GMAT Tip of the Week: Say It Ain't So

The only way to successfully complete “Weaken” critical reasoning questions on the GMAT is to find alternate explanations for the conclusion.

Do you see a flaw in that sentence?  You should – and you can, using the very conclusion proffered above.  Finding alternate explanations isn’t the “only way” to successfully complete those questions; you could guess correctly, you could eliminate answer choices that are out of scope of the conclusion, you could identify the flaw in the argument and find an answer choice that exploits that flaw…  But arguably the most effective way to solve these problems is to find an alternate explanation – like we just did in demonstrating alternative ways to solve these problems correctly.

Meta-example aside, as you read Weaken questions, you should recognize that there are plenty of alternate explanations for any set of facts that don’t necessarily include the conclusion that the author is trying to convince you must be true.  As an example, consider this weaken question from the Official Guide for GMAT Review, 12th edition:

Robot satellites relay important communications and identify weather patterns. Because the satellites can be repaired only in orbit, astronauts are needed to repair them.  Without repairs, the satellites would eventually malfunction.  Therefore, space flights carrying astronauts must continue.

Which of the following, if true, would most seriously weaken the argument above?

Now, before we even consider the answer choices, it’s helpful to already get in the mindset that the conclusion is incorrect – or, as the title of the post here says, “Say It Ain’t So”: set your mind to the idea that the conclusion is wrong, and it’s your job to show why.  The author is trying to tell us that we MUST send astronauts to space to fix these satellites, because in order to be repaired the satellites need humans to go up and make the fix.  Well, what other alternatives do we have that don’t involve manned space flights.  How about:

  • We can just send up new satellites instead of fixing the old ones
  • The satellites might “eventually” malfunction but that could be far enough down the road (20 years? 30 years?) that by then we’ll have better satellites and we wouldn’t need to fix the old ones
  • New technology is being developed that will replace the need for robot satellites before they are expected to malfunction

There are plenty of potential situations in which we wouldn’t NEED TO send up astronauts.  And by starting to think about those we can better solidify in our minds that the conclusion is not necessarily true.  [Remember: for a conclusion to be logically valid it "must be true".] So by setting our minds to “no, that’s not entirely true” and starting to think about other factors that might prove it false, we’re ready for the correct answer, which is:

(E) Technical obsolescence of robot satellites makes repairing them more costly and less practical than sending new, improved satellites into orbit.

Choice E is written technically, but hits many of the themes that we predicted…”new technology”, “send up new satellites instead”, etc.  By creating the mindset that “this conclusion isn’t true”, we’re much more receptive to the kinds of potential premises that would help us achieve that goal, to weaken the conclusion.

Now, keep in mind that you don’t have to accurately predict the right answer, and you shouldn’t spend more than 10-15 seconds trying to brainstorm all possibilities.  The mere act of embedding “that’s not necessarily true” in your mind and thinking along those lines of “and I can prove it’s not true” is what whets your appetite for the correct answer.  Ultimately what’s important is to read critically and be skeptical of the conclusion so that you’re ready to pounce on an answer that fits with your mindset.  Embrace your job as an argument critic — it may not be “the only” way to solve these problems, but it’s quite often the best way.

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