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A Logic Lesson!

A Logic Lesson!

With some real world applications

Hannah Stella's avatar
Hannah Stella
Jan 31, 2023
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A Logic Lesson!
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When I used to tutor the LSAT, there were two Logical Reasoning question that confused every one of my students. For those unfamiliar with the LSAT, it is a logic test that requires little to no specialized knowledge (though an extensive English vocabulary and general understanding of Latin and Greek prefixes and suffixes is helpful). Logical Reasoning questions account for about half of the LSAT and they all follow the same format. A short paragraph of text, often with a logical fallacy or jump in logic included, is followed a question that tests the reader’s understanding of the logical structure of the paragraph and then five multiple choice answers to the question presented.

This has nothing to do with logic but look how beautiful Berry Islands, Bahamas is!

Let’s do one together from the LSAC website. (And stay with me here, I have a point that isn’t about law school or this silly test or anything like that.)

Laird: Pure research provides us with new technologies that contribute to saving lives. Even more worthwhile than this, however, is its role in expanding our knowledge and providing new, unexplored ideas.
Kim: Your priorities are mistaken. Saving lives is what counts most of all. Without pure research, medicine would not be as advanced as it is.
Laird and Kim disagree on whether pure research
  1. derives its significance in part from its providing new technologies

  2. expands the boundaries of our knowledge of medicine

  3. should have the saving of human lives as an important goal

  4. has its most valuable achievements in medical applications

  5. has any value apart from its role in providing new technologies to save lives

In this example, Laird and Kim agree that pure research is important and do not disagree about whether each other’s priorities are important. They only disagree about which priority is most important. The answer is 4, because Kim believes that medical advancement is the most important result of pure research while Laird disagrees because he believes the most important result is finding new ideas and generally expanding knowledge.

The point of this question is to test whether the reader understands the subtlety of the disagreement, neither Laird nor Kim thinks the other’s point is unimportant, they simply disagree about which point is most important. Which means that they agree more than they disagree. They are both advocating for the same thing, for the value of “pure research”. It can be difficult to notice agreement when we’re focusing on disagreement. To understand this question, we need to understand how much common ground the two have.

But that was a relatively easy LSAT question.

…

Let’s take a look at the two questions that every one of my students was confused by- because they are confusing. I think the underlying logic as value in daily life. I think understanding these questions makes us smarter people who are able to look at situations with more nuance and understanding. (I sound like a real party man right now but my girls, please stay with me.)

The first is about an astronaut. It describes a rocket launch with over 1,000 small steps, tiny gears, pieces of technology that needed to operate successfully in order for the astronaut and his rocket to launch, orbit the earth, and return safely. Each of these 1,000+ tiny technologies is extremely unlikely to malfunction, each has a 99.5% chance of functioning correctly. Therefore, the whole mission is safe, because each step in the mission is safe.

The question asks if the conclusion that the mission is safe is correct. It is not.

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