The foremost philosopher of abduction, Charles Sanders Peirce, summarized abduction as follows:Noting that abduction is the opposite of cause-and-effect - the effect is observed, and a cause suggested - the article goes on to describe the relationship to roleplaying games.
The surprising fact, C, is observed;
But if A were true, C would be a matter of course,
Hence, there is reason to suspect that A is true.
For instance, assume the surprising circumstance that my car won't start this morning. If it were true that my car battery were dead, then the fact that my car won't start would be a matter of course. So there is reason to suspect (abduce) that my car battery is dead.
The art of abduction depends on having a set of "weird facts", that is, a circumstance you need to explain. Fortunately, such facts are never in short supply. Indeed, the easiest and most accessible method of brainstorming available to any gamemaster is random generation of facts.I've been doing this for as long as I've played, but I never knew it had a name.