ZMD: I'm reminded of the darcs revision control system and its patch theory. Given patches A and B applied in order (AB), it's possible to calculate two commuted patches A' and B' that when applied in the opposite order (B'A') produce the same result. If you did A, did B, and want to undo A, you commute the patches, and then take A' away from A to walk you back to B'.

That's really only an illustrative analogy, but it's a good one. You could see the algorithm here as "commute the decision to the front and delete it". So taking your example, the original was "decide, and leave, and become an individualist". The commuted version is "leave, and become an individualist, and decide". Then delete the decision. You're re-deciding in the context of the rest of the status quo as a given. "Given I have left and I have become an individualist, would I now decide to leave?".

Thinking of it that way is a bit brain-twisty, but it makes sense.