The through line, sometimes also called the spine, was first suggested by Constantin Stanislavski as a simplified way for actors to think about characterisation. He believed actors should not only understand what their character was doing, or trying to do, (their objective) in any given unit

Unit of action

Units of Action, or Units , were first suggested by Konstantin Stanislavski as a means of helping actors determine the through line or super objective of a role. A unit is a discrete piece of action in a play-text, marked by a significant change in action. This could be a change in what the...

, but should also strive to understand the through line which linked these objectives together and thus pushed the character forward through the narrative.