You've probably heard the old adage that there are truly no original stories; only tellings. In other words, nothing is truly original in itself - only in its execution.
Great literature, theatre, film and television generally works with universal truths that have been handed down through generations of storytelling. These truths are like debates that have a central theme of some kind which leads to a foregone conclusion - or, occasionally, subverts what we believe to be true in order to have an unexpected outcome. These truths have been called many names - most commonly, "Theme" or "Premise".
We have chosen to use the word "Premise", because it inherently offers a proposition that is assumed to lead to a conclusion. This, then, forms the basis of the story arc. And it's the writer's job to either confirm or confound this premise in their story.
When our writers compose a pitch, we insist that they either choose one of the well-established premises or create a new one of their own. The premise will then give shape to their story by insisting that a presupposition is formed in the audience's mind and then debated by the narrative. The conclusion will generally confirm the premise - but not always. However, it helps to give the story shape, so that the audience know where they are headed.