PrepTest 132, Section 4, Question 18
If there are sentient beings on planets outside(75 more words not shown)
The argument's conclusion can be(10 more words not shown)
- AThere are no(13 more words not shown)
- BAny beings that(19 more words not shown)
- CIf there is(30 more words not shown)
- DIf a sentient(24 more words not shown)
- EAny sentient beings(21 more words not shown)
Reading the argument
Why would the beings have to be as intelligent as we are? Couldn't we send a spacecraft, take pictures, and discover less intelligent creatures?
The next sentence blocks that idea. We won't be able to send spacecraft to planets outside our solar system anytime soon. Fine—but is a spacecraft the only way? What about a telescope good enough to detect signs of life? We haven't been told that every other method is ruled out.
The argument does give us a second route: communication. Any beings able to communicate with us in the near future would have to be at least as intelligent as humans. That covers discovery through a message from them. It doesn't yet cover discovery of beings that can't communicate with us.
What we’re looking for
To make the conclusion follow, close that remaining gap. If beings can't communicate, detecting them must require the spacecraft we can't send. Otherwise, another method could let us discover them despite their lower intelligence.
Working the answers
- A
The conclusion concerns planets outside our solar system. Eliminating other sentient life within our own system doesn't tell us how we could detect beings in another one. This changes the location instead of closing the gap about detection.
- B
Wanting to communicate doesn't establish being able to communicate. More importantly, this concerns intelligent beings who might send a message. Our unanswered question is whether we could detect less intelligent beings without a message from them. B leaves that route open.
- C
For the planets outside our solar system, we already know we can't send spacecraft soon. C extends a restriction to other planets with sufficiently intelligent beings, but it still says nothing about telescopes or other methods. Another restriction on spacecraft doesn't make spacecraft the only way to detect life.
- DCorrect
This closes the alternative route. Beings less intelligent than humans cannot communicate with us in the near future, according to the premise. Under D, detecting beings unable to communicate requires sending a spacecraft. And we cannot send one to planets outside our solar system in the near future.
So without beings intelligent enough to communicate, neither route is available. We can't receive communication from them, and we can't make the visit required to detect them otherwise. The telescope possibility is now ruled out for those noncommunicating beings.
- E
This says human-level intelligence is enough for communication. But giving intelligent beings that ability doesn't prevent us from detecting less intelligent ones by some other method. The conclusion needs to rule out those other routes, which is what D does.
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