Self-study
Even though MacArthur's diet book helped many people lose weight, Conclusion MacArthur should not have published it. ██ ███████████ ████ █████ ████████ ██ ██████ ███ ██████████ ████ ██ ███████████ ███████ ███ ██████ ██ ████ ███ ████████ ███ █████ █████████ ██ █ ██████████ ██ █████████ ██████ ████ ██ ██████ ████ █████ ████ █████ ███ ██ ██████ ███ ██████████ ███ ████████████
Summary
The author concludes that MacArthur should not have published his diet book. Why? It hurt the health of some of its readers, and MacArthur either knew or should have known this would happen.
Notable Assumptions
The argument features a prescriptive claim, but the premises only tell us facts. As such, the author assumes there is some link between the two. We need a conditional statement that bridges the gap between, phrased as “if premises, then conclusion.” This gives us a strong prediction:
If one either knows or should have known that their actions would hurt others, then they should not have done those actions.
7.
Which one of the following ███████████ ██ ██████ ████ █████ ██ ███████ ███ ██████████ ██████████
a
One should not █████████ ██ ██████ ██ ███ █████ ████ █████ ██ █████ █████████ ██████ ███ ██████ ██ ████ ███████
Wrong trigger. The premises tell us that MacArthur either did know or should have known his actions would hurt others, leaving open the possibility he didn’t know. As such, we can’t activate this conditional statement.
b
One should not ██████ █ ██████████ ██████ ███ █████████ ████ ███ ██ █████ ██ ███ ███ █████████ ██ ██████ █████ ███████
(B) leads to the wrong conclusion. We aren’t concerned with whether others should have followed MacArthur’s diet Advice. We only care whether MacArthur should have published the book in the first place.
c
One should publish █ ████ ████████████ ███████ ██████████████ ████████ ██ █████ ██ ██ ██████ ██ ███████ ████ ████████ █████ ███████ ████ ███████ █████
Leads to the wrong conclusion. If the sufficient and necessary conditions were swapped, this would support our conclusion; (C), however, only lets us prove a book should be covered, not that it shouldn’t.
d
One should not ███████ █ ████ ████████████ █ ██████████ █████ ██ █████████ █ ████ ██████ ███ █████ ████ ███ ██████████ █████ ███ █████ █████ ████ █████
Wrong trigger. We know that MacArthur’s book did succeed in its goal of helping people lose weight, so we can’t use this conditional statement.
e
One should not ███████ █ ████ ████████████ █ ██████████ ██████ ██ ██████ ██ ███ ██████ █████ ██ █████ ██ ████ ████ ██████ ████ ██████ ██ ██████ █████ ██ ████████████
MacArthur either did or should have known his book would hurt people. (E) tells us that, if that is the case, he shouldn’t have published his book. As such, (E) allows our conclusion to be properly drawn.