Pi's whole identity is strongly shaped by religion. A deeply spiritual person, he seeks a higher truth and isn't particularly fussy about how he attains it. Whether it's through Christianity, Hinduism, or Islam, it's not the path that matters but the final destination.
Throughout his life, Pi has taken various bits and pieces from the three great religions, all of which have contributed in some way towards his spiritual identity. From Hinduism, he's developed a powerful connection to the natural world, with which he feels a strong affinity. Hinduism has also inspired in him a profound sensitivity to the beauty of creation. When he attends a Catholic service, Pi comes to appreciate the story of Christ, which he finds both beautiful and morally uplifting. Further spiritual enlightenment comes from Islam, the rudiments of which Pi is taught by Mr. Kumar, who tells him that it's the religion of the beloved.
Pi's syncretism, his combining of different religious traditions to form a harmonious unity, is unusual for someone of his time and place. Many of the people he encounters are actively hostile towards his veneration of three different religious traditions. But Pi persists in his spiritual endeavors, as he derives great wisdom and understanding from them.