Stone Monkey (Symbol)
Monkey is born out of stone, which symbolizes his lack of fear and attachment to things. Because of his circumstances, he has no family or parents from the very beginning, which helps explain his later behavior and generally brave or reckless nature.
The Journey (Allegory)
The entirety of the novel is an extended allegory for the pilgrimage that believers take towards Enlightenment, which can only be successfully completed through cooperation.
Tripitaka's Flaws (Symbol)
Tripitaka, despite being the chosen monk, exhibits many human flaws throughout his journey. He continually falls for the demons' disguises and is shown to be less bright than Monkey. This aspect of Tripitaka's characterization symbolizes the idea that humanity is imperfect, and that learning is a life-long process.
Monkey's Fate at the Mountain of Five Elements (Symbol)
Monkey is continually portrayed as inferior to Buddha, and nowhere is this more evident than in their exchange at the Mountain of Five Elements, where Buddha imprisoned Monkey. Despite being arguably the best and brightest that the world has to offer, Monkey is unable to overcome the great Buddha. His fate at the Mountain symbolizes the inability of man to equal Buddha, demonstrating the need for the quest for enlightenment.
Government vs. Religion (Motif)
In Chapter 8, the second marshal that Kuan-yin and Hui-yen encounter speaks of several cautionary proverbs. One specifically warns that the government will flog you to death if they get hold of you, and that Buddhists will starve you to death if they get hold of you. There is an underlying motif that, no matter which way you turn, neither the government nor your religion alone can save you.