Logical ReasoningDifficulty: Medium

PT154 S4 Q26 ExplanationCurrent evidence indicates that there

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

TopicsSufficient Assumption

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Stimulus

Current evidence indicates that there is no methane on Planet 253. If that is the case, it is certain that there is no life on Planet 253. Since microbes always produce then there are no microbes.

What this question is testing

Sufficient Assumption

Your task

Find the assumption that, if added, guarantees the conclusion follows.

Common trap

Answers that only partly bridge the gap, leaving the conclusion unproven.

Winning move

Identify the new term in the conclusion and pick the choice that links it to the evidence.

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

The question
26.

The conclusion drawn above follows logically if which one of the following

Answer choices, explained

  1. Unrelated to Goal4% picked this

    There is, in fact, no methane on

    This doesn't mention "life" so it's immediately wrong. The conclusion of this argument was a conditional statement: if there's no methane, then there's no life Whenever we encounter conditional conclusions, we will never be trying to strengthen or weaken the idea that the trigger is true. Suppose I made this conditional conclusion: if humans colonized Mars, we would build roller coasters there. You can't strengthen this by saying that we will colonize Mars or weaken this by saying we won't. I'm not saying we're actually going to colonize Mars. I'm only making a definitive claim "we would build roller coasters" about a hypothetical world in which we have colonized Mars. So when we see a conditional conclusion, we just accept the Trigger as an implicit premise. You can only debate my roller coaster conclusion if you first just accept the supposition that this is a world where we've colonized Mars.

  2. Unrelated to Goal9% picked this

    If methane exists on Planet 253 then we would be able to

    Since this doesn't mention "life", we can immediately reject it.

  3. Unrelated to Goal4% picked this

    If there is no methane currently on Planet 253 then there has never been methane

    Since this doesn't mention "life", we can immediately reject it.

  4. Correct78% picked this

    If there are no microbes on Planet 253 then there is no life

    Why this is right

    This is what we predicted. The evidence told us this: if no methane, no microbes This answer adds on this: if no microbes, then no life which allows us to derive the conclusion: If no methane on P253, then no life on P253

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

  5. Unrelated to Goal6% picked this

    If there is methane on Planet 253 then there must be life

    This mentions "life", but this is a rule that is set up to prove "there is life". We need a rule that proves there isn't life.

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