LSAT 102 – Section 2 – Question 20

LSAT 102 - Section 2 - Question 20

June 1998

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Question
QuickView		 Type Tags Answer
Choices		 Curve Question
Difficulty		 Psg/Game/S
Difficulty		 Explanation
PT102 S2 Q20
+LR
Flaw or descriptive weakening +Flaw
Lack of Support v. False Conclusion +LSvFC
Fact v. Belief v. Knowledge +FvBvK
A
6%
165
B
8%
158
C
9%
160
D
73%
167
E
5%
164
147
156
166
 +Harder 148.204 +SubsectionMedium

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 to know the complete state of the universe at any given time since it is impossible to measure accurately both the position and velocity of any given subatomic particle at a particular time.

Summarize Argument: Counter-Position
The physicist concludes that determinism (the view that every event is guaranteed by the state of the universe immediately before) is false. This is supported by the fact that it’s impossible to know the entire state of the universe at any given time. In turn, that claim is supported by the impossibility of measuring both the position and the velocity of subatomic particles at the same time.

Identify and Describe Flaw
The flaw in this argument is that the physicist mixes up the factual state of the universe with human knowledge about the state of the universe. Just because we can’t know everything about the universe at any given time, that doesn’t disprove the idea that there can be a complete and determined state of the universe.

A
That it is impossible to measure accurately both the position and velocity of any given subatomic particle does not imply that it is impossible to know either the position or velocity of all subatomic particles.
Like (C), the physicist doesn’t rely on the idea that it’s impossible to know either the position or velocity of all subatomic particles. The physicist’s point is just that we can’t know both of those things at the same time.
B
That the complete state of the universe at any given time is unknowable does not imply that the states at that time of the individual subatomic particles making it up are unknowable.
This gets the argument backwards. The physicist claims that the states of particles are unknowable to imply that the complete state of the universe is unknowable—which is totally reasonable.
C
That it is impossible to measure accurately both the position and velocity of any given subatomic particle at a particular time does not imply that its position or velocity cannot be accurately measured separately.
Like (A), this isn’t a flaw because it isn’t an assumption the physicist actually makes. The physicist’s point is that we can’t ever know both of these things at the same time. Whether we can know one or the other is irrelevant.
D
That it is impossible to know the complete state of the universe at any given time does not imply that there is no complete state of the universe at that time.
This is the flaw, because the physicist only focus on our knowledge about the universe, but draws a conclusion about the factual state of the universe. Without a link between knowledge and the factual state of the universe, the conclusion isn’t supported.
E
That the position and velocity of any given subatomic particle cannot be jointly measured with accuracy does not imply that this is the case for the position and velocity of all subatomic particles.
This just isn’t the case—if no individual particle’s position and velocity can be measured at the same time, then of course the position and velocity of all particles can’t be measured at the same time.

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Section 1 - Reading Comprehension

Section 2 - Logical Reasoning

Section 3 - Logical Reasoning

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