Life of Pi recounts the story of Piscine Molitor Patel, mercifully known as Pi. You can read
the plot overview on Wikipedia; I'm not going to reinvent the Wiki wheel. I will, however, highlight particular events that will lead us to the worldview embedded in this confusing, compelling story.
As a boy, Pi’s mother raises him as a Hindu. When he is fourteen, he begins to follow the teachings of Christianity and then of Islam, believing them all capable of teaching him something important about God. So, Hindu/Christian/Muslim. His father, a champion of reason, notes, "If you believe in everything, you believe in nothing." That's solid advice, but Pi seems far more motivated to embrace ideas based on personal experience, strong feelings and intuition. As a result, he does confusing things like a) embrace three contradictory notions of God and b) try to pet a tiger by luring it closer with a piece of raw meat. Think of these two events as related.
When his family and a bunch of their zoo animals head for Canada
(read Wiki), a storm capsizes the ship, leaving Pi stranded on a lifeboat with a zebra, a hyena, an orangutan, and a tiger named Richard Parker (the one he once tried to feed). Eventually only the tiger remains, and it is not inclined to share the space.
Pi ties a raft to the side of the lifeboat, and thus begins the heart of a mesmerizing story as they float for 227 days, fighting each other and the elements, surviving storms and carnivorous islands, and eventually making peace before finally landing on the shore of Mexico.
Insurance company representatives visit Pi in the hospital to find out what happened. They don’t believe his incredible story, so Pi quietly tells them a much darker one. It’s a horrible story of human atrocity, with a murderer and cannibal (the hyena) who preys upon Pi’s mother and another sailor (the zebra and orangutan) while Pi (the tiger) waits too long to intervene, then becomes a violent killer to destroy the evil on the boat. They believe that one.