This poem takes two seemingly disconnected realms of ideas and superimposes them onto one another: Mythic religion, and baseball. One might say that an incidental argument is formed that, if someone takes their hobby seriously, they can sort through their religious beliefs in real time, by getting excellent at something. This is certainly implied in the climax, because Ethan's baseball skills help him to defeat Coyote.
Notice that Coyote is not a demon from hell. He is an animal. That represents Ethan's true obstacle, which is his limited animal nature and his instincts. Just as the coyote has teeth to kill and consume, so does Ethan. Just like the animal succeeds more in a group than in alone, so does Ethan. They are really not so different, except for one regard: Ethan loves baseball in a way the coyote doesn't love anything. This is evidence that Ethan has something sacred about him—hence the mythic, heroic form of epic poetry.
The symbolism about good and evil is obvious, and the dilemma with nature can be seen through the coyote metaphor, but there is something implied in the novel that is not so obvious. Look at the Tree of Life: Why does that tree serve as a gateway between the realm of literal reality (the baseball diamond, for instance) and the metaphysical, religious realm of Ethan's imagination? His fascination with trees is a sign of his own animal nature, but it also suggests that what Ethan really wants in life is to be happy, like a monkey in a tree with infinite fruit.
