What is a literary element to support a thesis for "Big Two-Hearted River"?

This short story by Ernest Hemingway is both subtle and
complex. Numerous literary elements work together to achieve the development of Nick's
character and the theme of the narrative. Of these literary elements, the theme of the
story is most effectively realized and communicated through symbolism. The story's title
points the reader to the two central symbols in the story: the two very different areas
of the river in which Nick can fish--one clean and appealing, the other dangerous and
deep. Nick avoids the deep water, just as he works hard to avoid remembering his recent
experiences in the war. Thus the "two-hearted" river assumes symbolic meaning,
representing Nick's conscious and subconscious
selves.

Subtle clues in the story suggest where Nick has
been and the destruction he has seen. Others indicate that Nick is making a conscious
effort to focus on the immediate present; when his mind strays, he deliberately "chokes"
his memories. He could not control what had happened to him in war, but he can control
how he deals with its aftermath, and at this time in his life he chooses not to deal
with it at all. He will confront his painful memories of the war in his own time, just
as he will fish in the deep and dangerous part of the river when he is
ready.

Thus the symbolism in the story supports several
thesis statements, one being a primary theme in much of Hemingway's work: A man cannot
control the forces that act to destroy him, but he can endure and face life with
discipline, courage, and dignity. The symbolism in "Big Two-Hearted River" develops this
theme.