Terentian comedy is a style based on the work of Roman playwright Terence. Basically it sets up a pattern of introduction, complication and resolution that will be familiar to most readers and movie watchers (even if the terms that go along with it aren’t).
All ancient drama begins with the protasis in which the basic problem of the story is set up. In a Terentian comedy this almost always has to do with love between two young people which is opposed in some way. Traditionally, one set of parents or the other object to the partner their child has chosen – perhaps the girl’s birth is not established so it isn’t clear whether she is well enough born to be acceptable to the hero’s parents – but the key thing is that there should be something hindering the pair being married (in Sleepless in Seattle, the hindering object is the distance between Meg Ryan and Tom Hanks, for instance). The couple are helped towards realizing their desires by friends: a role usually played by a clever servant or slave in traditional comedy. A plot develops to get the couple together.
Epitasis happens towards the middle of the action of the play, and provides complication. The plot is discovered by the parents, perhaps, or derailed in some other way, and the couple are parted (She sees him, unobserved. He is hugging another woman. She leaves, heartbroken, and refuses to take his calls). For most of the rest of the action things look black for happy resolution, the couple are unhappy, their friends despair, it seems that things cannot go right.
This is solved by the catastasis. Some new information comes into the piece that allows the resolution to follow. Perhaps a new character arrives on the scene (going back to the example we opened with, the girl’s father arrives appears and turns out to be completely acceptable or maybe it turns out that the woman the girl saw her lover embracing earlier was his sister).
The catastrophe (now often called denouement, since the original word has developed almost exclusively tragic connotations) plays out as a result of the catastasis. The couple is reunited, their love is consummated, and everyone lives happily ever after.
Hey, why change a formula that has worked for centuries?