Flaws: Mistaken Reversal (TM)

PowerScore has trademarked a remarkable number of terms that have become standard LSAT jargon, including the term “Mistaken Reversal (TM).” This logical error was identified more than two thousand years before PowerScore trademarked the name, however. Aristotle listed “affirming the consequent” as one of the thirteen original fallacies. Whatever we call this error, it shows up whenever you find this pattern:

• If you live in Detroit, you live in Michigan
• Therefore, if you live in Michigan, you live in Detroit.

This error is obvious when you use an intuitive example involving geography, but it is less obvious in other contexts. Don’t let that keep you from looking for it every chance you get–this little error is easy to slip into an argument and hard for the untrained eye to spot. That means you’ll see lots of these errors in easy-to-medium flaw questions.

You’ll see this answer choice often, but it may be the hardest answer to make sense of. The LSAT writers often use abstract terms that tend to paralyze the student. While it is possible to decode these baffling answers and demonstrate that they describe a “mistaken reversal (TM),” it is very hard to do that with the clock ticking and your future on the line. That’s why it is so important to learn to identify this and other flaw answers before test day.

Here are some examples of answers that describe this particular flaw. (These are not actual LSAT answers, due to copyrights, but they are inspired by and similar to real answers):

• “It mistakes a situation that must be present to establish the validity of the conclusion for a situation that would guarantee the validity of the conclusion.”
• “It treats a requirement for a pig to fly as something that ensures that a pig will fly.”
• “It takes a necessary condition for an argument’s failure to be a condition that would guarantee the argument would fail.”
• “Concludes, from the fact that X occurred and that Y would ensure that X occurred, that Y must have occurred.”

In most cases, the answer simply states that somebody has mistaken a necessary condition for a sufficient condition. Until you become familiar with the underlying problem and the way the LSAT writers word these “mistaken reversal (TM)” answers, these can be baffling. After you recognize the problem and the pattern, they become quite simple.