Self-study
Support Tanya would refrain from littering if everyone else refrained from littering. ████ ██ ███ ███████ ███████ ███ █████████ ███ ████ ███ ██████ ███████
Method of Reasoning
The first premise in this argument is a conditional statement: if everyone refrained from littering, then Tanya would, too. The second premise is that the sufficient condition is partially met—some people (Tanya’s friends) don’t litter. The author then concludes that the necessary condition is true.
Identify and Describe Flaw
We can’t conclude that a necessary condition is true based only on the knowledge that the sufficient condition is partially satisfied! If we knew that everyone refrained from littering, then we could conclude that Tanya refrains, too. But we only know that some people refrain, so we have no idea whether Tanya litters or not.
19.
Which one of the following ████ ██████ █████████ ████ ███████ ██ ███ ██████ █████████ ██ ███ ████████ ██████
a
All residents of ███ ████ ████████████ ████ ████ █████ ██ ███████ ███ █████ ██ ████████████ █████████ █████ ████████████ ████ ██ █ █████ █████ ██ ████ █████ █████████ ██ ████ ████████████ ████ █████ ████ █████
Wrong flaw. This argument erroneously concludes that, because all residents share some goals, one of their specific goals must be shared. That isn’t the flaw from the stimulus, though—here, there’s no sufficient condition that’s only partially met.
b
If a talented ██████ ██ ███████ ██ ██████ ███ ███ ███████ ████ ███ ███████ ██████ ████ ███ ██████ ██ ██████████ ██████████ ███████ ███████ ████ ███ ██████ ██ ██████████ ██████████ ███ ███ ██ ███████ ██ ██████ ███ ███ ███████ ██ ███ ████ ██ █ ████████ ███████
Wrong flaw. Unlike the stimulus, (B) does not use a partially satisfied sufficient condition to conclude a necessary condition; rather, it uses a partially satisfied sufficient condition and a fully satisfied necessary condition to conclude the other part of the sufficient condition!
c
Herbert will stop ███████ ██████ ████████ ██ ███ █████ ██ ████ ██ ███ ███████ █████████ ██████████ ████ ██ ███ ███████ █████████ █████ ████ ████ ███████ ████ ██████ █████████ ██ █████ █████████ ████ ███ █████████
Wrong flaw. Unlike the stimulus, (C) never reaches a conclusion about whether the necessary condition from the conditional premise will be satisfied—it doesn’t say that Herbet will stop selling office supplies. Rather, (C) simply states that some of Herbert’s customers won’t complain if he does stop selling office supplies, because they didn’t know he ever did (this isn’t a perfect argument, because they could still learn about it and complain, but it’s not the same flaw from the stimulus).
d
If all whales ████ ██ ███████ ███ ████ ████ ██████ ████ ██ ████ ██ ████████ ████ ██████ ███ ██████ █████████ ██ ████ ████ ███████ ███ ████
This is the cookie-cutter flaw of confusing necessary and sufficient conditions. The author provides a conditional statement as a premise, tells us the necessary condition is satisfied, and then concludes that the sufficient must be true—a big flaw! But it isn’t the same flaw from the stimulus, where the author concludes that the necessary condition is true based on a partial satisfaction of the sufficient.
e
If all of █ ████████████ █████████ ████ ███ █████ ██ ████ ██ ██ ███████████ ███████████ ████████ ████ ███████ █████████ █████ ███ ████ ██ ████ ██████ ██ ██ ████ ██ ██ ███████████ ███████████
The first premise in this argument is a conditional statement: if all of a restaurant’s customers like its food, the restaurant is exceptional. The second premise is that the sufficient condition is partially met—some people (those Sherryl consulted) liked the food. The author then concludes that the necessary condition is true. This is the same flaw from the stimulus, where the author also concludes that the necessary condition is true based on a partial satisfaction of the sufficient.