Self-study
Wirth: Support All efforts to identify a gene responsible for predisposing people to manic-depression have failed. ██ █████ ██████ ███ ███████████ ███ █████ ████ █████ ██ ██ █████████████████ ██████ ██████████ ██ █████ ███████████ ███ ██████ ███ █████ ████ ████ ██████ ███ ███████████ ███████████ ██ ████████████████ ██ ██████ ██████
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Summarize Argument
Wirth concludes that no one is genetically predisposed to manic-depression. He supports this by saying that all attempts to identify a “manic-depression gene” have failed, and most researchers now agree that no such gene exists.
Identify and Describe Flaw
Chang points out that Wirth’s argument is flawed because his evidence doesn’t support his conclusion. Just because there’s no “manic-depression gene” doesn’t mean that people can’t be genetically predisposed to manic-depression. Wirth assumes there’s only one possible cause of genetic predisposition, but other factors, like multiple genes interacting, could also be involved.
22.
Which one of the following ████ ██████████ █████████ ███████ █████████ ██ ███████ █████████
a
It presupposes only ███ ███████████ █████ ████ ████ ███ ███████
Wirth presupposes that there’s only one possible cause of genetic predisposition— a “manic-depression gene.” But Chang points out that other factors, like multiple genes interacting, could cause someone to be genetically predisposed to manic-depression instead.
b
It depends on ████████ ██████ ██ ████████ ████ ██████████ ████ ██████
Wirth’s pieces of evidence— efforts that have failed to find a “manic-depression gene” and researchers who agree that no such gene exists— do not contradict each other. Also, Chang doesn’t criticize Wirth on this front; instead, he explicitly accepts Wirth’s evidence.
c
It relies on ███ ███████ ██ ███████ ██ ██ ████ ███████ ███ ████████ █████ ██ ██████████
Presumably the researchers that Wirth cites aren’t experts in some field other than genetics. But even if they were, Chang doesn’t criticize Wirth’s evidence at all; he accepts it.
d
It disallows in █████████ ███ ████████ ████ █████ ██████████ ███ ███████████
Chang presents evidence that disconfirms Wirth’s conclusion, but Wirth never claims to disallow such evidence on principle. And even if he did, that doesn’t describe Chang’s criticism of Wirth’s argument.
e
It treats something ████ ██ ██████ ████████ ██ ██████ ██ ████ ███████████
Wirth does treat the existence of a “manic-depression gene” as impossible, but so does Chang and so do the researchers. In other words, it’s not “merely unlikely” that a “manic-depression gene” exists, it actually is impossible. Also, Chang doesn’t criticize him on this front.