LSAT 90 – Section 2 – Question 17

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Type Tags Answer
Curve Question
PT90 S2 Q17
Necessary assumption +NA
+Harder 146.031 +SubsectionMedium

This is an NA question.

The stimulus opens with context that the premises call upon with a referential phrase. To establish a human colony on Mars, it requires the presence of a tremendous quantity of basic materials on Mars. And then we need to assemble those materials. The premise states that the costs of transporting those materials through space would be very high. Therefore, the argument concludes that it wouldn’t be economically feasible to establish a colony on Mars.

The assumption is that the costs in the premises are a consideration that matters. What are those costs again? Costs of “transporting material through space.” Now, why would we need to transport materials through space? Because a Martian colony requires a tremendous amount of basic materials. But again, why must we transport that “tremendous amount of basic materials” through space? The assumption is that those materials cannot be found on Mars.

This is absolutely necessary for the premises to even matter to the conclusion. This is what Correct Answer Choice (E) says. That Mars isn’t a practical source of the basic materials required for establishing human habitation there. If Mars were, then there’d be no need to transport those materials through space.

(E) seems pretty obvious once you get there. But the hard part is in getting past the other trap answers.

Answer Choice (A) is one such trap. It uses “only if” to lay out a necessary condition for establishing human habitation on Mars: the decrease in cost of transporting materials from Earth to Mars. This sounds good but it isn’t necessary. First, note that the conclusion didn’t claim that it would be physically impossible to colonize Mars. Rather, just that it would be economically infeasible. Economically infeasible means highly unlikely, but it doesn’t mean impossible. Economic constraints are softer than physical or technological constraints. Economic constraints are a matter of collective resource allocation. Physical or technological constraints are imposed by what knowledge we have access to. Second, note that the premises cited the costs of transportation through space. Surely Earth to Mars is through space but so is the moon to Mars. And so is the asteroid belt to Mars. If the materials aren’t even coming from Earth in the first place, then why should we care about the transportation costs of Earth to Mars?

Answer Choice (B) is another trap. It says that the cost of transportation through space (note already the improvement upon (A)) isn’t expected to decrease in the near future. Again, this sounds good. Don’t we need the costs to not decrease? Well, first notice that (B) isn’t about what will actually happen to the costs. It’s about what we expect to happen to the costs. We don’t need expectations to point in any particular direction. We need actual costs to not decrease. Second, even if actual costs decrease in the near future, the argument can still survive as long as the costs don’t decrease too much. For example, imagine if the costs decrease by 0.01%. That’s presumably not enough of a decrease to make a difference. In order to hurt the argument, we need to have the costs decrease to the point of being economically feasible to transport enough basic materials to Mars.

Answer Choice (C) claims that Earth is the only source of basic materials necessary for a Martian colony. This is a classic Strengthen answer in an NA question. If (C) were true, then that definitely helps the argument. Earth is the only source of raw materials and therefore, to get those materials to Mars, we must transport them through space. But this isn’t necessary. What if one of Mars' two moons had the requisite materials? That would still require transportation through space and so the argument would still survive. (C) isn’t necessary.

Answer Choice (D) says that no significant benefit would result from establishing a human colony on Mars. This isn’t necessary. The argument didn’t express a value judgment. It wasn’t about the pros and cons of establishing a Mars colony or whether we should do it. It was just an argument about the costs and economic feasibility of such an endeavor. (D) is not only unnecessary, it is also irrelevant.

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