Logical ReasoningDifficulty: Medium

PT15 S3 Q6 Explanation

As far as we know, Earth

A free, expert breakdown of this official LSAT Logical Reasoning question.

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Stimulus

As far as we know, Earth is the only planet on which life has evolved, and all known life forms are carbon-based. Therefore, although there might exist noncarbon-based life on planets very unlike Earth, our scientific estimates of the probability of extraterrestrial life should be generated from and the likelihood of carbon-based life on those planets.

What this question is testing

Strengthen

Your task

Find the choice that makes the argument's conclusion more likely to be true.

Common trap

Answers that are consistent with the argument but add no real support, or that strengthen a claim the argument doesn't make.

Winning move

Locate the gap between evidence and conclusion, then pick the choice that closes it.

Reading along? Open the full official question in LawHub — we show a fragment here and keep the reasoning in our own words.

The question
6.

Which one of the following general principles most strongly supports

Answer choices

  1. Opposite2% picked this

    There is no good reason to think that unobserved phenomena closely resemble those that

    This would be a great weakener. The author is assuming a correspondence between the life we've yet to observe and the life we have so far observed.

  2. Unrelated to Recommendation2% picked this

    A scientific theory that explains a broad range of phenomena is preferable to a competing theory that explains

    This recommendation is not about picking one scientific theory over another. It's just endorsing one method of calculating the probability of extraterrestrial life.

  3. Weakens15% picked this

    It is preferable for scientists to restrict their studies to phenomena that are observable and forego making

    The recommendation is about how we can make a good estimate about the unobservable presence of extraterrestrial life. This answer is saying we shouldn't make estimates about unobservable things.

  4. Unrelated to Recommendation5% picked this

    A scientific theory that explains observed phenomena on the basis of a few principles that are independent of each other is preferable to a

    This recommendation is not about picking one scientific theory over another. It's just endorsing one method of calculating the probability of extraterrestrial life.

  5. Correct75% picked this

    Estimations of probability that are more closely tied to what is known are preferable to those that are less closely

    Why this is right

    This is the only answer even giving us a principle for how we should estimate probability (which is what the recommendation is about), so this answer leaps out to the lead in terms of relevance. Was the method of estimation recommended tying its estimations to what is known? Sure! It was saying, "As far as we know, life can emerge on Earth-like planets with carbon-based life forms. So let's base our estimate on those two known properties."

    Skill tested: Strengthen · how this choice captures the argument's function is the move to repeat next time.

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