PrepTest 154, Section 4, Question 7
Late blight is a disease affecting tomato plants(40 more words not shown)
The flawed nature of the(16 more words not shown)
- Asince radiation therapy(28 more words not shown)
- Bsince scurvy is(18 more words not shown)
- Csince malnutrition can(16 more words not shown)
- Dsince paracetamol is(18 more words not shown)
- Esince calcium deficiency(29 more words not shown)
Reading the argument
A treatment doesn't tell us what caused the disease.
Copper helps treat late blight. Fine. But why conclude that the plant developed late blight because it lacked copper? The copper could help address a problem that began for some entirely different reason. Effective treatment and original cause are two different questions.
Try the same reasoning with chemotherapy: because chemotherapy can treat cancer, must cancer be caused by a shortage of those treatment chemicals? The effectiveness of a treatment alone wouldn't establish that account of the cause. We would need separate evidence that the shortage produced the disease.
What we’re looking for
The question asks for parallel reasoning that exposes the mistake. We've already made an example. Look for a problem, something that treats it, and then the unsupported conclusion that a lack of the treatment caused the problem. Keep that direction straight. Starting with a known cause and proposing a remedy would be a different argument.
Working the answers
- A
This starts promisingly: radiation therapy treats some cancers, much like copper treats late blight. But the conclusion goes somewhere else. It says more radiation will work better. Our argument doesn't claim that more copper is a better treatment; it claims that too little copper caused the disease. To match, A would need to infer that the cancer arose from a lack of radiation.
- B
This starts by identifying the cause: a vitamin C deficiency causes scurvy. It then concludes that giving vitamin C can treat the condition. The original starts with an effective treatment and guesses the cause from it. The order and job of those facts matter, even though both arguments mention a deficiency.
- C
This also starts with a cause of health problems: malnutrition. Its mistake is then to assume that more and more food must make someone healthier. That's a claim that more food always improves health, not a conclusion that the lack of a known treatment caused the illness. C doesn't reproduce the inference we challenged.
- DCorrect
Headaches take the place of late blight, and paracetamol takes the place of copper. In each case we know the substance helps treat the problem. Then the argument concludes that a lack of that substance caused the problem.
Nothing about successful treatment alone establishes the claimed shortage. This matches both the starting evidence and the unsupported causal conclusion, which is what a parallel needs to do.
- E
This begins with a stated cause: calcium deficiency can produce brown spots. It then assumes that avoiding that cause guarantees no spots. Other causes of spots could still exist. That is a different mistake from discovering that calcium treats spots and inferring that a calcium shortage must have caused them. Don't let the shared topic of plants and minerals substitute for matching the reasoning.
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