Logical ReasoningDifficulty: Hard

PT102 S2 Q20 Explanation

Physicist: Determinism is the view

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

TopicsFlaw

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Stimulus

Physicist: Determinism is the view that every event has a preceding cause sufficient for its occurrence. That is, if determinism is true, then the events that are presently occurring could not have failed to occur given the state of the universe a moment ago. Determinism, however, is false because it is impossible the position and velocity of any given subatomic particle at a particular time.

What this question is testing

Flaw

Your task

Describe the reasoning error the argument actually commits.

Common trap

Answers that name a real logical flaw the argument doesn't actually make.

Winning move

Articulate the gap in the reasoning yourself, then match it to the choice that describes that gap.

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

The question
20.

The physicist’s reasoning is most vulnerable to criticism on which one of

Answer choices

  1. Bad Conclusion Match6% picked this

    That it is impossible to measure accurately both the position and velocity of any given subatomic particle does not imply that it is impossible

    This answer is structured like this: That X is true does not imply that Y is true We're always objecting that, "the fact the evidence is true does not imply/prove the conclusion". Does the evidence match X and the conclusion match Y? Yes, the evidence was saying "it's impossible measure both the position and velocity of any given subatomic particle". But, no, the conclusion wasn't saying "it's impossible to know the position or velocity of all subatomic particles". The conclusion was saying, "It's not the case that every event has a preceding cause sufficient for its occurrence / events presently occurring could have failed to occur given the state of the universe a moment ago".

  2. Premise / Conclusion Reversed14% picked this

    That the complete state of the universe at any given time is unknowable does not imply that the states at that time of the

    This answer is also structured like this: That X is true does not imply that Y is true So we want to know, does the evidence match X and the conclusion match Y? Did the evidence say "the complete state of the universe at any given time is unknowable"? Yes, the Intermediate Conclusion said that, and it is evidence for the Main Conclusion. Did the Main Conclusion say "the states of the individual subatomic particles making it up are unknowable". No. The premise was saying something like that. This answer essentially is saying, "The fact that the intermediate conclusion is true doesn't imply that the premise is true". That would never be an objection we would make. We only care whether premises imply conclusions, not whether conclusions imply premises.

  3. Bad Conclusion Match13% picked this

    That it is impossible to measure accurately both the position and velocity of any given subatomic particle at a particular time does not imply

    This answer is also structured like this: That X is true does not imply that Y is true So we want to know, does the evidence match X and the conclusion match Y? Did the evidence say "it's impossible to measure both position and velocity at a particular time"? Yes, that's the premise. Did the author use that to support a Conclusion that says, "position or velocity cannot be measured separately"? No. The author used it to support the conclusion that says, "It's impossible to know the complete state of the universe at any given time."

  4. Correct63% picked this

    That it is impossible to know the complete state of the universe at any given time does not imply that there is no complete

    Why this is right

    This answer is also structured like this: That X is true does not imply that Y is true So we want to know, does the evidence match X and the conclusion match Y? Did the evidence say "it's impossible to know the complete state of the universe at any given time?" Yes, that's the Intermediate Conclusion.. Did the author use that to support a Conclusion that says or assumes, "there is no complete state of the universe at a given time". Sigh. Yes, kind of? Determinism is based on the idea that the complete state of the universe at moment X determines the complete state of the universe at moment Y. The author is trying to refute this idea by saying, "How could that be true? After all, it's impossible for us to know the complete state of the universe at moment X" And this answer is saying, "Sure, it's impossible for us to know the complete state, but there still is a complete state. Our lack of knowing it doesn't prove it doesn't exist. So determinism could still be correct." This answer is written in a frustrating style that is pretty hard to hear as correct if you haven't already thought through your objection to the argument. If you want to see a similar example, try this one.

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

  5. Bad Conclusion Match5% picked this

    That the position and velocity of any given subatomic particle cannot be jointly measured with accuracy does not imply that this is the case

    This answer is also structured like this: That X is true does not imply that Y is true So we want to know, does the evidence match X and the conclusion match Y? Did the evidence say "it's impossible to measure both the position and the velocity of a particle at a particular time"? Yes, that's the premise. Did the author think that idea implied that "it's impossible to accurately measure the position and velocity of all particles at a particular time"? No. The author used it to support the conclusion that says, "It's impossible to know the complete state of the universe at any given time." But in addition to this answer not matching the reasoning move the author made, the reasoning move this answer describes doesn't sound bad. If we say, "It's impossible to know whether any particular M&M has rat poison in it", then it's it fair to say, "Thus it's impossible, for all M&M's, to know whether they have rat poison in them"? It sounds like a self-justifying truth, but either way it's not a reasoning move our author made.

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