The Annoying Friend in the Car: A Rule for Diagramming Logic Games
Recently I was in the car with some friends. I was sitting in the backseat and wasn’t driving. The person who was driving didn’t know where she was going. The person sitting in the passenger seat was supposed to be navigating for her, and he was doing an absolutely horrible job. I could tell he was driving her nuts. This is the kind of stuff he was saying:
Okay, you need to make the third right up here. I mean you could turn right before it, like now, but you don’t have to—oh, wait, you did. Okay, so now that we turned here, hmm. Well, we could keep going straight or we could take the next left, but we’ll need to end up taking a right eventually—why did you take a right?! No, I said we need to eventually! Since we’re now going back the other direction, we could take a right or a left, but somehow we have to turn around…
See how annoying that is? As it was happening, I thought of logic games (because I’ve been doing this way too long). It seemed like a great illustration of a very important logic games principle. When it comes to diagramming, do not write what could be true and what must be true all in the same place. That is, don’t mix up what has to be true with what might be true.
In the same way that it is confusing to receive driving directions that mix what could happen in with what has to happen—“we could turn here but have to turn before four streets up but we could also turn on the next street”—it’s confusing when you look at a diagram where slots 2 and 3 are filled with the letters M and R, but M has to go in slot 2 and R could go in slot 3.
For this reason, it’s best only to write in what must be true, and save what could be true for side diagrams, or “clouds” as we call them at Manhattan LSAT (bubbles with possibilities listed in them)—basically, any diagramming tactic that denotes “this is different from what must be true…this is only what could be true.”
If you’re used to writing it all in one place, it may take some time to break the habit. But start now. It’s worth the struggle.