I’m taking this as our starting point because a grasp of form is a powerful tool. Form in art is not a dead thing, not a stenciled outline to be colored in. Rather, form is a thought that has evolved over a long time, in a particular culture, about what works – in this case, what works as a satisfying shape of a story for readers in our culture.
A short story in its simplest form works something like this: it is one scene involving two characters, one of whom is the protagonist, the other the antagonist. The protagonist is the character whose mind we’re closer to – often the narrator. For some time before the story actually begins, the protagonist’s old way of facing the world – her old set of values, her habitual method of dealing with the challenges life hands out – has not been working very well.
When we meet her, the protagonist is on the edge of a situation in which her old way will come under such pressure that a change of some kind will be absolutely demanded. She will face a challenge she doesn’t know how to meet. Push will come to shove, and that crisis will be the climax of the story. The person who puts on the pressure, for purposes of the story, is the antagonist. The term antagonist is used in a technical sense; that character need not antagonize in the everyday meaning of the word. As much pressure could be generated by falling in love with the protagonist as by holding her up at gunpoint.
The story reaches its climax through a series of lesser crises, in each of which the protagonist’s old way becomes less and less successful, and the pressure to change becomes greater; it ends when the protagonist responds to the critical challenge – which is not to say that she necessarily meets it successfully. If she has an “aha!” moment of sudden enlightenment and perfect action at the moment of crisis, and therefore lives happily ever after, there’s a great risk that the story will end up seeming shallow and sentimental. Anything can happen, ranging from the ideal “aha!” to the bleakest failure even to notice that the moment for action has come.
(I learned this way of putting it from Alex Gold, with whom I taught in Harvard’s Expository Writing Program.)
You can download this as a Word document here: form of the short story