What are the chances that two tiny lifeboats, in the middle of the ocean, each with a blind man in control, would meet? You might say the odds are pretty low, and you would be right. However, in Life of Pi, the author creates this very scenario. It seems so unbelievable that it must be symbolism. When Pi encounters the blind man, it symbolizes guilt.
When Pi first meets up with the blind man, he believes he is talking to Richard Parker. so he asks him, "I'm curious, tell me - have you ever killed a man?" After talking a bit, the voice, whoever it is, answers the question with a yes. He says he has killed "a man and a woman", and later saying "the man first the woman second." Well, the end of the book Pi tells a short version without the animals, where the cook killed the sailor and Pi's mom. That's a man and a woman, so this leads me to believe he is talking to the cook.
But Pi killed the cook, as seen when he confesses: "Then we fought and I killed him." It's plain and simple; the cook died. So how is Pi talking to the cook if he is dead? Remember that Pi is blind. So he doesn't actually see the other man, who is blind as well. It sure is convenient to go blind, right? Well, that could be symbolism, too. Your eyes symbolize your soul, so Pi going blind could symbolize that he had some regret or guilt that he thought was troubling his soul. Maybe the blind man was blind too because he was feeling guilt. Although when Pi asks him "Any regrets?" he answers with "It was them or me", and tries to close the subject. I think the blind man (or Pi himself) really was regretful about what he had done, and just tried not to show it.
I don't think the blind man was real; it was just Pi's imagination, his guilt for killing the cook. The blind man tries to kill Pi, which would have been Pi being overcome by guilt. But Richard Parker kills the blind man, which could be Pi's survival instinct kicking in. The point is, the blind man was symbolizing Pi's guilt for killing the cook.
