So first of all the stimulus states that we are dealing with an age old argument made by early astronomers: one which we now know to be incorrect. But our job is simply to choose an answer that contains information required for their argument (reasoning) to hold true. If we find an answer choice that we can negate and in turn ruin their argument, then that is the correct one. The early astronomers use a premise that “if stars were farther (more than a few million miles) away, the stars would have to move at tremendously great speeds” [MTFMA --> MTGS] to conclude “stars are not more than a few million miles away” [ /MTFMA ]. To arrive at this conclusion is simple: contrapose the premise. /MTGS --> /MTFMA. That is what correct answer (D) gives us….It affirms “stars do not move at tremendously great speeds” [ /MTGS]. In plain English, if (D) is negated and stars DO move at tremendously great speeds then the astronomers’ reasoning is all wrong about how far away the stars are. I hope I helped make this a little more understandable but if not you can check out this necessary assumption lesson: http://7sage.com/lesson/how-to-find-necessary-assumptions/
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http://7sage.com/lsat_explanations/lsat-70-section-4-question-25/
http://7sage.com/addons/
Either way, I'm sure someone will explain it here in a bit. I don't think many people are on at this time.
The early astronomers use a premise that “if stars were farther (more than a few million miles) away, the stars would have to move at tremendously great speeds” [MTFMA --> MTGS] to conclude “stars are not more than a few million miles away” [ /MTFMA ]. To arrive at this conclusion is simple: contrapose the premise. /MTGS --> /MTFMA. That is what correct answer (D) gives us….It affirms “stars do not move at tremendously great speeds” [ /MTGS].
In plain English, if (D) is negated and stars DO move at tremendously great speeds then the astronomers’ reasoning is all wrong about how far away the stars are.
I hope I helped make this a little more understandable but if not you can check out this necessary assumption lesson:
http://7sage.com/lesson/how-to-find-necessary-assumptions/