Humans' emotional tendencies are essentially unchanged from those of the earliest members of our species. Accordingly...

Naz on October 2, 2015

Great job identifying that this is a strengthen with necessary premise question!

As such, make sure to remember that a premise is necessary for a conclusion if the falsity of the premise guarantees or brings about the falsity of the conclusion. First we check to see if the answer choice strengthens the passage, and then, if it does strengthen, we negate the answer choice to see if its negation makes the argument fall apart. If the answer choice does both those things then it is our correct answer.

Conclusion: Humans are generally unable to choose more wisely than their ancestors.

Why? We are told that human emotional tendencies are essentially unchanged from those of the earliest members of our species, despite the fact that technology makes possible a winder range of individual and societal choices than in centuries past.

Let's look at answer choice (E). Does it strengthen the argument?

Yes.

Answer choice (E) states that if humans are now able to make wiser choices than in centuries past, then an essential change has taken place in their emotional dispositions (remember that "only if" indicates a necessary condition).

(E): MWC ==> CED
not CED ==> not MWC

We are told that human emotional tendencies are essentially unchanged, i.e. not CED.

P2: not CED

So, this triggers the contrapositive of answer choice (E) to conclude humans are not making wiser choices, i.e. the conclusion of the argument is strengthened.

Now we must negate answer choice (E). How do we negate a Sufficient & Necessary statement? We show that the sufficient condition can exist without the necessary condition:

Negation of (E): humans are now able to make wiser choice than in centuries past even if an essential change has not taken place in humans' emotional dispositions.

So, if it is not necessary that essential changes take place in humans' emotional disposition, then the argument no longer stands since we use the fact that "humans' emotional tendencies are essentially unchanged from those of the earliest members of our species," as evidence that humans are generally unable to choose more wisely.

Therefore, answer choice (E) is the correct answer.

Hope that helps! Please let us know if you have any other questions.

Hannah-Anderson on September 25, 2019

@Naz This was a really helpful explanation, thank you!

amf on April 21, 2020

Can you please explain why D is incorrect?

Abigail-Lee on October 14, 2020

^^