Only an expert in some branch of psychology could understand why Patrick is behaving irrationally. ███ ██ ██████ ██ ███████ ██ █████ ████ ██ █████ ███████ ████████ ████████ ███████ █████ ██ ██████ █ ████████ ██ ███ ███ ██████████ ████████
To identify a valid conclusion, our first step is fully understanding the stimulus. These claims are all we have to work with, so we want to be sure to really pin them down. The stimulus makes three claims:
1: if someone understands why Patrick is behaving irrationally, that person must be an expert in some branch of psychology;
2: if someone is an expert, they must not be certain of being able to solve someone else's problem; and
3: Patrick wants to come up with a solution to his own behavioral problem.
Notice that the first two claims are conditional statements. And if we diagram them, we can also see that they form a chain:
1: understands Patrick's behavior → psychology expert
2: expert → /certain of solving another's problem
chain: understands Patrick's behavior → psychology expert → /certain of solving another's problem
One likely candidate for a conclusion that must be true is the conditional chain formed by the first two claims. We can draw conclusions both from condensing the chain, and from taking its contrapositive:
condensing: understands Patrick's behavior → /certain of solving another's problem
contrapositive: certain of solving another's problem → /psychology expert → /understands Patrick's behavior
Just because we have a prediction, we shouldn't close ourselves off to other possibilities. The correct answer could also be the contrapositive of a single claim in the stimulus, or could relate to Patrick wanting to solve his own problem. In any case, the correct answer will have to be true based on the stimulus. Any answer choice that could be false will be incorrect, even if it could also be true.
Which one of the following ███████████ ███ ██ ███████ █████ ████ ███ ████████
Patrick does not ██████████ ███ ██ ██ ████████ ██ ████ ████
The stimulus tells us that only a psychology expert could understand Patrick's behavior. So (A) would be guaranteed if we knew Patrick wasn't a psychology expert. Unfortunately, the stimulus never says that, so (A) could be false.
Patrick is not ██ ██████ ██ ███████████
(B) has the same problem as (A), it just gets there faster. The stimulus doesn't say whether Patrick is a psychology expert, so (B) could be false.
Patrick is not ███████ ██ █████ ████ ██ ██████ █ ████████ ██ ███ ███ ██████████ ████████
(C) has two problems. First, we don't know if Patrick is a psychology expert, so we don't know if it's even relevant that
Second, even if Patrick were an expert, his behavior isn't someone else's problem. It's possible that experts (or even non-experts) can be certain of solving their own problems. We don't know, so (C) could be false.
Unless Charles is ██ ██████ ██ ████ ██████ ██ ███████████ ███████ ██████ ███ █████ █ ████████ ██ ███████████ ██████████ ████████
What do we know about psychology experts? They're the only people who might understand Patrick's behavior, and they are uncertain of being able to solve someone else's problems. However, we don't know who "should" offer solutions or not, including whether only experts should offer solutions. That's why (D) could be false.
If Charles is ███████ ██ █████ ████ ██ █████ ███████████ ██████████ ████████ ████ ███████ ████ ███ ██████████ ███ ███████ ██ ████████ ██ ████ ████
(E) expresses the contrapositive of the conditional chain we can construct using the
chain: understands Patrick's behavior → psychology expert → /certain of solving another's problem
contrapositive: certain of solving another's problem → /psychology expert → /understands Patrick's behavior
(E) applies the contrapositive of this chain to Charles: if Charles is certain of solving Patrick's (someone else's) problem, that implies he must not be an expert. And if Charles isn't an expert, he must not understand Patrick's behavior. This makes (E) a valid conclusion that must be true.