The term ‘diegesis’ (and derived adjectives ‘diegetic’ and ‘non-diegetic’) comes from film criticism, but has been used recently in RPG critique. In essence, diegesis defines the narrated world relative to the viewer (or in our case, the player). This is somewhat of a heady, academic definition, so let me give an example. In a movie, the soundtrack is typically non-diegetic. That means that the music playing that the audience hears does not interact with the narrative, with what’s going on on the screen. In some cases, though, the soundtrack is diegetic, meaning that the events of the narrative do interact with the music. The perfect example of that would be musicals: The soundtrack you hear is in fact the characters breaking into song, that is part of the narrative and the world.

And just like musicals, roleplaying games are creating assumptions about their worlds that do not align with the real world. You are never going to suddenly hear a musical cue and break into song while waiting for a bus; similarly you will never find yourself suddenly able to rebuild an engine or speak Mandarin because you were able to invest ‘skill points’. These aren’t bad things: both dramatic works and games are designed in service to their goals as art and entertainment, not to be ‘realistic’ or ‘grounded’. On the other hand, there is a vast world of critical opinion around how much the conceits of both films and games live in either diegesis or exegesis (the realms of the narrative and the audience, respectively); calling musicals divisive would be putting it mildly, and the same can be said about RPG mechanics which treat the characters more like narrative game tokens than extensions of the player.