Each of the throughlines in a story can be seen as standing alone or as standing in relation to the other throughlines. When selecting which Classes to assign the throughlines of your story, it is extremely important to remember two relationships in particular among the throughlines:

The Objective Story and Subjective Story throughlines
will always be a dynamic pair

And…

The Main Character and Obstacle Character throughlines
will always be a dynamic pair

These relationships reflect the kind of impact these throughlines have on each other in every story. The Main and Obstacle Characters face off throughout the story until one of them Changes (indicated by the Main Character Resolve). Their relationship in the Subjective Story will help precipitate either Success or Failure in the Objective Story (indicated by the Story Outcome).

What these relationships mean to the process of building the Domains in your story is that whenever you set up one Domain, you also set up its dynamic pair.

For example, matching the Main Character throughline with the Universe class not only creates a Main Character Domain of Universe in your story, it also creates an Obstacle Character Domain of Mind. Since Mind is the dynamic pair to Universe in the Dramatica structure, matching one throughline to one of the Classes automatically puts the other throughline on the opposite Class to support the two throughlines’ dynamic pair relationship.

Likewise, matching the Objective Story throughline with Psychology to create an Objective Story Domain of Psychology will automatically create a Subjective Story Domain of Physics at the same time. The reasoning is the same here as it was for the Main and Obstacle Character throughlines. No matter which Class you match with one of the throughlines on the Dramatica structure, the dynamic pair of that class will be matched to the dynamic pair of that throughline.

From the Dramatica Theory Book