Jackson on the final scene

"The Grapes of Wrath ends not with an event, a “plot development” or twist, but with a scene. This final scene is not a resolution of the conflict for the Joads. We know that they will be further hurt by their own and other men's illusions. The scene is rather a resolution for the reader, who has been taken in tow by the narrator to witness one set of conditions after another. It is almost as if we as readers had been shown a series of slides recording “that which happens” in this environment and that. The resolution, significantly, is one for the observer, rather than for the observed. No novel, it seems to me, could operate more in the spirit of science than this."

The rationale behind this fiction would seem to lie in the fact that scene most clearly and directly expresses the condition of what “is.” Thus, plot moves from condition to condition, and the structure of Steinbeck’s novels usually involves contrast and parallel of condition, almost musical in its contrapuntal patterning.
(ibid.)

Benson, Jackson J. “John Steinbeck: Novelist as Scientist.” NOVEL: A Forum on Fiction 10.3 (Spring 1977): 248-264, 261.