What metaphors are used in The Story of Edgar Sawtelle: A Novel by David Wroblewski?

Sometimes, an author will look to metaphorical language to put across a certain philosophical outlook of a character or even the overall perspective of the book itself. One of those occasions is the following example in which the narrator first presents a wide perspective and then narrows the focus ever so slightly:

“So much of the world was governed by chance…Life was a swarm of accidents waiting in the treetops, descending upon any living thing that passed, ready to eat them alive. You swam in a river of chance and coincidence.”