LR Bible 2015, page 474, ex. 3

[DlarehAtsok]

"Activist: Food producers . . ." In the answer key, it is said that this is an error in the use of evidence, where some evidence against a position is taken to prove that position is false. Could you explain me why? I prephrased it as "lack of evidence for a position is taken to prove that position is false", because the stimulus claimed first that an experiment supported the safety of this process, and then this experiment was rejected by a group of scientists. So, in the end there was no proof that the irradiation was safe and the argument (wrongly) claimed that is unsafe. I also believe that answer choice (A) is closer to this, but probably I am wrong

[Jonathan Evans]

Dlareh,

These flaw questions can sometimes present difficulty even when you understand the error in the reasoning. They require an extra step, an abstraction of the elements of the argument into a form that you can match with the answer choices.

You can prephrase the flaw as follows:

Author concludes that practice is unsafe because evidence of safety is discredited (classic "absence of evidence is not evidence of absence").

Get one level more abstract:

Author concludes lack of evidence for claim (safety) is proof that claim is false (food unsafe).

Then match this abstract prediction part by part with the answer choices:

A) failure to prove a claim === match with lack of evidence for claim; proof of denial of claim === match with proof that claim is false. MATCH
B) methodological flaws in past studies === match with lack of evidence for claim; not possible to devise alternatives NO MATCH
C) basically, so what? not germane to the connection the Activist is trying to make. no match.
D) also, so what? not relevant.
E) ad hominem. not necessary to reach conclusion. no match.

The book does an excellent job explaining these answer choices in detail. Essentially, to get these right, you've got to practice getting this prephrasing down to a...science.