For the sake of the plot

Question

In my Sanskrit dictionary, the Latin phrase metri causa ("for the sake of the metre") is used to alert the reader to forms which may be used irregularly in order to fit the metre. For example, in the available literature, a verb might occasionally be conjugated in the wrong voice for metrical reasons, and this irregular usage would be highlighted in the dictionary entry for the root in question.

I was wondering if there exists a formulation that would mean "for the sake of the plot", as when something happens in a novel apparently purely to advance the plot and which feels forced and poorly motivated. If not, can we coin one?

Using some online dictionaries (one, two), the two possibilities for "plot" that I came up with are argūmentum and āctiō, giving us argūmentī causa and āctiōnis causa as possible translations of this phrase (if my declension skills are to be trusted (by which I of course mean, if Wiktionary's declension skills are to be trusted.))

The dictionaries suggest that argūmentum is more commonly used for plays and its English daughter 'argument' makes it seem like a risky choice to me. Āctiō also seems to be used more of drama and its closeness to 'act' is tangible, although apparently they are not directly related. It seems like the better choice, though, as the dictionary defines it as inter alia:

the action, the connection or series of events, the plot

which seems quite suitable.

However, my two years of Latin were ever such a long time ago, so I'd welcome the input of somebody more familiar with the actual language, in order to get something that seems natural. I'd be especially interested if anybody can point to an actual formula that might have been used, either by the Romans themselves, or later European writers.

(P.S.: This is more for my own amusement, I wouldn't use contrived Latin phrases in a real essay, I'd stick to plain English or bona fide Latin phrases (see what I did there?))

Answer 1

I'd avoid both argumenti causa, for the reason brianpck states in his comment to your question, and actionis causa, which refers to the basis of a lawsuit.

A quick search suggests that the phrase narrationis causa, though not found in Classical Latin, appears a few times in Medieval and later Latin—"for the sake of the story." Which strikes me as fairly apt.

Answer 2

An oblique answer:
The Romans borrowed loads of Culture from the Athenians, including the words for theatre, scene, episode, ...and the MACHINE.

The machine could be trundled out (Some historians say lowered on a crane) with a feast or a heap of dead bodies or anything surprising really.

If the plot got really tangled up, and the playwright couldn't see any way of sorting it out, they could wheel out The Machine with a suitable god on board to sort things out. Hence, any resolution of the plot which was unnatural, improbable, and out of character could be referred to as a

Deus ex machina.

noun: deus ex machina (Google Search.) an unexpected power or event saving a seemingly hopeless situation, especially as a contrived plot device in a play or novel. late 17th century: modern Latin, translation of Greek theos ek mēkhanēs, ‘god from the machinery’.

The term the OP was looking for was an adjectival phrase to describe a deus-ex-machina-type solution. I offer a noun to use in apposition instead..
And here for comparison is Merriam Webster

Answer 3

I actually think argumenti causa is the best option. Suetonius uses the word in a very similar context:

[Nero] inter cetera cantavit ... Herculem insanum. In qua fabula fama est tirunculum militem positum ad custodiam aditus, cum eum ornari ac vinciri catenis, sicut argumentum postulabat, videret, accurrisse ferendae opis gratia.

"Among other parts, Nero sang that of Hercules in his madness. In which play the story goes that a novice recruit appointed to guard the gates, when he saw Nero in costume and bound with chains, as the plot demanded, ran up to give help."