes that the new system is the sole cause of the decrease in traffic congestion.
- CIt overlooks the possibility that some residents still prefer to drive their personal vehicles.
- DIt fails to consider the environmental impact of increased public transportation.
Show answer & explanationAnswer & explanation
Correct answer: B. It assumes that the new system is the sole cause of the decrease in traffic congestion.
The official attributes the decrease in traffic congestion and increase in ridership solely to the new public transportation system. This is a causal flaw: assuming that because two things happened concurrently, one *must* have caused the other, without considering other potential factors that could have contributed to the observed changes.
Why the other options are wrong
- A. Comparing to other cities might provide context, but the absence of such a comparison isn't a flaw in the internal logic of *this* argument about *this* city's system.
- C. The argument acknowledges increased ridership but doesn't need to claim that *no one* prefers driving. The focus is on the *overall* decrease in congestion, not individual preferences.
- D. While environmental impact is a relevant consideration, the argument is about the system's effectiveness in reducing congestion and increasing ridership, not its environmental effects. This is outside the scope of the stated reasoning.
Causal Fallacy (Assumed Sole Cause)
A flaw where an argument attributes an effect to a single cause, ignoring other potential contributing factors or alternative explanations for the observed outcome.
- Assumes one cause is the only cause
- Ignores confounding variables
- Weakens a causal conclusion
Memory trick: Don't assume one thing is the ONLY thing!