Self-study
Of the many works in a collection from Japan's Tokugawa period that the museum will soon put on display, Support those that are most sensitive to light, as well as the most valuable pieces, will be on display for two weeks only. █████ ████████ ███████ ███ ██████ ███████ ████ ██ ██ ███████ ███ ███ █████ █████ ██ ██ ██ ███████ █████ ███ ████ ████████ ██████ ██ ███ ███████████
Method of Reasoning
The author identifies two types of paintings that will be on display for only two weeks: those that are sensitive to light and those that are most valuable. The author then concludes that Hoitsu’s painting, which will be on display for only two weeks, must be a specific one of those two types (among the most valuable).
Identify and Describe Flaw
This is an example of an argument mistaking a sufficient condition for a necessary one. A painting being among the most valuable pieces is sufficient for it to be displayed for only two weeks, but it’s not necessary. Just because Hoitsu's painting is displayed for only two weeks, we can't conclude that it's among the most valuable pieces.
In fact, the argument gives another example of paintings that are also displayed for just two weeks: paintings that are sensitive to light. So the argument isn't just committing sufficient-necessary confusion, it's also arbitrarily assuming one of two possible explanations for why Hoitsu's painting is being displayed for two weeks.
In the answer choices, we're looking for a flaw which parallels this one. That means the correct answer needs to present two sufficient conditions which lead to the same necessary condition, and then arbitrarily conclude that an item meeting the necessary condition also meets one of the sufficient conditions, incorporating both sufficient-necessary confusion and an arbitrary selection between two options.
8.
The flawed pattern of reasoning ██ ███ ████████ █████ ████ ███████ █████████ ████ ██ █████ ███ ██ ███ ██████████
a
The city council ████ ████ ██████████ █████████ ██ ██████ ███ ████ ████ ███ ███ ███ ████ ███████ ████████ ██████████ ██ ████ ██ ███████ ███████ █████████████ ███ ███ ███████ ███████████ █ ████ ██ ███ █████ ███████ ███████ ████ ██ ██ ████ ███ ██ ██ ███ ███████ ████
(A) does have two sufficient conditions (existing structure and planned development) leading to the same necessary condition (on the map). However, this argument's flaw is that it fails to recognize that a sufficient condition has been triggered: the development in (A) is an existing structure, so will be on the map.
To match the flaw from the stimulus, (A) would need to identify a structure that will be on the map, and then arbitrarily conclude that it is either an existing structure or a planned development. That would be the right combination of sufficient-necessary confusion and arbitrary choice.
b
The city map ███ ████████ ████████ ██████ ████ ███ ████████ ██████ ██████████ ███████ ██ ███ ███ ████ ████ ████ █████████ ██████ ██████████ ██ ███ ███████ ████ ███ ████ ██ ██████████ ████ █ ████ ████ ██ ███ ████ ████ ████ ████ █ ██████ ████████ ██ ████ ████ ██ ███ █████
(B) doesn't have two sufficient conditions leading to the same necessary condition, which diverges from the stimulus' structure. Instead, (B) fails to consider that a condition which was once sufficient to establish something is a public building (a blue dot) may no longer be sufficient, since public buildings are now marked differently.
A better version of (B) would say that both blue and purple dots marked public buildings. It would then identify a public building, and arbitrarily conclude that it would be marked by either a blue or purple dot. That would match the stimulus.
c
I have just █████████ ███ ███ ████ ████ █████ ██████ █████████ ████ █████████████ ███ ██████ ██ █████ █████ ███ ████ ██████ █████ █████████ ███████ ████████ ████████ ██████ ██ ██████ ██ █ ██████ █████ ████ ██████ ██ ██ █ █████████████ ██ ███ █████████ ████ ████ ████ █ ████████
There's no flaw in (C). Given that the legend says that thoroughfares are marked by solid lines rather than dotted, it’s logical to conclude that the mapmakers made a mistake by marking a thoroughfare with a dotted line.
d
On this city ████ █ █████ ████ ██████████ ███ ████ ███████ █████ █████ ████ █████████ █████ ██████████████ ██ █████ ██ ██ ███ ██ ███████████ ███████ █ ██████████ █████ ████ ██ ███ ███ ██ █ ████████████ ██ ██ █████████ ██ ███ ████ ███████
(D) doesn't commit sufficient-necessary confusion, which it would need to match the stimulus. Instead, (D) establishes two items that share a common characteristic—being marked with a solid line—and assumes that there’s no other way of determining which item a particular solid line represents.
e
The legend on ████ ████ ███ █████████ ████ ██████████ █████████ ███ ██████████ ██ ██████ █████ █████████ ███ ████ ██████████ ██ ██████ █████ █████ ██ █ ██████ ███ ██ ██████ ███████ ██ █████ ████ ██ █ ████████ ██ ██████ ███████
(E) presents two sufficient conditions leading to the same necessary condition: both monuments and hospitals are marked with purple dots. (E) also arbitrarily concludes that an item meeting the necessary condition must meet one of the sufficient conditions: a purple dot is taken to mean a hospital, without any reason to think it's not a monument—or another building. (E) matches both elements of the flaw in the stimulus.