What I call the divergent method is when you start with all the characters in the same time and space—an Aristotelian structure. After that you can follow them individually whereever they go—as long as you’ve seen them all together at one point, right at the beginning. That allows you to pungently characterize these people in relationship to one another in time and space: physically, we get to see them standing next to each other and judge how they carry themselves, but also emotionally, how they relate to one another. Once the audience has that imprint, if it’s well done, then the film is free to have different points of view […]
The opposite approach is convergent: two or three stories that start separately and then flow together. The English Patient is a good example. It starts out with two mysterious figures in a plane, flying across the desert. The plane gets shot down by the Germans and then—cut—you’re on a train, with a young woman, a nurse, in a completely different situation: bantering with wounded soldiers. The two stories appear to have nothing to do with each other, but the audience trusts that these two rivers are going to come together.
Film editor Walter Munch talking about storylines.