Well, Richard Parker really represents Pi's subconscious. A major idea in this novel is that we all have a duality, a dual nature. We have the life we live and we have the life we want to live-- and existence happens somewhere in the middle. Reality for Pi, the harsh, cruel, and gruesome nature of humanity, is not his reality or his truth, so he creates his own. He creates a world that makes sense, a world with a good and evil dichotomy that he can comprehend and live with. Richard Parker is the manifestation of his fears.