Although Wu Cheng-en was a Confucian scholar, he wrote this book for entertainment. ... If we insist on seeking some hidden meaning, the following comment by Hsieh Chao-chih is quite adequate: "The is purely imaginary, belonging to the realm of fantasy and miraculous transformations. Monkey symbolizes man's intelligence, Pigsy man's physical desires. Thus Monkey first runs wild in heaven and on earth, proving quite irrepressible; but once he is kept in check he steadies down. So this is an allegory of the human mind, not simply a fantasy."
Wu Cheng'en