story premise

An author should be able to state the premise of every story he/she submits. By premise I mean the hypothesis or argument or assertion or insert-your-term here of the story. You should be able to summarize your story's essence in one sentence. For example, right now I'm working on a story which has the premise: a man has to travel to another planet to learn the true nature of love.

If you can't do this for your story then your story is not finished.

Now, I'll be honest with you. In my example that wasn't the exact idea I started with. My process (and everyone has a unique process) is I *think* I know the beginning, middle, and end of my story before I start writing and so I write the first draft. I read what the result says. Usually it says something somewhat different from what I thought it was going to say. I have to decide on the story premise. I revise, including cutting all the stuff that doesn't support the premise. Sometimes I have to add a bit. The point is to create a coherent story.
Your method will differ from this. But... you must ask yourself:

What is your story premise?