What are some major symbols in the story A Separate Peace?

I would argue that the most important symbol
in the novel is the tree. Gene is drawn to it when he returns to Devon in
the first chapter, and his description reflects on the influence of the tree on his
childhood. He describes as though it is a monster that tormented him as a child, but
upon returning, he realizes it is nothing of which to be afraid. The tree
has Biblical symbolism- Finny's fall represents the loss of innocence among the boys.
When Gene pushes Finny, not only does he lose his innocence by committing
an act of violence, but he cause Finny to lose his by shattering his ideal world.
To a lesser extent, WWII is also a symbol for loss of innocence in the
novel. It connects back to the shattering of Finny's world, which
connects back to the tree itself.

The weather is also a
symbol in the novel. The weather directly reflects Finny's influence on
Gene. When Finny and Gene are happy, and Finny is living his ideal
existence, it is summertime. The boys have few obligations, the rules of Devon have been
relaxed for the summer session, and there's an idyllic atmosphere to the school. Yet
when Finny is gone from Devon, and after he dies, it is winter. There is a coldness, the
war has come to the school, and Gene no longer has the friendship of Finny to guide
him.