LSAT 91 - Section 2 - Question 10

This is a Main Point question.

The argument in the stimulus contains a lot of complications. First we get the context. Then we see the word “however,” which introduces the transition from context to argument. The argument itself contains a sub-premise supporting a major premise supporting the main conclusion. And on top of all that, it uses the contrapositive argument form.

The context tells us that radioactive elements may have been created when the universe began. The next sentence says “however,” which indicates the transition over to argument, followed by “even if that were true,” which indicates that the information in the context is “throwaway.” We don't really care whether radioactive elements were created at the beginning of the universe, because what we really care about is that radioactive elements are still being created today. And that's the main conclusion. How do we know that? Well, it's the rest of the stimulus that provides the support. Let's skip the next sentence and instead jump to the last sentence, which contains the contrapositive argument. The sufficient condition is introduced by the word “if.” If no new radioactive elements have been created after the universe began, then there would be almost no radioactive elements left in the universe today. Next, we fail the necessary condition. There is an abundance of radioactive elements in the universe today. This allows us to contrapose on the conditional and draw the failure of the sufficient condition as the conclusion. New radioactive elements have been created since the universe began. Okay, so that's good but it's still been billions (13.7) of years since the universe began. How do we know that new radioactive elements are still being created today?

That's where the middle sentence comes in. That sentence does two things. One is that it explains why we should believe the conditional to begin with. It’s support. If you are skeptical about the if-then statement, you can consult this middle sentence. The reason why if no new radioactive elements are being constantly created, then we would run out of radioactive elements is explained by the middle sentence. It's because radioactive elements are really unstable so within a few million years all of them would've disappeared. That's the minor premise that acts as support for the major conditional premise. The other is precisely to fix the timing issue. It's saying that radioactive elements only live for a few million years so the ones we're seeing today can't be that old (in universe time), like at oldest, it's only a few million years old. That's still not today, but it does bring it billions of years closer to today.

Answer Choice (A) would be the correct answer choice to an MSS question. It says that any radioactive element created at the beginning of the universe has probably decayed into other nonradioactive elements. This is supported by the minor premise, which sets a time limit of at most a few million years for decay.

Correct Answer Choice (B) is the most accurate paraphrasing of the main conclusion.

Answer Choice (C) is the major conditional premise.

Answer Choice (D) is the context of the argument.

Answer Choice (E) is the middle statement, which plays the role of minor premise (explaining the major conditional premise) and major premise (fixing the timing issue).