There are so many themes in TGCF, some imparting wisdom and some imparting inspiration, and all of which I love.
I know people have varying opinions on what the central theme is. (Reblog or comment with what you think it is, or with your favorite one!) I personally think that it is to stay true to your core principles, no matter what.
Xie Lian's famous line, "body in abyss, heart in paradise," reflects this, though the first time he said it, he had not actually experienced it. This line outraged and offended Jun Wu because he himself did not attain this, and thought it was impossible.
And in order to justify it by proving that anyone would abandon their principles and succumb to cynicism and despair under similar circumstances to his (and also to "gain a successor" and a sympathetic companion), he tries again and again to get Xie Lian to abandon his. He does this by assisting nature in thwarting Xie Lian's efforts to save Xianle, trying to ruin his cultivation path (Land of the Tender), creating a scenario in which his former subjects cause him the worst torture imaginable, and leaving him to wander the world luckless and unable to die.
But Xie Lian never does abandon them, despite the gargantuan temptations and reasons to do so. The course of the story is his experience of "body in abyss," and regaining a "heart in paradise" despite it. At the climax of the novel is this scene: "Will you change? Will you change?" "I won't! I won't! I won't!"
The second biggest theme, IMHO, is something I haven't figured out how to put into words yet; perhaps that love can set you free. Its motif is how Xie Lian's external shackles are an analogy for his internal ones that have still remained even after 800 years, of obligation/duty, negative self-view, shame/regret/penance, Jun Wu's influence, and more... and how Hua Cheng's love starts loosening them, and then finally breaks them, both externally and internally.
The Chinese apparently sometimes use the phrase "may all taboos be shattered" to mean "do whatever you want." Hua Cheng once said this to him, essentially telling him, shatter your taboos. And over the course of their time together, he does. His shackles shatter and his taboos shatter, both largely because of Hua Cheng. I wish I knew who had said this, but my favorite fan saying about the book is this: "The story is about Xie Lian's journey, and how he learned to love himself again, through the effort of a man who never had loved himself."
(In real life, this love doesn't necessarily have to be from another person or entity. People can grow to learn to love themselves, and free themselves from their own shackles.)
But again, there are so many more. So many depths to explore.
