Hi LSAT,
Thanks for the question! The thing about this concept is that it appears very frequently on the LSAT. So much so that it's a concept you have to become comfortable with, and one that isn't tipped off by a certain setup or game type. The general idea is one where a set of variables (often 2 or 3) is taking up space in some manner without actually being assigned. That's the basic condition for the principle to be in play, and that happens
a lot.
It's also a concept that often really comes up in the endgame of doing individual questions, but you can also see it come on the radar during the scenario when you get rules such as:
- A and B must be in different groups.
Exactly two of D, E, and F are selected.
G and H cannot perform after each other.
Each of those rule types are about some oppositional relationship where the presence of one negatively affects the presence of other variables. That's what creates that "rotating" aspect where you got one of a pair of variables taking up space but you not being able to pin down exactly which variable it is (or 2 of 3 variables taking up space, etc).
Probably my favorite game to display how the concept works is PT16, September 1995, Game #1 (8 students divided into 3 classes). It's by no means the only game, but there are several questions in the middle of the game that are essentially a tutorial on how this concepts operates.
Please let me know if that helps. Thanks!