No action or scene in the play was to be a digression; all were to contribute directly in some way to the plot.
A novel differs from a play in that it has (at least) three different levels of action. I am likely to come back to these, so I'm going to define them in a little detail here:
- book – historically a physical object, the book includes (in addition to the story) all the additional or peripheral information that goes with the experience of reading, such as cover art, blurb, author bio, dedications, and all the baggage that the reader brings along with him, such as his past experiences of the same author or the same genre.
- story – the story is the emotional experience provoked or evoked by reading the book; this is the reader's engagement with characters, locations and events depicted in the book. This is highly dependent on the author's stylistic skill, as well as his skill in getting emotional experience across to the reader, both in terms of the experiences of characters, and in terms of the emotional experience that this generates in the reader himself.
- plot – the "mechanics" underlying the story; how the course of events is influenced devices and desires of different characters, or by the vicissitudes of fate or fortune. A plot may be developed or designed in various ways, but it is a different skill from narration or characterization.
But the editor (and the author) has to be aware that what might be redundant to the plot could be crucial to the story. Imagine two characters need to be fleshed out a little, so that the reader is more comfortable with their actions later on in the story. The author has an opportunity to place them in a little vignette - let's say they spend half an hour chatting in a café. Now suppose the book's title is 'The Cafés of Montmartre'. This vignette may have nothing to do with the plot, but everything to do with both the story and the book.
Often, therefore, the author needs to take a decision as to how he will prioritize the three levels of action. A coffee-table book about the lives of famous Mormons (yes, really), will likely prioritize the book; presentation, layout, organization and referencing, as well as the physical experience of reading it (whether in print or on a function-rich tablet) are important to reader satisfaction. A romantic journey of self-discovery will likely prioritize the quality of emotional experience, therefore elements relating to the story. A romantic comedy, however, is much more concerned with careful control of the plot. When the author is clear about his priority, it becomes much easier to identify the real redundancies and also, crucially, identify what is absent, and how to turn redundancies into features.
Let's go back to that pavement café in Montmartre. Supposing that this book is actually one of those French novels where you start out thinking it is a sort of harrowing kitchen-sink weepy, but gradually the sensation steals over you that it is turning into a thriller. You could take that redundant half-hour conversation in a café and prolong it by a crucial five minutes. This results in one of the characters being absent somewhere that he was expected to be present, and the rest of the book is a sort of conspiracy to try to get events to catch up with where they ought to have been.
In a thriller I finished editing not long ago, a character introduced for sound plotting purposes is killed, also for sound plotting purposes - the main character has to look for a new place to stay as a direct result. But after that point, the dead guy had no further consequence or influence on either story or plot, and that got me thinking about what I think of as the next level of Unity of Action, which is reader satisfaction.
Reader satisfaction is a slippery chimera (probably part eel rather than snake). It's like a target you can aim for; the more you practice, the more often you hit.
There are various ways of aiming for it; but if your priority is plot, then it's worth going further than just avoiding redundancy. It's worth using every event for as much consequence as possible, at as many levels as possible.
There's a technique used by standup comics that goes under a number of names, that works by the comic making some throwaway gag early on in his routine, that he then recalls, unexpectedly but with scrupulous justification, much later on. This technique is a major source of audience satisfaction and is analoguous to a basic technique of tight plotting: every action has a consequence; every event drives every other event. In the case of the dead guy forcing the hero to look for new lodgings, that's a dead guy you've got there. The reader is expecting it to have other consequences. The reader will be pleased with himself if it has the consequences he is expecting (someone tries to blackmail the hero, or uniform comes knocking). But to aim for the bullseye on the reader satisfaction target, the recall should be something that the reader isn't expecting. I love when authors do that. I'm sure I'm not the only one.
So, like yesterday, Aristotle's Unity of Action is a yardstick or a proofing technique: it helps the author and the editor to identify both weaknesses and opportunities. However I think that while the Unities of Time and of Place are useful proofing options, I think the Unity of Action is an essential and profound one. It helps the author to a deeper understanding of his own work, and hence helps him to better provide reader satisfaction.